using libmagic in Emacs?

using libmagic in Emacs?

[joakim]

(This is probably a FAQ but my google skills seem to fail me)

There are some operations in Emacs which tries to do the same thing as
the "libmagic" library, which is the core of the "file" utility, does.

For instance, in "image.el" there is functionality to look at magic
numbers in image files.

Also, I often whish that files would open in Emacs with correct mode
more often when there is no file extension.

Would there be interest in an Emacs patch for libmagic, or is there some
obvious reason this havent been done yet? I envision this as being an
inteface with 2 implementations, a lisp fallback like today, and
libmagic if available. I did a libmagick wrapper for Ocaml using Swig
before so I have some familiarity with the API.

-- 
Joakim Verona

Re: using libmagic in Emacs?

[Stefan Monnier]

> (This is probably a FAQ but my google skills seem to fail me)
> There are some operations in Emacs which tries to do the same thing as
> the "libmagic" library, which is the core of the "file" utility, does.

> For instance, in "image.el" there is functionality to look at magic
> numbers in image files.

> Also, I often whish that files would open in Emacs with correct mode
> more often when there is no file extension.

> Would there be interest in an Emacs patch for libmagic, or is there some
> obvious reason this havent been done yet? I envision this as being an
> inteface with 2 implementations, a lisp fallback like today, and
> libmagic if available. I did a libmagick wrapper for Ocaml using Swig
> before so I have some familiarity with the API.

I think it's a good idea.  It may require some non-trivial changes on
the Lisp side, since libmagic's information is not quite the same as
what Emacs currently uses: we'll probably want to use libmagic to get
a MIME-type and then have a table mapping mime-types to major modes or
some such.


        Stefan

Re: using libmagic in Emacs?

[Chong Yidong]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>> Would there be interest in an Emacs patch for libmagic, or is there some
>> obvious reason this havent been done yet? I envision this as being an
>> inteface with 2 implementations, a lisp fallback like today, and
>> libmagic if available. I did a libmagick wrapper for Ocaml using Swig
>> before so I have some familiarity with the API.
>
> I think it's a good idea.  It may require some non-trivial changes on
> the Lisp side, since libmagic's information is not quite the same as
> what Emacs currently uses: we'll probably want to use libmagic to get
> a MIME-type and then have a table mapping mime-types to major modes or
> some such.

This development would probably have to take place in a separate branch.

Re: using libmagic in Emacs?

[joakim]

Chong Yidong <cyd@stupidchicken.com> writes:

> Stefan Monnier <monnier@IRO.UMontreal.CA> writes:
>
>>> Would there be interest in an Emacs patch for libmagic, or is there some
>>> obvious reason this havent been done yet? I envision this as being an
>>> inteface with 2 implementations, a lisp fallback like today, and
>>> libmagic if available. I did a libmagick wrapper for Ocaml using Swig
>>> before so I have some familiarity with the API.
>>
>> I think it's a good idea.  It may require some non-trivial changes on
>> the Lisp side, since libmagic's information is not quite the same as
>> what Emacs currently uses: we'll probably want to use libmagic to get
>> a MIME-type and then have a table mapping mime-types to major modes or
>> some such.
>
> This development would probably have to take place in a separate
> branch.

I will work in my local git repos, and publish a patch here, much like
the imagemagick patch and the xwidget patch. I can switch to bzr
whenever that works.

The core libmagic lisp api should, however, be rather stand-alone and
non-intrusive. Client code such as the image type recognition code can
then be ported sucessively.

-- 
Joakim Verona

Re: using libmagic in Emacs?

[Stefan Monnier]

>>>> Would there be interest in an Emacs patch for libmagic, or is there some
>>>> obvious reason this havent been done yet? I envision this as being an
>>>> inteface with 2 implementations, a lisp fallback like today, and
>>>> libmagic if available. I did a libmagick wrapper for Ocaml using Swig
>>>> before so I have some familiarity with the API.
>>> 
>>> I think it's a good idea.  It may require some non-trivial changes on
>>> the Lisp side, since libmagic's information is not quite the same as
>>> what Emacs currently uses: we'll probably want to use libmagic to get
>>> a MIME-type and then have a table mapping mime-types to major modes or
>>> some such.
>> This development would probably have to take place in a separate
>> branch.

I don't expect it to be too intrusive, so I think it can be done on the
trunk, tho of course, each step needs to be planned with care.

> I will work in my local git repos, and publish a patch here, much like
> the imagemagick patch and the xwidget patch. I can switch to bzr
> whenever that works.

That's fine as well.

> The core libmagic lisp api should, however, be rather stand-alone and
> non-intrusive. Client code such as the image type recognition code can
> then be ported sucessively.

I think it's OK to install the code in CVS as soon as the Lisp API to
libmagic is ready.  Once that is done, we can decide which next steps
to take.


        Stefan

Re: using libmagic in Emacs?

[Juri Linkov]

>> There are some operations in Emacs which tries to do the same thing as
>> the "libmagic" library, which is the core of the "file" utility, does.
>>
>> For instance, in "image.el" there is functionality to look at magic
>> numbers in image files.

image.el doesn't recognize some rare JPEG formats, so libmagic will be
useful here.

>> Also, I often whish that files would open in Emacs with correct mode
>> more often when there is no file extension.

libmagick could supplement `magic-mode-alist' and `magic-fallback-mode-alist'.

> I think it's a good idea.  It may require some non-trivial changes on
> the Lisp side, since libmagic's information is not quite the same as
> what Emacs currently uses: we'll probably want to use libmagic to get
> a MIME-type and then have a table mapping mime-types to major modes or
> some such.

gnus/mailcap.el contains a table mapping MIME-types to major modes.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Date: Tue, 18 Aug 2009 17:11:02 -0400
> Cc: Chong Yidong <cyd@stupidchicken.com>,
> 	Emacs Development <emacs-devel@gnu.org>
> 
> >>> I think it's a good idea.  It may require some non-trivial changes on
> >>> the Lisp side, since libmagic's information is not quite the same as
> >>> what Emacs currently uses: we'll probably want to use libmagic to get
> >>> a MIME-type and then have a table mapping mime-types to major modes or
> >>> some such.
> >> This development would probably have to take place in a separate
> >> branch.
> 
> I don't expect it to be too intrusive, so I think it can be done on the
> trunk, tho of course, each step needs to be planned with care.

So what is the rule for new features that can be installed on the
trunk at this time?  I thought only relatively minor and safe ones,
but this one seems to break that rule, at least in my book.  If this
one is okay, then why not something like bidirectional editing, for
example?

Maybe we should simply decide right here and now that Emacs 23.2 will
be delivered from the RC branch, and open the trunk for all changes,
even not-so-safe ones?

Re: using libmagic in Emacs?

[Stefan Monnier]

>> >>> I think it's a good idea.  It may require some non-trivial changes on
>> >>> the Lisp side, since libmagic's information is not quite the same as
>> >>> what Emacs currently uses: we'll probably want to use libmagic to get
>> >>> a MIME-type and then have a table mapping mime-types to major modes or
>> >>> some such.
>> >> This development would probably have to take place in a separate
>> >> branch.
>> 
>> I don't expect it to be too intrusive, so I think it can be done on the
>> trunk, tho of course, each step needs to be planned with care.

> So what is the rule for new features that can be installed on the
> trunk at this time?

The rule is: anything is possible, but ones that aren't simple and safe
need to get confirmation here first.

> I thought only relatively minor and safe ones,
> but this one seems to break that rule, at least in my book.

It looks pretty safe: the first step is to add the Lisp API, which
should not impact any other code (tho it may cause temporary build
failures, I guess).  After that, set-auto-mode (and/or image.el, ...)
will need to be tweaked to also take libmagic into account
when available.  This should also be fairly simple.

> If this one is okay, then why not something like bidirectional
> editing, for example?

I was thinking of bidi for Emacs-24, but if you have code ready for it,
and if it's not too intrusive, I'd be willing to consider it.

> Maybe we should simply decide right here and now that Emacs 23.2 will
> be delivered from the RC branch, and open the trunk for all changes,
> even not-so-safe ones?

Yes, that's pretty much where we're at, I think, yes.


        Stefan

Re: using libmagic in Emacs?

[Chong Yidong]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> I thought only relatively minor and safe ones,
>> but this one seems to break that rule, at least in my book.
>
> It looks pretty safe: the first step is to add the Lisp API, which
> should not impact any other code (tho it may cause temporary build
> failures, I guess).  After that, set-auto-mode (and/or image.el, ...)
> will need to be tweaked to also take libmagic into account
> when available.  This should also be fairly simple.

I don't think that sounds simple or safe; however, there's not enough
information to know for sure, until Joakim posts the patch.

>> Maybe we should simply decide right here and now that Emacs 23.2 will
>> be delivered from the RC branch, and open the trunk for all changes,
>> even not-so-safe ones?
>
> Yes, that's pretty much where we're at, I think, yes.

Actually, if people want to start including more intrusive changes, I
think we should cut a new branch from the current trunk.  This would
postphone the CEDET merge to 23.3.

Re: using libmagic in Emacs?

[joakim]

Chong Yidong <cyd@stupidchicken.com> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>>> I thought only relatively minor and safe ones,
>>> but this one seems to break that rule, at least in my book.
>>
>> It looks pretty safe: the first step is to add the Lisp API, which
>> should not impact any other code (tho it may cause temporary build
>> failures, I guess).  After that, set-auto-mode (and/or image.el, ...)
>> will need to be tweaked to also take libmagic into account
>> when available.  This should also be fairly simple.
>
> I don't think that sounds simple or safe; however, there's not enough
> information to know for sure, until Joakim posts the patch.
>
>>> Maybe we should simply decide right here and now that Emacs 23.2 will
>>> be delivered from the RC branch, and open the trunk for all changes,
>>> even not-so-safe ones?
>>
>> Yes, that's pretty much where we're at, I think, yes.
>
> Actually, if people want to start including more intrusive changes, I
> think we should cut a new branch from the current trunk.  This would
> postphone the CEDET merge to 23.3.

Please dont postpone CEDET on my behalf! That would feel terrible.

-- 
Joakim Verona

Re: installing features on trunk (was: using libmagic in Emacs?)

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: joakim@verona.se,  cyd@stupidchicken.com,  emacs-devel@gnu.org
> Date: Tue, 18 Aug 2009 23:21:13 -0400
> 
> > I thought only relatively minor and safe ones,
> > but this one seems to break that rule, at least in my book.
> 
> It looks pretty safe

As you see, even Yidong is not sure he agrees, and neither am I.

> I was thinking of bidi for Emacs-24

If history is of any significance, I may not live until Emacs 24.  And
for some strange reason, the burden of adding this feature seems to be
on my shoulders and no one else's: no development happened in this
direction for the last several years, even though most of the
low-level code was sitting on a branch (courtesy of Handa-san) for the
last 4 years.

So I'd prefer it to happen sooner rather than later, at least to the
point where the foundations are in place and others can contribute the
rest.

> but if you have code ready for it
> and if it's not too intrusive, I'd be willing to consider it.

It is not ``ready'' in the sense that it is not yet production
quality.  It does not yet support all the features of the Emacs
display engine.  But it can already display bidirectional text, for
now only in a left-to-right paragraph and only if the text has no
faces and overlays.  The code that reorders characters for display
isn't activated until you flip a buffer-local variable, and then only
in that buffer.  Is that ``not too intrusive'' enough?

next bugfix release? [was: Re: using libmagic in Emacs?]

[Dan Nicolaescu]

Chong Yidong <cyd@stupidchicken.com> writes:

  > Stefan Monnier <monnier@iro.umontreal.ca> writes:
  > 
  > >> I thought only relatively minor and safe ones,
  > >> but this one seems to break that rule, at least in my book.
  > >
  > > It looks pretty safe: the first step is to add the Lisp API, which
  > > should not impact any other code (tho it may cause temporary build
  > > failures, I guess).  After that, set-auto-mode (and/or image.el, ...)
  > > will need to be tweaked to also take libmagic into account
  > > when available.  This should also be fairly simple.
  > 
  > I don't think that sounds simple or safe; however, there's not enough
  > information to know for sure, until Joakim posts the patch.
  > 
  > >> Maybe we should simply decide right here and now that Emacs 23.2 will
  > >> be delivered from the RC branch, and open the trunk for all changes,
  > >> even not-so-safe ones?
  > >
  > > Yes, that's pretty much where we're at, I think, yes.
  > 
  > Actually, if people want to start including more intrusive changes, I
  > think we should cut a new branch from the current trunk.

Are there any plans for the next release?

IMO we need to make a bug fix release ASAP, this bug:

http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=4146

warrants it.  

Not being able to set the C style in a file (or directory) local
variable is a major annoyance for users.

Re: next bugfix release?

[Chong Yidong]

Dan Nicolaescu <dann@ics.uci.edu> writes:

> Are there any plans for the next release?

The plan (and Stefan agrees) is to spend about the same amount of time
as we did between 22.1 and 22.2.  This would put 23.2 around April next
year.

> IMO we need to make a bug fix release ASAP, this bug:
>
> http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=4146
>
> warrants it.  Not being able to set the C style in a file (or
> directory) local variable is a major annoyance for users.

This bug is pretty serious.  Happily, it only affects the trunk; the
23.1 release is unaffected.

The most likely culprit is the 2009-07-18 change to cc-mode.el, which we
did not apply to the release branch.

Re: next bugfix release?

[Dan Nicolaescu]

Chong Yidong <cyd@stupidchicken.com> writes:

  > Dan Nicolaescu <dann@ics.uci.edu> writes:
  > 
  > > IMO we need to make a bug fix release ASAP, this bug:
  > >
  > > http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=4146
  > >
  > > warrants it.  Not being able to set the C style in a file (or
  > > directory) local variable is a major annoyance for users.
  > 
  > This bug is pretty serious.  Happily, it only affects the trunk; the
  > 23.1 release is unaffected.

Good to hear that! (I don't have a 23.1 handy, just the CVS build...) I'll
make a note of this in the bug.

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 834 bytes --]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:
>
> I think it's a good idea.  It may require some non-trivial changes on
> the Lisp side, since libmagic's information is not quite the same as
> what Emacs currently uses: we'll probably want to use libmagic to get
> a MIME-type and then have a table mapping mime-types to major modes or
> some such.
>
>
>         Stefan

I attach an early draft filemagic patch.

Some notes:

- The mime type info usualy is less granular than the free
text info:

file --mime /tmp/tst.xcf
/tmp/tst.xcf: application/octet-stream; charset=binary

file /tmp/tst.xcf
/tmp/tst.xcf: GIMP XCF image data, version 0, 640 x 480, RGB Color

This is dependent on the file magic info file used.

- We can probably have much fun debating what the interface should look
  like at the lisp level. Any ideas? 

  

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic1.patch --]
[-- Type: text/x-patch, Size: 5605 bytes --]

diff --git a/configure.in b/configure.in
index f4096db..cb74523 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([filemagic],[don't compile with filemagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_filemagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 425cf98..b80255a 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -511,6 +512,12 @@ MSDOS_OBJ = dosfns.o msdos.o w16select.o xmenu.o
 #endif
 #endif
 
+#ifdef HAVE_LIBMAGIC
+FILEMAGIC_OBJ = filemagic.o
+#else
+FILEMAGIC_OBJ =
+#endif
+
 #ifdef CYGWIN
 CYGWIN_OBJ = sheap.o
 #endif
@@ -551,7 +558,7 @@ obj=    dispnew.o frame.o scroll.o xdisp.o menu.o $(XMENU_OBJ) window.o \
 	syntax.o UNEXEC bytecode.o \
 	process.o callproc.o \
 	region-cache.o sound.o atimer.o \
-	doprnt.o strftime.o intervals.o textprop.o composite.o md5.o \
+	doprnt.o strftime.o intervals.o textprop.o composite.o md5.o ${FILEMAGIC_OBJ} \
 	$(MSDOS_OBJ) $(NS_OBJ) $(CYGWIN_OBJ) $(FONT_DRIVERS)
 
 /* Object files used on some machine or other.
@@ -878,7 +885,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/config.in b/src/config.in
index 404e00b..c966a09 100644
--- a/src/config.in
+++ b/src/config.in
@@ -262,6 +262,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 /* Define to 1 if you have the gpm library (-lgpm). */
 #undef HAVE_GPM
 
+/* Define to 1 if you have the filemagic library (-lmagic). */
+#undef HAVE_LIBMAGIC
+
 /* Define to 1 if you have the `grantpt' function. */
 #undef HAVE_GRANTPT
 
diff --git a/src/emacs.c b/src/emacs.c
index 657465d..03d7744 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -1683,6 +1683,9 @@ main (int argc, char **argv)
       syms_of_window ();
       syms_of_xdisp ();
       syms_of_font ();
+#ifdef HAVE_LIBMAGIC
+      syms_of_filemagic();
+#endif
 #ifdef HAVE_WINDOW_SYSTEM
       syms_of_fringe ();
       syms_of_image ();
diff --git a/src/filemagic.c b/src/filemagic.c
new file mode 100644
index 0000000..1dcf065
--- /dev/null
+++ b/src/filemagic.c
@@ -0,0 +1,65 @@
+#include <magic.h>
+#include <config.h>
+#include <stdio.h>
+#include <math.h>
+#include <ctype.h>
+
+#include "lisp.h"
+/*
+
+ */
+/*
+     magic_t
+     magic_open(int flags);
+
+     void
+     magic_close(magic_t cookie);
+
+     const char *
+     magic_error(magic_t cookie);
+
+     int
+     magic_errno(magic_t cookie);
+
+     const char *
+     magic_file(magic_t cookie, const char *filename);
+
+     const char *
+     magic_buffer(magic_t cookie, const void *buffer, size_t length);
+
+     int
+     magic_setflags(magic_t cookie, int flags);
+
+     int
+     magic_check(magic_t cookie, const char *filename);
+
+     int
+     magic_compile(magic_t cookie, const char *filename);
+
+     int
+     magic_load(magic_t cookie, const char *filename);
+*/
+
+
+DEFUN ("file-magic-file", Ffile_magic_file, Sfile_magic_file, 1,1,0,
+       doc: /* return libmagic file description for filename */)
+  (filename)
+     Lisp_Object filename;
+{
+  if (!STRINGP (filename)) return Qnil;
+  printf("filename:%s\n",SDATA(filename));
+  magic_t cookie= magic_open(MAGIC_MIME_TYPE);
+  magic_load(cookie,NULL);
+  printf("cookie:%d\n",cookie);
+  char *rvs=magic_file(cookie, SDATA(filename));
+  printf("rvs:%s\n",rvs);  
+  Lisp_Object rv=intern(rvs);
+  magic_close(cookie);
+  return rv;
+}
+
+void
+syms_of_filemagic ()
+{
+  defsubr (&Sfile_magic_file);
+}

[-- Attachment #3: Type: text/plain, Size: 20 bytes --]



-- 
Joakim Verona

Re: next bugfix release?

[Alan Mackenzie]

Hi, Everybody!

On Wed, Aug 19, 2009 at 05:06:29PM -0400, Chong Yidong wrote:
> Dan Nicolaescu <dann@ics.uci.edu> writes:

> > Are there any plans for the next release?

> The plan (and Stefan agrees) is to spend about the same amount of time
> as we did between 22.1 and 22.2.  This would put 23.2 around April next
> year.

> > IMO we need to make a bug fix release ASAP, this bug:

> > http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=4146

> > warrants it.  Not being able to set the C style in a file (or
> > directory) local variable is a major annoyance for users.

OK.  This is for me to fix, so I'm acknowledging having seen it.

> This bug is pretty serious.  Happily, it only affects the trunk; the
> 23.1 release is unaffected.

Phew!  Thanks for that!

> The most likely culprit is the 2009-07-18 change to cc-mode.el, which
> we did not apply to the release branch.

Yes.  It's one of these @dfn{wallpaper paste} bugs, where when you press
an area of wallpaper firmly to the wall, the paste under it pops up
another bit of wallpaper somewhere else.  It's going to be a horrible bug
to fix.  Indeed, it may not be fixable, in the sense of doing the Right
Thing under every reasonable circumstance.

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: next bugfix release?

[Nick Roberts]

 > Yes.  It's one of these @dfn{wallpaper paste} bugs, where when you press
 > an area of wallpaper firmly to the wall, the paste under it pops up
 > another bit of wallpaper somewhere else.  It's going to be a horrible bug
 > to fix.  Indeed, it may not be fixable, in the sense of doing the Right
 > Thing under every reasonable circumstance.

Such 'bubbles', usually called regressions, might be less likely to appear
if, as Cyd suggested, there was a CC mode equivalent of compilation.txt.
I can't find this post now, so apologies if it reached a logical conclusion.
It might also be harder to implement than compilation.txt, as expressions
are probably not as self contained, but some kind of testuite seems essential
to prevent these issues from recurring.

-- 
Nick                                           http://www.inet.net.nz/~nickrob

Re: using libmagic in Emacs?

[Dan Nicolaescu]

joakim@verona.se writes:

  > Stefan Monnier <monnier@IRO.UMontreal.CA> writes:
  > >
  > > I think it's a good idea.  It may require some non-trivial changes on
  > > the Lisp side, since libmagic's information is not quite the same as
  > > what Emacs currently uses: we'll probably want to use libmagic to get
  > > a MIME-type and then have a table mapping mime-types to major modes or
  > > some such.
  > >
  > >
  > >         Stefan
  > 
  > I attach an early draft filemagic patch.
  > 
  > Some notes:
  > 
  > - The mime type info usualy is less granular than the free
  > text info:
  > 
  > file --mime /tmp/tst.xcf
  > /tmp/tst.xcf: application/octet-stream; charset=binary
  > 
  > file /tmp/tst.xcf
  > /tmp/tst.xcf: GIMP XCF image data, version 0, 640 x 480, RGB Color
  > 
  > This is dependent on the file magic info file used.
  > 
  > - We can probably have much fun debating what the interface should look
  >   like at the lisp level. Any ideas? 
  > 
  >   diff --git a/configure.in b/configure.in
  > index f4096db..cb74523 100644
  > --- a/configure.in
  > +++ b/configure.in
  > @@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
  >  OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
  >  OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
  >  
  > +OPTION_DEFAULT_ON([filemagic],[don't compile with filemagic support])
  > +
  >  OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
  >  OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
  >  OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
  > @@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
  >     AC_MSG_ERROR( [a system implementation of alloca is required] )
  >  fi
  >  
  > +
  > +HAVE_LIBMAGIC=no
  > +if test "${with_filemagic}" != "no"; then
  > +  #libmagic support
  > +  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
  > +fi
  > +
  > +if test "${HAVE_LIBMAGIC}" = "yes"; then
  > +  LIBMAGIC=-lmagic
  > +  AC_SUBST(LIBMAGIC)
  > +  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
  > +fi
  > +
  >  # fmod, logb, and frexp are found in -lm on most systems.
  >  # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
  >  AC_CHECK_LIB(m, sqrt)
  > @@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
  >  echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
  >  echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
  >  echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
  > +echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
  >  
  >  echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
  >  echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
  > diff --git a/src/Makefile.in b/src/Makefile.in
  > index 425cf98..b80255a 100644
  > --- a/src/Makefile.in
  > +++ b/src/Makefile.in
  > @@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
  >  #endif /* not HAVE_LIBRESOLV */
  >  
  >  LIBSOUND= @LIBSOUND@
  > +LIBMAGIC= @LIBMAGIC@
  >  CFLAGS_SOUND= @CFLAGS_SOUND@
  >  
  >  RSVG_LIBS= @RSVG_LIBS@
  > @@ -511,6 +512,12 @@ MSDOS_OBJ = dosfns.o msdos.o w16select.o xmenu.o
  >  #endif
  >  #endif
  >  
  > +#ifdef HAVE_LIBMAGIC
  > +FILEMAGIC_OBJ = filemagic.o
  > +#else
  > +FILEMAGIC_OBJ =
  > +#endif

Can you please avoid adding new #ifdefs here? (we are trying to get rid
of them).
Maybe use @FILEMAGIC_OBJ@ ?

Or even use the file unconditionally, just add the proper #ifdefs to
make it be empty if not HAVE_LIBMAGIC ?

Re: using libmagic in Emacs?

[Stephen J. Turnbull]

joakim@verona.se writes:

 > - We can probably have much fun debating what the interface should look
 >   like at the lisp level. Any ideas? 

I think the main interface should be just "file-magic", even if it's
not in file.el.  It's analogous to "file-attributes", etc.
"file-magic-file" sounds like it returns the magic file (file*s*
possible?) used.

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: "Stephen J. Turnbull" <stephen@xemacs.org>
> Date: Thu, 20 Aug 2009 10:03:24 +0900
> Cc: Stefan Monnier <monnier@IRO.UMontreal.CA>,
> 	Emacs Development <emacs-devel@gnu.org>
> 
> joakim@verona.se writes:
> 
>  > - We can probably have much fun debating what the interface should look
>  >   like at the lisp level. Any ideas? 
> 
> I think the main interface should be just "file-magic", even if it's
> not in file.el.  It's analogous to "file-attributes", etc.

Actually, I think the interface should be `file-type' or some such.
Like `file-attributes' that is a wrapper for `stat', the API name
should have a good semantic value, instead of just inheriting the name
of the low-level C functions it uses to do the job.

Re: using libmagic in Emacs?

[Richard Stallman]

    >> For instance, in "image.el" there is functionality to look at magic
    >> numbers in image files.

    image.el doesn't recognize some rare JPEG formats, so libmagic will be
    useful here.

Extending image.el mightbe a lot easier than other solutions.

Re: using libmagic in Emacs?

[Stephen J. Turnbull]

Eli Zaretskii writes:

 > > I think the main interface should be just "file-magic", even if it's
 > > not in file.el.  It's analogous to "file-attributes", etc.
 > 
 > Actually, I think the interface should be `file-type' or some such.

Seriously, "file-type" is a terrible, ambiguous name.  DOS vs. Unix,
the extension of the file's name (!!), what program uses it, text
vs. binary, MIME type, endianness of the platform, Unicode vs. legacy
coding, copyleft vs. permissive vs. proprietary vs. public domain, I
could go on.  Sure, it's about "files", but the "type" is what file(1)
infers from magic numbers in the file, no more and no less ... and
exactly the people you expect to say "huh?" will proceed to guess
anything but the truth about the semantics of `file-type'.

 > Like `file-attributes' that is a wrapper for `stat', the API name
 > should have a good semantic value, instead of just inheriting the name
 > of the low-level C functions it uses to do the job.

`file-magic' does have a good semantic value.  It means "look at the
first few bytes of a file and infer various metadata about it, based
on a published database of 'magic numbers'."  It tells not only the
purpose but the exact semantics.

I suppose the more explicit `file-type-by-magic' might be better.

Re: next bugfix release?

[Lennart Borgman]

On Thu, Aug 20, 2009 at 1:16 AM, Nick Roberts<nickrob@snap.net.nz> wrote:
>  > Yes.  It's one of these @dfn{wallpaper paste} bugs, where when you press
>  > an area of wallpaper firmly to the wall, the paste under it pops up
>  > another bit of wallpaper somewhere else.  It's going to be a horrible bug
>  > to fix.  Indeed, it may not be fixable, in the sense of doing the Right
>  > Thing under every reasonable circumstance.
>
> Such 'bubbles', usually called regressions, might be less likely to appear
> if, as Cyd suggested, there was a CC mode equivalent of compilation.txt.
> I can't find this post now, so apologies if it reached a logical conclusion.
> It might also be harder to implement than compilation.txt, as expressions
> are probably not as self contained, but some kind of testuite seems essential
> to prevent these issues from recurring.


Is not some kind of unit tests what we want here?

Adding a unit test for at least every serious and difficult bug seems
to me the right thing to do.


There are some unit tests frameworks on EmacsWiki. I have one modified
version of one of these in nXhtml. And CEDET has some unit tests
(which I have not looked at but I have run the test suite).

Re: next bugfix release?

[Eric M. Ludlam]

On Thu, 2009-08-20 at 11:02 +0200, Lennart Borgman wrote:
> On Thu, Aug 20, 2009 at 1:16 AM, Nick Roberts<nickrob@snap.net.nz> wrote:
> >  > Yes.  It's one of these @dfn{wallpaper paste} bugs, where when you press
> >  > an area of wallpaper firmly to the wall, the paste under it pops up
> >  > another bit of wallpaper somewhere else.  It's going to be a horrible bug
> >  > to fix.  Indeed, it may not be fixable, in the sense of doing the Right
> >  > Thing under every reasonable circumstance.
> >
> > Such 'bubbles', usually called regressions, might be less likely to appear
> > if, as Cyd suggested, there was a CC mode equivalent of compilation.txt.
> > I can't find this post now, so apologies if it reached a logical conclusion.
> > It might also be harder to implement than compilation.txt, as expressions
> > are probably not as self contained, but some kind of testuite seems essential
> > to prevent these issues from recurring.
> 
> 
> Is not some kind of unit tests what we want here?
> 
> Adding a unit test for at least every serious and difficult bug seems
> to me the right thing to do.
> 
> 
> There are some unit tests frameworks on EmacsWiki. I have one modified
> version of one of these in nXhtml. And CEDET has some unit tests
> (which I have not looked at but I have run the test suite).

Just as another vote for testing, CEDET floundered for a long time with
performance and accuracy issues (say from 1996 through 2007 or so) until
I started adding test suites.  Ever since, I've been able to do sweeping
changes to the underpinnings for performance, bugs or new features, and
know that everything still works by running a single "make" command.
Every user reported bug I fix gets a new test in one of the pre-existing
test suites as I work on the bug, and several folks on the mailing list
now are very good at providing test snippets for me, keeping maintenance
and overhead low.

I highly recommend doing the same for any complex task in Emacs.

Eric

Re: using libmagic in Emacs?

[Stefan Monnier]

>> I think it's a good idea.  It may require some non-trivial changes on
>> the Lisp side, since libmagic's information is not quite the same as
>> what Emacs currently uses: we'll probably want to use libmagic to get
>> a MIME-type and then have a table mapping mime-types to major modes or
>> some such.

> I attach an early draft filemagic patch.

> Some notes:

> - The mime type info usualy is less granular than the free
> text info:

We can provide both.  I think we'd want 2 functions: one to get the free
text info, which just returns a string (or nil), and another to get the
MIME info, which returns a cons, whose car is a symbol such as
application/octet-stream, and whose cdr is an alist representing
the additional optional info.

> file --mime /tmp/tst.xcf
> /tmp/tst.xcf: application/octet-stream; charset=binary

This would look like (application/octet-stream (charset . "binary"))

A few more comments:
- please follow the GNU coding convention.  I.e. put spaces where
  they need to be (e.g. around parens and operators).
- don't bother with a new file.  Just put it into fileio.c.
- as someone else mentioned, CPP macros in the Makefile.in are things
  we'd like to get rid of, so please don't put more of them there.
  Use autoconf's m4 macros instead, thank you.


        Stefan

Re: next bugfix release?

[Alan Mackenzie]

Hi, Nick,

On Thu, Aug 20, 2009 at 11:16:18AM +1200, Nick Roberts wrote:
>  > Yes.  It's one of these @dfn{wallpaper paste} bugs, where when you
>  > press an area of wallpaper firmly to the wall, the paste under it
>  > pops up another bit of wallpaper somewhere else.  It's going to be
>  > a horrible bug to fix.  Indeed, it may not be fixable, in the sense
>  > of doing the Right Thing under every reasonable circumstance.

> Such 'bubbles', usually called regressions, ....

No, that's not what I meant (although it is also a regression).  I was
talking about the high complexity caused by the number of things that
all have to work right at the same time.  The "fix" I made to cc-mode.el
in July fixed one problem but created another.  Getting them all working
simultaneously is going to be hard.

This complexity has increased recently due to the new feature "directory
locals".  I didn't become aware of this when it was introduced (my bad),
and the person who wrote it wasn't aware of the trouble it would cause
CC Mode (why should he be?).

The trouble is, there are too many ways of setting a CC Mode "style
variable" (such as c-basic-offset), @xref{Config Basics,,, ccmode}.  It
is not always the last setting which should prevail over previous ones.
It is a complexity which nobody would design; it has emerged as such
over CC Mode's lifetime, and is now a mess.  the .dir-locals feature may
have pushed the complexity over the edge of what is manageable.

> ...., might be less likely to appear if, as Cyd suggested, there was a
> CC mode equivalent of compilation.txt.

Er, what's .../etc/compilation.txt about?  It has an alleged explanation
at the top, but that only makes sense if you already have some context.
For example, you need to know why you'd "need matchers", and what sort
of "matchers" they are.

> I can't find this post now, so apologies if it reached a logical
> conclusion.  It might also be harder to implement than
> compilation.txt, as expressions are probably not as self contained,
> but some kind of testuite seems essential to prevent these issues from
> recurring.

CC Mode has an extensive test suite for (static) indentation and
fontification.  It doesn't have any such tests for things like
initialisation of the mode, execution of CC Mode commands, or for
indentation/fontification after buffer changes.  I would very much
welcome anybody stepping forward who had the time and energy to write
these tests.

> Nick

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: next bugfix release?

[Lennart Borgman]

On Thu, Aug 20, 2009 at 5:13 PM, Alan Mackenzie<acm@muc.de> wrote:

> CC Mode has an extensive test suite for (static) indentation and
> fontification.  It doesn't have any such tests for things like
> initialisation of the mode, execution of CC Mode commands, or for
> indentation/fontification after buffer changes.  I would very much
> welcome anybody stepping forward who had the time and energy to write
> these tests.


The tests I use for nXhtml tries to emulate commands (taking into
pre/post etc) which might help for doing this. It also tries to
fontify by explicitly calling the timers. Maybe this can help. If
someone wants to try I can explain more.

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: "Stephen J. Turnbull" <stephen@xemacs.org>
> Cc: monnier@IRO.UMontreal.CA,
>     joakim@verona.se,
>     emacs-devel@gnu.org
> Date: Thu, 20 Aug 2009 13:50:13 +0900
> 
> Eli Zaretskii writes:
> 
>  > > I think the main interface should be just "file-magic", even if it's
>  > > not in file.el.  It's analogous to "file-attributes", etc.
>  > 
>  > Actually, I think the interface should be `file-type' or some such.
> 
> Seriously, "file-type" is a terrible, ambiguous name.  DOS vs. Unix,
> the extension of the file's name (!!), what program uses it, text
> vs. binary, MIME type, endianness of the platform, Unicode vs. legacy
> coding, copyleft vs. permissive vs. proprietary vs. public domain, I
> could go on.  Sure, it's about "files", but the "type" is what file(1)
> infers from magic numbers in the file, no more and no less ... and
> exactly the people you expect to say "huh?" will proceed to guess
> anything but the truth about the semantics of `file-type'.

Maybe so, but still "man file" shows this at the very first line:

       file - determine file type

> I suppose the more explicit `file-type-by-magic' might be better.

I'm okay with that as well, but maybe `file-type-by-magic-signature'
is even better (if we indeed want to advertise its inner workings).
But if this function will fall back on something else if libmagic is
not available, then I think this name is not a good one.

Re: using libmagic in Emacs?

[Richard Stallman]

    Actually, I think the interface should be `file-type' or some such.

If it will return the MIME type, `file-mime-type' seems like a good
name.

Re: using libmagic in Emacs?

[Richard Stallman]

If we go this route, we should not load gnus/mailcap.el.
It contains lots of other stuff.  So we ought to separate
out and preload the right part of it, such as the variable
`mailcap-mime-data'.

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 1693 bytes --]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>> I think it's a good idea.  It may require some non-trivial changes on
>>> the Lisp side, since libmagic's information is not quite the same as
>>> what Emacs currently uses: we'll probably want to use libmagic to get
>>> a MIME-type and then have a table mapping mime-types to major modes or
>>> some such.
>
>> I attach an early draft filemagic patch.
>
>> Some notes:
>
>> - The mime type info usualy is less granular than the free
>> text info:
>
> We can provide both.  I think we'd want 2 functions: one to get the free
> text info, which just returns a string (or nil), and another to get the
> MIME info, which returns a cons, whose car is a symbol such as
> application/octet-stream, and whose cdr is an alist representing
> the additional optional info.
>
>> file --mime /tmp/tst.xcf
>> /tmp/tst.xcf: application/octet-stream; charset=binary
>
> This would look like (application/octet-stream (charset . "binary"))
>
> A few more comments:
> - please follow the GNU coding convention.  I.e. put spaces where
>   they need to be (e.g. around parens and operators).
> - don't bother with a new file.  Just put it into fileio.c.
> - as someone else mentioned, CPP macros in the Makefile.in are things
>   we'd like to get rid of, so please don't put more of them there.
>   Use autoconf's m4 macros instead, thank you.
>
>
>         Stefan

Find attached a new slightly improved patch according to the suggestions
of the list.

However, I see now I didnt properly read your text above, the
function I wrote now returns a list with 3 elements, (MIME_TYPE
MIME_ENCODING DESCRIPTION). Do we still need 2 functions as you write
above?


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic2.patch --]
[-- Type: text/x-patch, Size: 5232 bytes --]

diff --git a/configure.in b/configure.in
index f4096db..cb74523 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([filemagic],[don't compile with filemagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_filemagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 425cf98..33d1a14 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -878,7 +879,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/config.in b/src/config.in
index 404e00b..c966a09 100644
--- a/src/config.in
+++ b/src/config.in
@@ -262,6 +262,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 /* Define to 1 if you have the gpm library (-lgpm). */
 #undef HAVE_GPM
 
+/* Define to 1 if you have the filemagic library (-lmagic). */
+#undef HAVE_LIBMAGIC
+
 /* Define to 1 if you have the `grantpt' function. */
 #undef HAVE_GRANTPT
 
diff --git a/src/fileio.c b/src/fileio.c
index 3702d4c..375502e 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
 int write_region_inhibit_fsync;
 #endif
 
+#ifdef HAVE_LIBMAGIC
+#include <magic.h>
+#endif
+
 /* Non-zero means call move-file-to-trash in Fdelete_file or
    Fdelete_directory.  */
 int delete_by_moving_to_trash;
@@ -2997,6 +3001,45 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
 
 #endif /* HAVE_SYNC */
 
+#ifdef HAVE_LIBMAGIC
+DEFUN ("file-magic-file", Ffile_magic_file, Sfile_magic_file, 1,1,0,
+       doc: /* Return (MIME_TYPE MIME_ENCODING DESCRIPTION) for FILENAME.
+Return nil on error. */)
+  (filename)
+     Lisp_Object filename;
+{
+  magic_t cookie=NULL;
+  if (!STRINGP (filename)) goto libmagic_error;
+  char* f = SDATA (filename);
+  char* rvs;
+  cookie = magic_open (MAGIC_NONE);
+  magic_load (cookie,NULL); //load default database
+
+  magic_setflags (cookie, MAGIC_MIME_TYPE);  
+  rvs = magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  Lisp_Object file_mime = intern (rvs);
+
+  magic_setflags (cookie, MAGIC_MIME_ENCODING);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  Lisp_Object file_encoding = intern(rvs);  
+
+  magic_setflags (cookie, MAGIC_NONE);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+
+  Lisp_Object file_freetext = make_specified_string (rvs, strlen(rvs), strlen(rvs), NULL);    
+  Lisp_Object rv = Fcons (file_mime, Fcons (file_encoding, Fcons (file_freetext, Qnil)));
+  
+  magic_close (cookie);
+  return rv;
+ libmagic_error:
+  if (cookie != NULL) magic_close (cookie);  
+  return Qnil;
+}
+#endif
+
 DEFUN ("file-newer-than-file-p", Ffile_newer_than_file_p, Sfile_newer_than_file_p, 2, 2, 0,
        doc: /* Return t if file FILE1 is newer than file FILE2.
 If FILE1 does not exist, the answer is nil;
@@ -5781,6 +5824,9 @@ When non-nil, the function `move-file-to-trash' will be used by
 #ifdef HAVE_SYNC
   defsubr (&Sunix_sync);
 #endif
+#ifdef HAVE_LIBMAGIC
+    defsubr (&Sfile_magic_file);
+#endif
 }
 
 /* arch-tag: 64ba3fd7-f844-4fb2-ba4b-427eb928786c

[-- Attachment #3: Type: text/plain, Size: 20 bytes --]



-- 
Joakim Verona

Re: using libmagic in Emacs?

[Reiner Steib]

On Thu, Aug 20 2009, Richard Stallman wrote:

> If we go this route, we should not load gnus/mailcap.el.

(mailcap.el doesn't load anything else, AFAICS.)

> It contains lots of other stuff.  

Ironically last year some stuff from dired-aux.el was moved to
mailcap.el and is used in `minibuffer-default-add-shell-commands' from
simple.el.

> So we ought to separate out and preload the right part of it, such
> as the variable `mailcap-mime-data'.

The initial value of `mailcap-mime-data' is a fall-back (for systems
without proper mailcap files).  To make it useful, probably
`mailcap-parse-mailcaps' and related functions are necessary:

$ emacs-23-1 -Q -f ielm -l mailcap
...
ELISP> (with-temp-buffer
	 (insert
	  (pp-to-string mailcap-mime-data))
	 (point-max))
4993
ELISP> (mailcap-parse-mailcaps)
t
ELISP> (with-temp-buffer
	 (insert
	  (pp-to-string mailcap-mime-data))
	 (point-max))
40322
ELISP> system-type
gnu/linux

Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/

Re: using libmagic in Emacs?

[Andreas Schwab]

joakim@verona.se writes:

> diff --git a/configure.in b/configure.in
> index f4096db..cb74523 100644
> --- a/configure.in
> +++ b/configure.in
> @@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
>  OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
>  OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
>  
> +OPTION_DEFAULT_ON([filemagic],[don't compile with filemagic support])

IMHO the option should be named libmagic, since that's how the library
is named.

> diff --git a/src/config.in b/src/config.in
> index 404e00b..c966a09 100644
> --- a/src/config.in
> +++ b/src/config.in
> @@ -262,6 +262,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
>  /* Define to 1 if you have the gpm library (-lgpm). */
>  #undef HAVE_GPM
>  
> +/* Define to 1 if you have the filemagic library (-lmagic). */
> +#undef HAVE_LIBMAGIC
> +
>  /* Define to 1 if you have the `grantpt' function. */
>  #undef HAVE_GRANTPT
>  

This is generated by autoheader.

> diff --git a/src/fileio.c b/src/fileio.c
> index 3702d4c..375502e 100644
> --- a/src/fileio.c
> +++ b/src/fileio.c
> @@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
>  int write_region_inhibit_fsync;
>  #endif
>  
> +#ifdef HAVE_LIBMAGIC
> +#include <magic.h>
> +#endif
> +
>  /* Non-zero means call move-file-to-trash in Fdelete_file or
>     Fdelete_directory.  */
>  int delete_by_moving_to_trash;
> @@ -2997,6 +3001,45 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
>  
>  #endif /* HAVE_SYNC */
>  
> +#ifdef HAVE_LIBMAGIC
> +DEFUN ("file-magic-file", Ffile_magic_file, Sfile_magic_file, 1,1,0,
> +       doc: /* Return (MIME_TYPE MIME_ENCODING DESCRIPTION) for FILENAME.
> +Return nil on error. */)
> +  (filename)
> +     Lisp_Object filename;
> +{
> +  magic_t cookie=NULL;
> +  if (!STRINGP (filename)) goto libmagic_error;

Just use CHECK_STRING.

> +  char* f = SDATA (filename);
> +  char* rvs;

No C99 features yet.  Be careful with raw string pointers and GC.

> +  cookie = magic_open (MAGIC_NONE);
> +  magic_load (cookie,NULL); //load default database

if (cookie == NULL) ?

> +
> +  magic_setflags (cookie, MAGIC_MIME_TYPE);  
> +  rvs = magic_file (cookie, f);
> +  if (rvs == NULL) goto libmagic_error;

Use report_file_error, provided that magic_file sets errno appropriately.

> +  Lisp_Object file_freetext = make_specified_string (rvs, strlen(rvs), strlen(rvs), NULL);    

Use build_string.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: using libmagic in Emacs?

[Stephen J. Turnbull]

Eli Zaretskii writes:

 > Maybe so, but still "man file" shows this at the very first line:
 > 
 >        file - determine file type

Sure.  file does more than invoke libmagic, though, and in the Unix
context the ambiguous "type" is not so problematic; it is basically
defined by "what file(1) does."  For the broader audience, if "magic"
is unacceptable, they probably don't know what file(1) does.

 > But if this function will fall back on something else if libmagic is
 > not available, then I think this name is not a good one.

This function should be available in a form which only uses libmagic.
What other tests should be done should be done in LISP, and I see no
reason to hide the libmagic functionality in an "-internal" or
otherwise "not for regular use" form.

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 2964 bytes --]

New libmagic patch, mostly fixing Andreas concerns, and some more error
handling.

I dont understand the autoheader comment below though. When I originaly
compiled, the config.h wasnt generated with the libmagic info included,
did I do something wrong? Is autoheader supposed to generate config.in?
When does that happen?

/Joakim

Andreas Schwab <schwab@linux-m68k.org> writes:

> joakim@verona.se writes:
>
>> diff --git a/configure.in b/configure.in
>> index f4096db..cb74523 100644
>> --- a/configure.in
>> +++ b/configure.in
>> @@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
>>  OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
>>  OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
>>  
>> +OPTION_DEFAULT_ON([filemagic],[don't compile with filemagic support])
>
> IMHO the option should be named libmagic, since that's how the library
> is named.
>
>> diff --git a/src/config.in b/src/config.in
>> index 404e00b..c966a09 100644
>> --- a/src/config.in
>> +++ b/src/config.in
>> @@ -262,6 +262,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
>>  /* Define to 1 if you have the gpm library (-lgpm). */
>>  #undef HAVE_GPM
>>  
>> +/* Define to 1 if you have the filemagic library (-lmagic). */
>> +#undef HAVE_LIBMAGIC
>> +
>>  /* Define to 1 if you have the `grantpt' function. */
>>  #undef HAVE_GRANTPT
>>  
>
> This is generated by autoheader.
>
>> diff --git a/src/fileio.c b/src/fileio.c
>> index 3702d4c..375502e 100644
>> --- a/src/fileio.c
>> +++ b/src/fileio.c
>> @@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
>>  int write_region_inhibit_fsync;
>>  #endif
>>  
>> +#ifdef HAVE_LIBMAGIC
>> +#include <magic.h>
>> +#endif
>> +
>>  /* Non-zero means call move-file-to-trash in Fdelete_file or
>>     Fdelete_directory.  */
>>  int delete_by_moving_to_trash;
>> @@ -2997,6 +3001,45 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
>>  
>>  #endif /* HAVE_SYNC */
>>  
>> +#ifdef HAVE_LIBMAGIC
>> +DEFUN ("file-magic-file", Ffile_magic_file, Sfile_magic_file, 1,1,0,
>> +       doc: /* Return (MIME_TYPE MIME_ENCODING DESCRIPTION) for FILENAME.
>> +Return nil on error. */)
>> +  (filename)
>> +     Lisp_Object filename;
>> +{
>> +  magic_t cookie=NULL;
>> +  if (!STRINGP (filename)) goto libmagic_error;
>
> Just use CHECK_STRING.
>
>> +  char* f = SDATA (filename);
>> +  char* rvs;
>
> No C99 features yet.  Be careful with raw string pointers and GC.
>
>> +  cookie = magic_open (MAGIC_NONE);
>> +  magic_load (cookie,NULL); //load default database
>
> if (cookie == NULL) ?
>
>> +
>> +  magic_setflags (cookie, MAGIC_MIME_TYPE);  
>> +  rvs = magic_file (cookie, f);
>> +  if (rvs == NULL) goto libmagic_error;
>
> Use report_file_error, provided that magic_file sets errno appropriately.
>
>> +  Lisp_Object file_freetext = make_specified_string (rvs, strlen(rvs), strlen(rvs), NULL);    
>
> Use build_string.
>
> Andreas.

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic3.patch --]
[-- Type: text/x-patch, Size: 5540 bytes --]

diff --git a/configure.in b/configure.in
index f4096db..49a3f15 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([libmagic],[don't compile with libmagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_libmagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 425cf98..33d1a14 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -878,7 +879,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/config.in b/src/config.in
index 404e00b..c966a09 100644
--- a/src/config.in
+++ b/src/config.in
@@ -262,6 +262,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 /* Define to 1 if you have the gpm library (-lgpm). */
 #undef HAVE_GPM
 
+/* Define to 1 if you have the filemagic library (-lmagic). */
+#undef HAVE_LIBMAGIC
+
 /* Define to 1 if you have the `grantpt' function. */
 #undef HAVE_GRANTPT
 
diff --git a/src/fileio.c b/src/fileio.c
index 3702d4c..67d271c 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
 int write_region_inhibit_fsync;
 #endif
 
+#ifdef HAVE_LIBMAGIC
+#include <magic.h>
+#endif
+
 /* Non-zero means call move-file-to-trash in Fdelete_file or
    Fdelete_directory.  */
 int delete_by_moving_to_trash;
@@ -2997,6 +3001,52 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
 
 #endif /* HAVE_SYNC */
 
+#ifdef HAVE_LIBMAGIC
+DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
+       doc: /* Return (MIME_TYPE MIME_ENCODING DESCRIPTION) for FILENAME_OR_BUFFER.
+Return nil on error. */)
+  (filename_or_buffer)
+     Lisp_Object filename_or_buffer;
+{
+  CHECK_STRING_OR_BUFFER (filename_or_buffer);
+  magic_t cookie=NULL;
+  char* f = NULL;
+  const char* rvs;
+
+  if (STRINGP (filename_or_buffer))
+    f = SDATA (filename_or_buffer);
+  if (BUFFERP (filename_or_buffer))
+    f = SDATA (XBUFFER (filename_or_buffer)->filename);
+  cookie = magic_open (MAGIC_ERROR);
+  if (cookie == NULL) goto libmagic_error;  
+  magic_load (cookie, NULL); //load default database
+
+  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
+  rvs = magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  Lisp_Object file_mime = intern (rvs);
+
+  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  Lisp_Object file_encoding = intern(rvs);  
+
+  magic_setflags (cookie, MAGIC_NONE | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+
+  Lisp_Object file_freetext = build_string (rvs);
+  Lisp_Object rv = Fcons (file_mime, Fcons (file_encoding, Fcons (file_freetext, Qnil)));
+  
+  magic_close (cookie);
+  return rv;
+ libmagic_error:
+  if (cookie != NULL) magic_close (cookie);  
+  report_file_error("Libmagic error",Qnil);
+  return Qnil;
+}
+#endif
+
 DEFUN ("file-newer-than-file-p", Ffile_newer_than_file_p, Sfile_newer_than_file_p, 2, 2, 0,
        doc: /* Return t if file FILE1 is newer than file FILE2.
 If FILE1 does not exist, the answer is nil;
@@ -5781,6 +5831,9 @@ When non-nil, the function `move-file-to-trash' will be used by
 #ifdef HAVE_SYNC
   defsubr (&Sunix_sync);
 #endif
+#ifdef HAVE_LIBMAGIC
+    defsubr (&Slibmagic_file_internal);
+#endif
 }
 
 /* arch-tag: 64ba3fd7-f844-4fb2-ba4b-427eb928786c

[-- Attachment #3: Type: text/plain, Size: 19 bytes --]


-- 
Joakim Verona

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: joakim@verona.se
> Date: Fri, 21 Aug 2009 11:55:45 +0200
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>,
> 	Emacs Development <emacs-devel@gnu.org>
> 
> Is autoheader supposed to generate config.in?

Yes.

> When does that happen?

Either run autoheader by hand, or run autoreconf (which AFAIK is
supposed to run autoheader as well).

> +DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
> +       doc: /* Return (MIME_TYPE MIME_ENCODING DESCRIPTION) for FILENAME_OR_BUFFER.
> +Return nil on error. */)

This doc string "needs work"(TM).  Please use the doc string of
visited-file-name as an example.

> +  (filename_or_buffer)
> +     Lisp_Object filename_or_buffer;

Using a `_' in an argument is un-Lisp'y (IMO).

> +{
> +  CHECK_STRING_OR_BUFFER (filename_or_buffer);
> +  magic_t cookie=NULL;
> +  char* f = NULL;
> +  const char* rvs;
> +
> +  if (STRINGP (filename_or_buffer))
> +    f = SDATA (filename_or_buffer);
> +  if (BUFFERP (filename_or_buffer))
> +    f = SDATA (XBUFFER (filename_or_buffer)->filename);
> +  cookie = magic_open (MAGIC_ERROR);
> +  if (cookie == NULL) goto libmagic_error;  
> +  magic_load (cookie, NULL); //load default database
> +
> +  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
> +  rvs = magic_file (cookie, f);

You need to encode file names before you pass them to C APIs.  Use
ENCODE_FILE to do that; see file-attributes for an example of how this
is done.

> +  if (rvs == NULL) goto libmagic_error;
> +  Lisp_Object file_mime = intern (rvs);

You cannot declare variables in the middle of a block: Emacs does not
require a C99 compiler yet and need to support C90 or even older
compilers, which will reject this code.

> +  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
> +  rvs=magic_file (cookie, f);
> +  if (rvs == NULL) goto libmagic_error;
> +  Lisp_Object file_encoding = intern(rvs);  

Is file_encoding supposed to be a valid encoding, one of those for
which Emacs has a coding-system?  If so, perhaps you should make sure
you indeed return a valid coding-system or its alias, or otherwise
tell in the doc string that it's not guaranteed to be valid (so that
the caller should validate it before using).

Re: using libmagic in Emacs?

[Andreas Schwab]

joakim@verona.se writes:

> I dont understand the autoheader comment below though. When I originaly
> compiled, the config.h wasnt generated with the libmagic info included,
> did I do something wrong? Is autoheader supposed to generate config.in?
> When does that happen?

Configure with --enable-maintainer-mode.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: using libmagic in Emacs?

[Richard Stallman]

    The initial value of `mailcap-mime-data' is a fall-back (for systems
    without proper mailcap files).  To make it useful, probably
    `mailcap-parse-mailcaps' and related functions are necessary:

There is no need for all that to be standardly loaded/used in Emacs.

All that Emacs needs is to recognize the file types that Emacs
has special handling for.

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 1651 bytes --]

New filemagic patch mostly fixing Eli:s concerns.


Eli Zaretskii <eliz@gnu.org> writes:
>> +DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
>> +       doc: /* Return (MIME_TYPE MIME_ENCODING DESCRIPTION) for FILENAME_OR_BUFFER.
>> +Return nil on error. */)


Renamed entry point to libmagic-file-internal since its meant to be
of internal usage for a lisp wrapper, yet to be written. Should that be
a new file BTW?

> This doc string "needs work"(TM).  Please use the doc string of
> visited-file-name as an example.

I worked on this

>
>> +  (filename_or_buffer)
>> +     Lisp_Object filename_or_buffer;
>
> Using a `_' in an argument is un-Lisp'y (IMO).

Ok.

> You need to encode file names before you pass them to C APIs.  Use
> ENCODE_FILE to do that; see file-attributes for an example of how this
> is done.

Ok.

>> +  if (rvs == NULL) goto libmagic_error;
>> +  Lisp_Object file_mime = intern (rvs);
>
> You cannot declare variables in the middle of a block: Emacs does not
> require a C99 compiler yet and need to support C90 or even older
> compilers, which will reject this code.

I'm habing trouble remembering not to use c99. Is there some convenient
compiler flag to force lower versions? Fixed the errors I saw.


> Is file_encoding supposed to be a valid encoding, one of those for
> which Emacs has a coding-system?  If so, perhaps you should make sure
> you indeed return a valid coding-system or its alias, or otherwise
> tell in the doc string that it's not guaranteed to be valid (so that
> the caller should validate it before using).

I described a bit more in the doc string. Ok?



[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic3.patch --]
[-- Type: text/x-patch, Size: 5892 bytes --]

diff --git a/configure.in b/configure.in
index f4096db..49a3f15 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([libmagic],[don't compile with libmagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_libmagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 425cf98..33d1a14 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -878,7 +879,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/fileio.c b/src/fileio.c
index 3702d4c..cbb0461 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
 int write_region_inhibit_fsync;
 #endif
 
+#ifdef HAVE_LIBMAGIC
+#include <magic.h>
+#endif
+
 /* Non-zero means call move-file-to-trash in Fdelete_file or
    Fdelete_directory.  */
 int delete_by_moving_to_trash;
@@ -2997,6 +3001,77 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
 
 #endif /* HAVE_SYNC */
 
+#ifdef HAVE_LIBMAGIC
+DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
+       doc: /* Return (MIME-TYPE MIME-ENCODING DESCRIPTION) for
+FILENAME-OR-BUFFER using libmagic.  If FILENAME-OR-BUFFER is a file,
+return information about the file. If FILENAME-OR-BUFFER is a buffer,
+return information about the file of the buffer.  MIME-TYPE and
+MIME-ENCODING are the mime type and mime encoding as determined by
+libmagic.  DESCRIPTION is the human readable descripton offered by
+libmagic for the file.
+
+The default libmagic database is used, and the quality of information
+given depends on your version of that database. Often the mime type is
+less exact than the description.
+
+ */)
+  (filename_or_buffer)
+     Lisp_Object filename_or_buffer;
+{
+  CHECK_STRING_OR_BUFFER (filename_or_buffer);
+  magic_t cookie=NULL;
+  char* f = NULL;
+  const char* rvs;
+  Lisp_Object file_freetext;
+  Lisp_Object rv;
+  Lisp_Object file_mime;
+  Lisp_Object file_encoding;  
+
+  Lisp_Object filename, absname, encoded_absname;
+  struct gcpro gcpro1;
+  
+  GCPRO1 (f);
+
+  if (STRINGP (filename_or_buffer))
+    filename = filename_or_buffer;
+  if (BUFFERP (filename_or_buffer))
+    filename = XBUFFER (filename_or_buffer)->filename;
+  absname = Fexpand_file_name (filename, current_buffer->directory);
+  f = SDATA(ENCODE_FILE (absname));
+
+  cookie = magic_open (MAGIC_ERROR);
+  if (cookie == NULL) goto libmagic_error;  
+  magic_load (cookie, NULL); /* load default database */
+
+  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
+  rvs = magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  file_mime = intern (rvs);
+
+  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  file_encoding = intern(rvs);  
+
+  magic_setflags (cookie, MAGIC_NONE | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+
+  file_freetext = build_string (rvs);
+  rv = Fcons (file_mime, Fcons (file_encoding, Fcons (file_freetext, Qnil)));
+  
+  magic_close (cookie);
+  UNGCPRO;
+  return rv;
+ libmagic_error:
+  if (cookie != NULL) magic_close (cookie);  
+  report_file_error("Libmagic error",Qnil);
+  UNGCPRO;
+  return Qnil;
+}
+#endif
+
 DEFUN ("file-newer-than-file-p", Ffile_newer_than_file_p, Sfile_newer_than_file_p, 2, 2, 0,
        doc: /* Return t if file FILE1 is newer than file FILE2.
 If FILE1 does not exist, the answer is nil;
@@ -5781,6 +5856,9 @@ When non-nil, the function `move-file-to-trash' will be used by
 #ifdef HAVE_SYNC
   defsubr (&Sunix_sync);
 #endif
+#ifdef HAVE_LIBMAGIC
+    defsubr (&Slibmagic_file_internal);
+#endif
 }
 
 /* arch-tag: 64ba3fd7-f844-4fb2-ba4b-427eb928786c

[-- Attachment #3: Type: text/plain, Size: 19 bytes --]


-- 
Joakim Verona

Re: using libmagic in Emacs?

[Rupert Swarbrick]

[-- Attachment #1: Type: text/plain, Size: 393 bytes --]

joakim@verona.se writes:


> I'm habing trouble remembering not to use c99. Is there some convenient
> compiler flag to force lower versions? Fixed the errors I saw.
>

Maybe -ansi combined with -pedantic, for gcc.

  rupert@hake:~/tmp gcc -ansi -pedantic -o test test.c
  test.c: In function ‘main’:
  test.c:10: warning: ISO C90 forbids mixed declarations and code

Rupert

[-- Attachment #2: Type: application/pgp-signature, Size: 314 bytes --]

Re: using libmagic in Emacs?

[Andreas Schwab]

joakim@verona.se writes:

> +#ifdef HAVE_LIBMAGIC
> +DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
> +       doc: /* Return (MIME-TYPE MIME-ENCODING DESCRIPTION) for

The first doc line needs to be a complete sentence fitting in about 75
columns.  You should only mention the argument here, and explain the
structure of the return value in the second sentence.

> +  char* f = NULL;
> +  const char* rvs;
> +  Lisp_Object file_freetext;
> +  Lisp_Object rv;
> +  Lisp_Object file_mime;
> +  Lisp_Object file_encoding;  
> +
> +  Lisp_Object filename, absname, encoded_absname;
> +  struct gcpro gcpro1;
> +  
> +  GCPRO1 (f);

You cannot GCPRO pointers, only Lisp_Objects.

> +  if (STRINGP (filename_or_buffer))
> +    filename = filename_or_buffer;
> +  if (BUFFERP (filename_or_buffer))
> +    filename = XBUFFER (filename_or_buffer)->filename;
> +  absname = Fexpand_file_name (filename, current_buffer->directory);
> +  f = SDATA(ENCODE_FILE (absname));

Since ENCODE_FILE can GC you need to protect every Lisp_Object variable
used around the call, especially all that are Lisp_Strings.

> + libmagic_error:
> +  if (cookie != NULL) magic_close (cookie);  
> +  report_file_error("Libmagic error",Qnil);

You need to make sure that errno is preserved from the failed operation
and that you get a meaningful errno in the first place.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: joakim@verona.se
> Cc: schwab@linux-m68k.org, monnier@iro.umontreal.ca, emacs-devel@gnu.org
> Date: Fri, 21 Aug 2009 19:38:15 +0200
> 
> Renamed entry point to libmagic-file-internal since its meant to be
> of internal usage for a lisp wrapper, yet to be written. Should that be
> a new file BTW?

files.el sounds good enough to me.

> I'm habing trouble remembering not to use c99. Is there some convenient
> compiler flag to force lower versions?

I think -std=c89 should do what you want (assuming you use GCC).

> I described a bit more in the doc string. Ok?

I suggest the following variation of it:

	 doc: /* Return a list describing the argument FILE-OR-BUFFER.

  If FILE-OR-BUFFER is a file name, return information about that file.
  If FILE-OR-BUFFER is a buffer, return information about the buffer's file.

  The return value is a list of the form 

       (MIME-TYPE MIME-ENCODING DESCRIPTION)

  MIME-TYPE and MIME-ENCODING are the MIME type and encoding suitable
  for the file's contents, as determined by libmagic.
  DESCRIPTION is the human readable descripton of the file type offered by
  libmagic.

  The function throws a file-error if libmagic cannot determine one of
  the elements of the above list.

  The default libmagic database is used, and the quality of information
  given depends on your version of that database.  Often the MIME type is
  less exact than the description.  */)

Two more comments:

 . I am not sure you need to push the file-or-buffer dichotomy to the
   C level.  It is easy enough to do that in Lisp, or even in the
   application, for that matter.  Why complicate a primitive to do
   such a simple job?

 . You didn't say in the doc string whether MIME-ENCODING is
   guaranteed to be a valid Emacs coding-system.  I think a user will
   be desperate to know that.

Thanks for working on this.

Bidi support

[Stefan Monnier]

>> I was thinking of bidi for Emacs-24
> If history is of any significance, I may not live until Emacs 24.  And
> for some strange reason, the burden of adding this feature seems to be
> on my shoulders and no one else's: no development happened in this
> direction for the last several years, even though most of the
> low-level code was sitting on a branch (courtesy of Handa-san) for the
> last 4 years.

Has this branch been kept up-to-date w.r.t the trunk?
I'd guess not.  In that case, someone should do it.

I just took a look at that branch, and it doesn't look too terrible.
It made me discover the variable direction-reversed which I didn't
even know existed (and it seems that it currently has no effect :-(

> So I'd prefer it to happen sooner rather than later, at least to the
> point where the foundations are in place and others can contribute
> the rest.

Agreed.  The more I think about it, the more I think we need to open
a new branch for "what will become emacs-24".  Kind of like what we did
with the emacs-unicode branch.  I think bidi should be one of the first
features to install on that branch.

>> but if you have code ready for it
>> and if it's not too intrusive, I'd be willing to consider it.

> It is not ``ready'' in the sense that it is not yet production
> quality.  It does not yet support all the features of the Emacs
> display engine.  But it can already display bidirectional text, for
> now only in a left-to-right paragraph and only if the text has no
> faces and overlays.  The code that reorders characters for display
> isn't activated until you flip a buffer-local variable, and then only
> in that buffer.  Is that ``not too intrusive'' enough?

I think it will stay unstable for too long, so it's not good enough for
the current trunk (which I'd like to keep for shorter-term changes).


        Stefan

Re: using libmagic in Emacs?

[Stefan Monnier]

>     Actually, I think the interface should be `file-type' or some such.
> If it will return the MIME type, `file-mime-type' seems like a good
> name.

We need two functions:
- one implemented in C which provides the info from libmagic, no more no less.
- one implemented in Elisp which uses the previous one as well as
  other techniques (maybe even auto-mode-alist).

So yes, the second one can be called `file-mime-type', but the first
would better be called `file-magic' or somesuch.


        Stefan

RE: using libmagic in Emacs?

[Drew Adams]

> The first doc line needs to be a complete sentence
> fitting in about 75 columns.

No, <= 67 chars, not 75 chars.

This is especially important for resizing of windows or frames to fit their
widest line.


From (elisp) Documentation Tips:

  Format the documentation string so that it fits in an Emacs window
  on an 80-column screen.  It is a good idea for most lines to be no
  wider than 60 characters.  The first line should not be wider than
  67 characters or it will look bad in the output of `apropos'.

See also bugs #4162 and #3227.

Re: using libmagic in Emacs?

[Stefan Monnier]

> If we go this route, we should not load gnus/mailcap.el.

Nobody suggested otherwise until now (actually noone mentioned anything
close to mailcap in this thread, AFAICT).  Could you expand on what use
you were thinking of making of mailcap in this context?


        Stefan

Re: using libmagic in Emacs?

[Stefan Monnier]

>> +  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
>> +  rvs=magic_file (cookie, f);
>> +  if (rvs == NULL) goto libmagic_error;
>> +  Lisp_Object file_encoding = intern(rvs);  

> Is file_encoding supposed to be a valid encoding, one of those for
> which Emacs has a coding-system?  If so, perhaps you should make sure
> you indeed return a valid coding-system or its alias, or otherwise
> tell in the doc string that it's not guaranteed to be valid (so that
> the caller should validate it before using).

The simplest route is to return a string rather than a symbol.
That should clearly convey the idea that this may or may not be a valid
coding-system.


        Stefan

Re: Bidi support

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: cyd@stupidchicken.com,  emacs-devel@gnu.org
> Date: Fri, 21 Aug 2009 14:59:24 -0400
> 
> Has this branch been kept up-to-date w.r.t the trunk?

No.

> I'd guess not.  In that case, someone should do it.

I already did.  I have a source tree where the bidi code is merged
with the current trunk, and I merge them as needed all the time.
That's where I do all the development beyond what's on the bidi branch
(which is dead, as far as I'm concerned).  I can keep it that way
forever, but I'd prefer to have it in the repository soon, because
others might wish to work on it.

> Agreed.  The more I think about it, the more I think we need to open
> a new branch for "what will become emacs-24".  Kind of like what we did
> with the emacs-unicode branch.  I think bidi should be one of the first
> features to install on that branch.

Why not the other way around: make a branch for Emacs 23.x, and leave
Emacs 24 on the trunk?  I think Yidong suggested that, and I think
it's a better idea.  We never left the mainline of our development on
a branch before.

> I think it will stay unstable for too long, so it's not good enough for
> the current trunk (which I'd like to keep for shorter-term changes).

I guess that's a NO, but please note that this code, however unstable,
is never executed unless the user flips a variable.  So I don't see
how it can destabilize the default configuration by being dead
ballast.

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 892 bytes --]

> I suggest the following variation of it:
>
> 	 doc: /* Return a list describing the argument FILE-OR-BUFFER.
>
>   If FILE-OR-BUFFER is a file name, return information about that file.
...
>   given depends on your version of that database.  Often the MIME type is
>   less exact than the description.  */)

I used this description.

> Two more comments:
>
>  . I am not sure you need to push the file-or-buffer dichotomy to the
>    C level.  It is easy enough to do that in Lisp, or even in the
>    application, for that matter.  Why complicate a primitive to do
>    such a simple job?

Ok, removed it.

>  . You didn't say in the doc string whether MIME-ENCODING is
>    guaranteed to be a valid Emacs coding-system.  I think a user will
>    be desperate to know that.

Did like Stefan sugested, return a string.

Also improved GCPRO stuff, like Andreas suggested.

-- 
Joakim Verona

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic4.patch --]
[-- Type: text/x-patch, Size: 5853 bytes --]

diff --git a/configure.in b/configure.in
index f4096db..49a3f15 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([libmagic],[don't compile with libmagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_libmagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 425cf98..33d1a14 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -878,7 +879,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/fileio.c b/src/fileio.c
index 3702d4c..48a1ccd 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
 int write_region_inhibit_fsync;
 #endif
 
+#ifdef HAVE_LIBMAGIC
+#include <magic.h>
+#endif
+
 /* Non-zero means call move-file-to-trash in Fdelete_file or
    Fdelete_directory.  */
 int delete_by_moving_to_trash;
@@ -2997,6 +3001,78 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
 
 #endif /* HAVE_SYNC */
 
+#ifdef HAVE_LIBMAGIC
+DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
+	 doc: /* Return a list describing the argument FILENAME.
+
+
+  The return value is a list of the form 
+
+       (MIME-TYPE MIME-ENCODING DESCRIPTION)
+
+  MIME-TYPE and MIME-ENCODING are the MIME type and encoding suitable
+  for the file's contents, as determined by libmagic.
+  DESCRIPTION is the human readable descripton of the file type offered by
+  libmagic.
+
+  The function throws a file-error if libmagic cannot determine one of
+  the elements of the above list.
+
+  The default libmagic database is used, and the quality of information
+  given depends on your version of that database.  Often the MIME type is
+  less exact than the description.  */)
+  (filename)
+     Lisp_Object filename;
+{
+  CHECK_STRING (filename);
+  magic_t cookie=NULL;
+  char* f = NULL;
+  const char* rvs;
+  Lisp_Object file_description;
+  Lisp_Object file_mime;
+  Lisp_Object file_encoding;  
+  Lisp_Object rv;
+
+  Lisp_Object absname, encoded_absname;
+  struct gcpro gcpro1, gcpro2, gcpro3, gcpro4, gcpro5, gcpro6;
+
+  GCPRO6 (file_description, file_mime, file_encoding, rv, absname, encoded_absname);
+
+  absname = Fexpand_file_name (filename, current_buffer->directory);
+  f = SDATA(ENCODE_FILE (absname));
+
+  cookie = magic_open (MAGIC_ERROR);
+  if (cookie == NULL) goto libmagic_error;  
+  magic_load (cookie, NULL); /* load default database */
+
+  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
+  rvs = magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  file_mime = intern (rvs);
+
+  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  file_encoding = build_string(rvs);  
+
+  magic_setflags (cookie, MAGIC_NONE | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+
+  file_description = build_string (rvs);
+  rv = Fcons (file_mime, Fcons (file_encoding, Fcons (file_description, Qnil)));
+  
+  magic_close (cookie);
+  UNGCPRO;
+  return rv;
+ libmagic_error:
+  report_file_error("Libmagic error",Qnil);
+  if (cookie != NULL) magic_close (cookie);  
+  UNGCPRO;
+  return Qnil;
+}
+#endif
+
 DEFUN ("file-newer-than-file-p", Ffile_newer_than_file_p, Sfile_newer_than_file_p, 2, 2, 0,
        doc: /* Return t if file FILE1 is newer than file FILE2.
 If FILE1 does not exist, the answer is nil;
@@ -5781,6 +5857,9 @@ When non-nil, the function `move-file-to-trash' will be used by
 #ifdef HAVE_SYNC
   defsubr (&Sunix_sync);
 #endif
+#ifdef HAVE_LIBMAGIC
+    defsubr (&Slibmagic_file_internal);
+#endif
 }
 
 /* arch-tag: 64ba3fd7-f844-4fb2-ba4b-427eb928786c

Re: using libmagic in Emacs?

[Andreas Schwab]

joakim@verona.se writes:

> +  GCPRO6 (file_description, file_mime, file_encoding, rv, absname, encoded_absname);

That's too much.  You only need to protect variables used around calls
that can GC.  Arguments to lisp functions are implicitly protected.  For
example, there are no function calls during the lifetime of absname.
And encoded_absname is completely unused.

> + libmagic_error:
> +  report_file_error("Libmagic error",Qnil);
> +  if (cookie != NULL) magic_close (cookie);  

report_file_error throws, so you leak a resource.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Bidi support

[Stefan Monnier]

> I already did.  I have a source tree where the bidi code is merged
> with the current trunk, and I merge them as needed all the time.

Good, thank you.

>> Agreed.  The more I think about it, the more I think we need to open
>> a new branch for "what will become emacs-24".  Kind of like what we did
>> with the emacs-unicode branch.  I think bidi should be one of the first
>> features to install on that branch.

> Why not the other way around: make a branch for Emacs 23.x, and leave
> Emacs 24 on the trunk?  I think Yidong suggested that, and I think
> it's a better idea.

Sure.  I tend to forget about CVS's idea that one of the branches is
deemed special.  So yes, "open a new branch for emacw-24" here would
mean "create a new CVS branch for Emacs-23.2 and use the trunk for
Emacs-24".
[ I'm eagerly waiting to switch over to a system where
  branches are easier to use. ]

> We never left the mainline of our development on a branch before.

Actually we did for emacs-unicode ;-)
Not that it matters, tho.

>> I think it will stay unstable for too long, so it's not good enough for
>> the current trunk (which I'd like to keep for shorter-term changes).

> I guess that's a NO, but please note that this code, however unstable,
> is never executed unless the user flips a variable.  So I don't see
> how it can destabilize the default configuration by being
> dead ballast.

I know, but somehow having such experimental code there makes me uneasy.


        Stefan

Re: using libmagic in Emacs?

[Stephen J. Turnbull]

Stefan Monnier writes:

 > We need two functions:
 > - one implemented in C which provides the info from libmagic, no more no less.

+1

 > So yes, the second one can be called `file-mime-type', but the first
 > would better be called `file-magic' or somesuch.

Eli doesn't like that, and he's convinced me.  `file-type-by-magic'
or some such, I think.  Even if the reader hasn't had the benefit of a
classical education, they will have some idea of what's going on.

Bidi support

[Stephen J. Turnbull]

Stefan Monnier writes:

 > Agreed.  The more I think about it, the more I think we need to open
 > a new branch for "what will become emacs-24".

That's what I thought, too, about XEmacs 21.5.  I was wrong.  We ended
up having to uproot the trunk and move it to a branch, and graft the
21.5 branch back as the trunk.  Long-term development belongs either
on the trunk, or in feature branches.  Not on a long-term development
branch which collects several features.

Once you move to bzr, this will become less costly, but remember that
in bzr (like CVS, but not so disastrously as CVS) some branches are
more equal than others in the way they are presented to the user.
It's not like git where you just do

git branch emacs-23 master
git branch -f master emacs-24
git branch -D emacs-24            # optional

and everything's alright.

 > I think it will stay unstable for too long, so it's not good enough for
 > the current trunk (which I'd like to keep for shorter-term changes).

I know how you feel, but doing things this way is either going to be a
lot of work (synching "short-term changes" from the trunk to the
long-term branch -- in my experience, people work on features like
unicode and bidi in spurts, and they're pervasive changes so conflicts
are frequent if you come back every month or so), or discourage work
on the long-term branch (conflict resolution is enthusiasm-draining).

It also fails to encourage work on the instabilities by third parties.

I may be all wet; ask Ken'ichi and Miles how they feel about the long
stalls on the unicode and lexbind branches.  And maybe bzr will be
flexible enough to handle it, but you won't know that until Christmas,
I would guess.  I'm still finding new things I dislike about Mercurial
20 months after our conversion....

Re: Bidi support

[Eli Zaretskii]

> From: "Stephen J. Turnbull" <stephen@xemacs.org>
> Cc: Eli Zaretskii <eliz@gnu.org>,
>     cyd@stupidchicken.com,
>     emacs-devel@gnu.org
> Date: Sat, 22 Aug 2009 14:39:59 +0900
> 
> I know how you feel, but doing things this way is either going to be a
> lot of work (synching "short-term changes" from the trunk to the
> long-term branch -- in my experience, people work on features like
> unicode and bidi in spurts, and they're pervasive changes so conflicts
> are frequent if you come back every month or so), or discourage work
> on the long-term branch (conflict resolution is enthusiasm-draining).

I merge once a week, for this very reason.  So far, no conflicts,
since the changes are limited to the display engine, where no active
development happened for quite some time.

Also, all the changes for now have the form

  if (!bidi)
    {
      old code
    }
  else
    {
      new code
    }

and changes only happen in the `else' branch.  This decreases the
probability of conflicts even more (and also avoids destabilizing the
stable code of yore).

Once the infrastructure part is over, and people start changing Lisp
packages, then yes, I guess the probability of conflict will soar.

And as I wrote, I also think the trunk should be Emacs 24, while 23.x
should be on a branch.

Re: Bidi support

[Jason Rumney]

Eli Zaretskii wrote:
> Why not the other way around: make a branch for Emacs 23.x, and leave
> Emacs 24 on the trunk?  I think Yidong suggested that, and I think
> it's a better idea.  We never left the mainline of our development on
> a branch before.
>   

We did for both unicode, and for multi-tty. Once the code was usable on 
GNU/Linux and at least compilable and didn't break on all other 
platforms (which involved removing Carbon support, because noone wanted 
to work on it), it was merged back to the trunk.

We should probably aim to keep the branch period short, but it would be 
useful to check what you have now into a new branch so others can try it 
before it goes on the trunk.

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 835 bytes --]

Andreas Schwab <schwab@linux-m68k.org> writes:

> joakim@verona.se writes:
>
>> +  GCPRO6 (file_description, file_mime, file_encoding, rv, absname, encoded_absname);
>
> That's too much.  You only need to protect variables used around calls
> that can GC.  Arguments to lisp functions are implicitly protected.  For
> example, there are no function calls during the lifetime of absname.
> And encoded_absname is completely unused.

It seems to me I only need to protect f, which I would do by GCPRO:ing
absname. Since this is aparently wrong, I will leave it like it is,
since it doesnt hurt to GCPRO too much. (?)

>> + libmagic_error:
>> +  report_file_error("Libmagic error",Qnil);
>> +  if (cookie != NULL) magic_close (cookie);  
>
> report_file_error throws, so you leak a resource.

Fixed I think.

> Andreas.
-- 
Joakim Verona

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic5.patch --]
[-- Type: text/x-patch, Size: 5853 bytes --]

diff --git a/configure.in b/configure.in
index f4096db..49a3f15 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([libmagic],[don't compile with libmagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_libmagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 425cf98..33d1a14 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -878,7 +879,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/fileio.c b/src/fileio.c
index 3702d4c..48a1ccd 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
 int write_region_inhibit_fsync;
 #endif
 
+#ifdef HAVE_LIBMAGIC
+#include <magic.h>
+#endif
+
 /* Non-zero means call move-file-to-trash in Fdelete_file or
    Fdelete_directory.  */
 int delete_by_moving_to_trash;
@@ -2997,6 +3001,78 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
 
 #endif /* HAVE_SYNC */
 
+#ifdef HAVE_LIBMAGIC
+DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
+	 doc: /* Return a list describing the argument FILENAME.
+
+
+  The return value is a list of the form 
+
+       (MIME-TYPE MIME-ENCODING DESCRIPTION)
+
+  MIME-TYPE and MIME-ENCODING are the MIME type and encoding suitable
+  for the file's contents, as determined by libmagic.
+  DESCRIPTION is the human readable descripton of the file type offered by
+  libmagic.
+
+  The function throws a file-error if libmagic cannot determine one of
+  the elements of the above list.
+
+  The default libmagic database is used, and the quality of information
+  given depends on your version of that database.  Often the MIME type is
+  less exact than the description.  */)
+  (filename)
+     Lisp_Object filename;
+{
+  CHECK_STRING (filename);
+  magic_t cookie=NULL;
+  char* f = NULL;
+  const char* rvs;
+  Lisp_Object file_description;
+  Lisp_Object file_mime;
+  Lisp_Object file_encoding;  
+  Lisp_Object rv;
+
+  Lisp_Object absname, encoded_absname;
+  struct gcpro gcpro1, gcpro2, gcpro3, gcpro4, gcpro5, gcpro6;
+
+  GCPRO6 (file_description, file_mime, file_encoding, rv, absname, encoded_absname);
+
+  absname = Fexpand_file_name (filename, current_buffer->directory);
+  f = SDATA(ENCODE_FILE (absname));
+
+  cookie = magic_open (MAGIC_ERROR);
+  if (cookie == NULL) goto libmagic_error;  
+  magic_load (cookie, NULL); /* load default database */
+
+  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
+  rvs = magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  file_mime = intern (rvs);
+
+  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+  file_encoding = build_string(rvs);  
+
+  magic_setflags (cookie, MAGIC_NONE | MAGIC_ERROR);
+  rvs=magic_file (cookie, f);
+  if (rvs == NULL) goto libmagic_error;
+
+  file_description = build_string (rvs);
+  rv = Fcons (file_mime, Fcons (file_encoding, Fcons (file_description, Qnil)));
+  
+  magic_close (cookie);
+  UNGCPRO;
+  return rv;
+ libmagic_error:
+  report_file_error("Libmagic error",Qnil);
+  if (cookie != NULL) magic_close (cookie);  
+  UNGCPRO;
+  return Qnil;
+}
+#endif
+
 DEFUN ("file-newer-than-file-p", Ffile_newer_than_file_p, Sfile_newer_than_file_p, 2, 2, 0,
        doc: /* Return t if file FILE1 is newer than file FILE2.
 If FILE1 does not exist, the answer is nil;
@@ -5781,6 +5857,9 @@ When non-nil, the function `move-file-to-trash' will be used by
 #ifdef HAVE_SYNC
   defsubr (&Sunix_sync);
 #endif
+#ifdef HAVE_LIBMAGIC
+    defsubr (&Slibmagic_file_internal);
+#endif
 }
 
 /* arch-tag: 64ba3fd7-f844-4fb2-ba4b-427eb928786c

Re: using libmagic in Emacs?

[Ken Raeburn]

On Aug 22, 2009, at 16:18, joakim@verona.se wrote:
> Andreas Schwab <schwab@linux-m68k.org> writes:
> joakim@verona.se writes:
>>
>>> +  GCPRO6 (file_description, file_mime, file_encoding, rv,  
>>> absname, encoded_absname);
>>
>> That's too much.  You only need to protect variables used around  
>> calls
>> that can GC.  Arguments to lisp functions are implicitly  
>> protected.  For
>> example, there are no function calls during the lifetime of absname.
>> And encoded_absname is completely unused.
>
> It seems to me I only need to protect f, which I would do by GCPRO:ing
> absname. Since this is aparently wrong, I will leave it like it is,
> since it doesnt hurt to GCPRO too much. (?)

If ENCODE_FILE returns a new lisp string object, you need to GCPRO  
that object, not absname.  After the call to ENCODE_FILE, absname is  
unused, so it won't need protection.  In fact, it looks to me like  
after that point, GC isn't possible, so I'm not sure anything needs  
GCPRO'tection here.

>
>>> + libmagic_error:
>>> +  report_file_error("Libmagic error",Qnil);
>>> +  if (cookie != NULL) magic_close (cookie);
>>
>> report_file_error throws, so you leak a resource.
>
> Fixed I think.

No, you're still trying to call magic_close after report_file_error  
returns, which it won't.

> +{
> +  CHECK_STRING (filename);
> +  magic_t cookie=NULL;
> +  char* f = NULL;

CHECK_STRING is executable code, and should be moved down after the  
variable declarations.

> +  const char* rvs;
> +  Lisp_Object file_description;
> +  Lisp_Object file_mime;
> +  Lisp_Object file_encoding;
> +  Lisp_Object rv;
> +
> +  Lisp_Object absname, encoded_absname;
> +  struct gcpro gcpro1, gcpro2, gcpro3, gcpro4, gcpro5, gcpro6;
> +
> +  GCPRO6 (file_description, file_mime, file_encoding, rv, absname,  
> encoded_absname);

It seems to be common -- I'm not sure if it's required, but I would  
conservatively assume so -- for any local variable GCPRO'd to get  
initialized before any possible call to garbage collection, so the  
precise(?) garbage collector won't be scanning random stack values and  
thinking they're lisp objects; if the initialization is unclear, often  
that means simply assigning Qnil just before or after the GCPRO call.

Different GC marking strategies are used on different platforms, so  
the lack of an obvious problem on one platform doesn't mean the code  
will work okay on another.

Ken

Re: using libmagic in Emacs?

[Juri Linkov]

>     >> For instance, in "image.el" there is functionality to look at
>     >> magic numbers in image files.
>
>     image.el doesn't recognize some rare JPEG formats, so libmagic
>     will be useful here.
>
> Extending image.el mightbe a lot easier than other solutions.

The problem is that `image-jpeg-p' in image.el refuses to accept
non-JFIF JPEG image files whereas Emacs can correctly display them
when tests in `image-jpeg-p' are ignored.

Using libmagic means looking only for 2 bytes 0xffd8 (a magic number
of JPEG files) as described by the magic number file:

  0	beshort		0xffd8		JPEG image data

It seems this is enough to determine JPEG files.  But I'm not confident
about removing additional tests from `image-jpeg-p'.  We could keep the
current rules in image.el as a fall-back when libmagic is not available.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Stefan Monnier]

>> So yes, the second one can be called `file-mime-type', but the first
>> would better be called `file-magic' or somesuch.

> Eli doesn't like that, and he's convinced me.  `file-type-by-magic'
> or some such, I think.  Even if the reader hasn't had the benefit of a
> classical education, they will have some idea of what's going on.

As long as `magic' is in the name, that's OK.


        Stefan

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: joakim@verona.se
> Cc: Eli Zaretskii <eliz@gnu.org>, monnier@iro.umontreal.ca,
>         emacs-devel@gnu.org
> Date: Sat, 22 Aug 2009 22:18:26 +0200
> 
> +  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
> +  rvs = magic_file (cookie, f);
> +  if (rvs == NULL) goto libmagic_error;
> +  file_mime = intern (rvs);
> +
> +  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
> +  rvs=magic_file (cookie, f);
> +  if (rvs == NULL) goto libmagic_error;
> +  file_encoding = build_string(rvs);  

Since you are returning strings for MIME type and MIME encoding, not
symbols, I suggest to state that in the doc string.  Normally, when we
say "SOMETHING is an encoding", we mean it's a symbol.

Alternatively, use MIME-ENCODING-NAME etc., to indicate that it's just
a name of the thing, not the thing itself.

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 2131 bytes --]

Ken Raeburn <raeburn@raeburn.org> writes:

> On Aug 22, 2009, at 16:18, joakim@verona.se wrote:
>> Andreas Schwab <schwab@linux-m68k.org> writes:
>> joakim@verona.se writes:
>>>
>>>> +  GCPRO6 (file_description, file_mime, file_encoding, rv,
>>>> absname, encoded_absname);
>>>
>>> That's too much.  You only need to protect variables used around
>>> calls
>>> that can GC.  Arguments to lisp functions are implicitly protected.
>>> For
>>> example, there are no function calls during the lifetime of absname.
>>> And encoded_absname is completely unused.
>>
>> It seems to me I only need to protect f, which I would do by GCPRO:ing
>> absname. Since this is aparently wrong, I will leave it like it is,
>> since it doesnt hurt to GCPRO too much. (?)
>
> If ENCODE_FILE returns a new lisp string object, you need to GCPRO
> that object, not absname.  After the call to ENCODE_FILE, absname is
> unused, so it won't need protection.  In fact, it looks to me like
> after that point, GC isn't possible, so I'm not sure anything needs
> GCPRO'tection here.
>

I seem to be having trouble with GCPRO. Now I've marked the places I
believe might gc in the code.

>>> report_file_error throws, so you leak a resource.
>>
>> Fixed I think.
>
> No, you're still trying to call magic_close after report_file_error
> returns, which it won't.

Maybe I sent the wrong patch revision last time, better now then?

> CHECK_STRING is executable code, and should be moved down after the
> variable declarations.

same here.


> It seems to be common -- I'm not sure if it's required, but I would
> conservatively assume so -- for any local variable GCPRO'd to get
> initialized before any possible call to garbage collection, so the
> precise(?) garbage collector won't be scanning random stack values and
> thinking they're lisp objects; if the initialization is unclear, often
> that means simply assigning Qnil just before or after the GCPRO call.
>
> Different GC marking strategies are used on different platforms, so
> the lack of an obvious problem on one platform doesn't mean the code
> will work okay on another.
>
> Ken
-- 
Joakim Verona

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic6.patch --]
[-- Type: text/x-patch, Size: 5988 bytes --]

diff --git a/configure.in b/configure.in
index f4096db..49a3f15 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([libmagic],[don't compile with libmagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2223,6 +2225,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_libmagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2954,6 +2969,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 425cf98..33d1a14 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -420,6 +420,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -878,7 +879,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/fileio.c b/src/fileio.c
index 3702d4c..0061981 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
 int write_region_inhibit_fsync;
 #endif
 
+#ifdef HAVE_LIBMAGIC
+#include <magic.h>
+#endif
+
 /* Non-zero means call move-file-to-trash in Fdelete_file or
    Fdelete_directory.  */
 int delete_by_moving_to_trash;
@@ -2997,6 +3001,81 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
 
 #endif /* HAVE_SYNC */
 
+#ifdef HAVE_LIBMAGIC
+DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
+	 doc: /* Return a list describing the argument FILENAME.
+
+
+  The return value is a list of the form 
+
+       (MIME-TYPE MIME-ENCODING-NAME DESCRIPTION)
+
+       MIME-TYPE and MIME-ENCODING-NAME are the MIME type and encoding
+  suitable for the file's contents, as determined by libmagic.
+  DESCRIPTION is the human readable descripton of the file type
+  offered by libmagic.
+
+  The function throws a file-error if libmagic cannot determine one of
+  the elements of the above list.
+
+  The default libmagic database is used, and the quality of
+  information given depends on your version of that database.  Often
+  the MIME type is less exact than the description.  */)
+  (filename)
+     Lisp_Object filename;
+{
+  magic_t cookie=NULL;
+  char* f = NULL;
+  const char* returnvaluestr;
+  Lisp_Object file_description;
+  Lisp_Object file_mime;
+  Lisp_Object file_encoding;  
+  Lisp_Object returnvalue;
+  Lisp_Object absname;
+  int errsave;
+  struct gcpro gcpro1, gcpro2;
+  
+  CHECK_STRING (filename);
+
+  GCPRO2 (filename, absname);
+  absname = Fexpand_file_name (filename, current_buffer->directory); //might gc
+  f = SDATA(ENCODE_FILE (absname));//might gc
+  UNGCPRO;
+  
+  cookie = magic_open (MAGIC_ERROR);
+  if (cookie == NULL) goto libmagic_error;  
+  magic_load (cookie, NULL); /* load default database */
+
+  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
+  returnvaluestr = magic_file (cookie, f);
+  if (returnvaluestr == NULL) goto libmagic_error;
+  file_mime = intern (returnvaluestr);
+
+  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
+  returnvaluestr=magic_file (cookie, f);
+  if (returnvaluestr == NULL) goto libmagic_error;
+  file_encoding = build_string(returnvaluestr);  
+
+  magic_setflags (cookie, MAGIC_NONE | MAGIC_ERROR);
+  returnvaluestr=magic_file (cookie, f);
+  if (returnvaluestr == NULL) goto libmagic_error;
+
+  file_description = build_string (returnvaluestr); 
+  returnvalue = Fcons (file_mime, Fcons (file_encoding, Fcons (file_description, Qnil))); //might gc
+  
+  magic_close (cookie);
+
+  return returnvalue;
+ libmagic_error:
+  UNGCPRO;
+  errsave=errno;
+  if (cookie != NULL) magic_close (cookie);
+  errno=errsave;
+  report_file_error("Libmagic error",Qnil);
+  return Qnil;
+}
+#endif
+
 DEFUN ("file-newer-than-file-p", Ffile_newer_than_file_p, Sfile_newer_than_file_p, 2, 2, 0,
        doc: /* Return t if file FILE1 is newer than file FILE2.
 If FILE1 does not exist, the answer is nil;
@@ -5781,6 +5860,9 @@ When non-nil, the function `move-file-to-trash' will be used by
 #ifdef HAVE_SYNC
   defsubr (&Sunix_sync);
 #endif
+#ifdef HAVE_LIBMAGIC
+    defsubr (&Slibmagic_file_internal);
+#endif
 }
 
 /* arch-tag: 64ba3fd7-f844-4fb2-ba4b-427eb928786c

Re: using libmagic in Emacs?

[Richard Stallman]

    The problem is that `image-jpeg-p' in image.el refuses to accept
    non-JFIF JPEG image files whereas Emacs can correctly display them
    when tests in `image-jpeg-p' are ignored.

    Using libmagic means looking only for 2 bytes 0xffd8 (a magic number
    of JPEG files) as described by the magic number file:

      0	beshort		0xffd8		JPEG image data

    It seems this is enough to determine JPEG files.  But I'm not confident
    about removing additional tests from `image-jpeg-p'.  We could keep the
    current rules in image.el as a fall-back when libmagic is not available.

Whatever we do with the function `image-jpeg-p', we could easily make
Emacs test these two bytes.  It makes no sense to install code to link
with libmagic just to handle that and a few other similar things.

Meanwhile, for operations less common and important than visiting a file,
running `file' is easy to do.

Combining those two approaches seems much better than adding code to
link with libmagic.

Re: using libmagic in Emacs?

[Juri Linkov]

> Whatever we do with the function `image-jpeg-p', we could easily make
> Emacs test these two bytes.  It makes no sense to install code to link
> with libmagic just to handle that and a few other similar things.
>
> Meanwhile, for operations less common and important than visiting a file,
> running `file' is easy to do.
>
> Combining those two approaches seems much better than adding code to
> link with libmagic.

Of course, before adding code to link with libmagic we should analyze
how useful it would be.  I see its usefulness at least in the following
areas:

1. Archive file types

A popular way to create new archive file types nowadays is to register
a new file extension with the old data compression and archive format.

For instance, Java archive files have the .jar extension but build on
the ZIP file format, so they can be visited in Emacs with the help of
`archive-mode'.  Enterprise Java archives with the .ear extension
and Web application Java archives with the .war extension all are
based on the ZIP file format as well as OpenDocument files with
extensions .odt .ods .odb .odp .odg .odf, Firefox add-ons (.xpi),
Keyhole Markup (.kmz), and many other file types that can be potentially
opened in Emacs if were identified as archive files by libmagic.

We can't track and add all new formats.  This is the main task of libmagic.

2. Image file types

Using ImageMagick in Emacs can support over 100 image file formats.
It won't possible to recognize all them without libmagic.

3. MIME-types handling

Emacs can process different MIME-type detected by libmagic.
Even when Emacs has no special handling for a file type, it is
still useful to let Emacs run an external program associated
with its MIME-type for users who prefer running programs
(including GUI programs) from Emacs instead of using a window
manager's application menu.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: Bidi support

[Kenichi Handa]

In article <87bpm84dao.fsf@uwakimon.sk.tsukuba.ac.jp>, "Stephen J. Turnbull" <stephen@xemacs.org> writes:

> Stefan Monnier writes:
> Agreed.  The more I think about it, the more I think we need to open
> a new branch for "what will become emacs-24".

> That's what I thought, too, about XEmacs 21.5.  I was wrong.  We ended
> up having to uproot the trunk and move it to a branch, and graft the
> 21.5 branch back as the trunk.  Long-term development belongs either
> on the trunk, or in feature branches.  Not on a long-term development
> branch which collects several features.

Having an separate branch has at least one merit.  As far as
it is branched from a fairly stable version, a person
working on the branch can be sure that any problem in that
branch is caused by his change.

For the case of bidi, if there's a plan of another big
change in the display engine, the above merit is big.  With
a separate branch, people working on bidi code don't have to
be annoyed by bugs of that another change.  Otherwise, I
think having bidi code in the trunk is better.

By the way, the case of emacs-unicode is very special.  It
simply can't be in the trunk while developing because the
new unicode feature can't be toggled.

---
Kenichi Handa
handa@m17n.org

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: joakim@verona.se
> Date: Mon, 24 Aug 2009 01:38:26 +0200
> Cc: emacs-devel emacs-devel <emacs-devel@gnu.org>
> 
> +  f = SDATA(ENCODE_FILE (absname));//might gc

No C99 comments, please.

Re: Bidi support

[Eli Zaretskii]

> From: Kenichi Handa <handa@m17n.org>
> CC: monnier@iro.umontreal.ca, eliz@gnu.org, cyd@stupidchicken.com,
>         emacs-devel@gnu.org
> Date: Mon, 24 Aug 2009 10:45:05 +0900
> 
> By the way, the case of emacs-unicode is very special.  It
> simply can't be in the trunk while developing because the
> new unicode feature can't be toggled.

Exactly, and that's precisely why the bidi development _can_ be done
on the trunk without the burden of distinguishing its bugs from the
others: toggle the feature off, and if the bug persists, it's not from
bidi.

OTOH, the HUGE advantage of working on the trunk is that you don't
need to merge all the time, or risk falling out of sync.  You also
don't inherit random bugs that existed at the time of the branch
creation.

Re: Bidi support

[Stephen J. Turnbull]

Kenichi Handa writes:
 > In article <87bpm84dao.fsf@uwakimon.sk.tsukuba.ac.jp>, "Stephen J. Turnbull" <stephen@xemacs.org> writes:
 > 
 > > Stefan Monnier writes:
 > > Agreed.  The more I think about it, the more I think we need to open
 > > a new branch for "what will become emacs-24".
 > 
 > > That's what I thought, too, about XEmacs 21.5.  I was wrong.  We ended
 > > up having to uproot the trunk and move it to a branch, and graft the
 > > 21.5 branch back as the trunk.  Long-term development belongs either
 > > on the trunk, or in feature branches.  Not on a long-term development
 > > branch which collects several features.

 > Having an separate branch has at least one merit.  As far as
 > it is branched from a fairly stable version,

What you describe is what I mean by "feature branch".  Features
branches are a tried and true way to work; I do not mean to say "don't
use feature branches".

 > For the case of bidi, if there's a plan of another big
 > change in the display engine, the above merit is big.

bidi already has a branch or a repository or something.  It only needs
to be canonized as "accepted in principle" for v24, and given an
official URL.  My understanding of what Stefan proposed is something
different: that as the maintainers decide that some features are
important to add, they be merged to the "for v24" branch: bidi with
lexbind with ....

 > By the way, the case of emacs-unicode is very special.  It
 > simply can't be in the trunk while developing because the
 > new unicode feature can't be toggled.

By "can't", I guess you mean you didn't design it to be toggled?  Ben
Wing worked out how to have toggle-able buffer formats in 2002 (then
disappeared from XEmacs, unfortunately, but the infrastructure is
present).  I'm not saying it's a good idea, but it's possible.

Re: Bidi support

[Kenichi Handa]

In article <83y6p9ewgj.fsf@gnu.org>, Eli Zaretskii <eliz@gnu.org> writes:

> > By the way, the case of emacs-unicode is very special.  It
> > simply can't be in the trunk while developing because the
> > new unicode feature can't be toggled.

> Exactly, and that's precisely why the bidi development _can_ be done
> on the trunk without the burden of distinguishing its bugs from the
> others: toggle the feature off, and if the bug persists, it's not from
> bidi.

Even if that bug is not from bidi, as far as bidi support
suffers from it, the work for bidi support must be suspended
until that bug is fixed.  For instance, please consider the
situation that face-handling code gets unstable at some
point.  If we are working on a bug that bidi-text can't be
displayed by a correct face (just a hypothetical bug), that
work must be suspended.

> OTOH, the HUGE advantage of working on the trunk is that you don't
> need to merge all the time, or risk falling out of sync.  You also
> don't inherit random bugs that existed at the time of the branch
> creation.

I understand that merit too.  I even tend to agree on having
the bidi code in the trunk.  I just wanted to point out the
possibility of the above demerit.

---
Kenichi Handa
handa@m17n.org

Re: using libmagic in Emacs?

[joakim]

Juri Linkov <juri@jurta.org> writes:
>
> Of course, before adding code to link with libmagic we should analyze
> how useful it would be.  I see its usefulness at least in the following
> areas:
>
> 1. Archive file types
...
>
> We can't track and add all new formats.  This is the main task of libmagic.
>
> 2. Image file types
>
> Using ImageMagick in Emacs can support over 100 image file formats.
> It won't possible to recognize all them without libmagic.
>
> 3. MIME-types handling
>
> Emacs can process different MIME-type detected by libmagic.
> Even when Emacs has no special handling for a file type, it is
> still useful to let Emacs run an external program associated
> with its MIME-type for users who prefer running programs
> (including GUI programs) from Emacs instead of using a window
> manager's application menu.

I agree completely with Juri, it is these two cases that motivates me to
work on the libmagic support.

There are a great deal of formats Emacs is able to open, but not to
recognize, such as all the many different Java archive formats Juri
mentions. There are compressed image formats like SVG. 

Also, if we decide to merge the imagemagick patch, hundreds of new
image file formats will be supported, that libmagic will help identify.

Notice that I do not propose to replace Emacs current file recognition,
only to expand it when libmagic is available. We can also expand a bit
of the current handling to take care of a few well known cases, such as
the jpeg one. If no libmagic, then Emacs will behave as today, or
slightly better. If libmagic, many new file formats will open
correctly.

I honestly cant see any drawbacks with this aproach, other than me
consuming some list resources while developing the patch. I hope to be
able to reciprocate with improved documentation for developing Emacs
primitives.

Lets also not forget the friendly competition from other free text
editors. Emacs IMHO does the right thing with files more often than
other editors, lets improve on this strength!


--
Joakim Verona

Re: using libmagic in Emacs?

[joakim]

[-- Attachment #1: Type: text/plain, Size: 279 bytes --]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: joakim@verona.se
>> Date: Mon, 24 Aug 2009 01:38:26 +0200
>> Cc: emacs-devel emacs-devel <emacs-devel@gnu.org>
>> 
>> +  f = SDATA(ENCODE_FILE (absname));//might gc
>
> No C99 comments, please.

This time I compiled with -std=c89.


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: filemagic7.patch --]
[-- Type: text/x-patch, Size: 6002 bytes --]

diff --git a/configure.in b/configure.in
index e578f76..90e67e7 100644
--- a/configure.in
+++ b/configure.in
@@ -137,6 +137,8 @@ OPTION_DEFAULT_ON([xft],[don't use XFT for anti aliased fonts])
 OPTION_DEFAULT_ON([libotf],[don't use libotf for OpenType font support])
 OPTION_DEFAULT_ON([m17n-flt],[don't use m17n-flt for text shaping])
 
+OPTION_DEFAULT_ON([libmagic],[don't compile with libmagic support])
+
 OPTION_DEFAULT_ON([toolkit-scroll-bars],[don't use Motif or Xaw3d scroll bars])
 OPTION_DEFAULT_ON([xaw3d],[don't use Xaw3d])
 OPTION_DEFAULT_ON([xim],[don't use X11 XIM])
@@ -2225,6 +2227,19 @@ if test x"$ac_cv_func_alloca_works" != xyes; then
    AC_MSG_ERROR( [a system implementation of alloca is required] )
 fi
 
+
+HAVE_LIBMAGIC=no
+if test "${with_libmagic}" != "no"; then
+  #libmagic support
+  AC_CHECK_HEADERS(magic.h, [  AC_CHECK_LIB(magic,magic_open,HAVE_LIBMAGIC=yes) ])
+fi
+
+if test "${HAVE_LIBMAGIC}" = "yes"; then
+  LIBMAGIC=-lmagic
+  AC_SUBST(LIBMAGIC)
+  AC_DEFINE(HAVE_LIBMAGIC, 1, [Define to 1 if using libmagic.])  
+fi
+
 # fmod, logb, and frexp are found in -lm on most systems.
 # On HPUX 9.01, -lm does not contain logb, so check for sqrt.
 AC_CHECK_LIB(m, sqrt)
@@ -2959,6 +2974,7 @@ echo "  Does Emacs use -lpng?                                   ${HAVE_PNG}"
 echo "  Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}"
 echo "  Does Emacs use -lgpm?                                   ${HAVE_GPM}"
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
+echo "  Does Emacs use -lmagic?                                 ${HAVE_LIBMAGIC}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"
diff --git a/src/Makefile.in b/src/Makefile.in
index 567bff9..ac30bc2 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -422,6 +422,7 @@ LIBX= $(LIBXMENU) LD_SWITCH_X_SITE
 #endif /* not HAVE_LIBRESOLV */
 
 LIBSOUND= @LIBSOUND@
+LIBMAGIC= @LIBMAGIC@
 CFLAGS_SOUND= @CFLAGS_SOUND@
 
 RSVG_LIBS= @RSVG_LIBS@
@@ -880,7 +881,7 @@ SOME_MACHINE_LISP = ../lisp/mouse.elc \
    duplicated symbols.  If the standard libraries were compiled
    with GCC, we might need gnulib again after them.  */
 
-LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(RSVG_LIBS) $(DBUS_LIBS) \
+LIBES = $(LOADLIBES) $(LIBS) $(LIBX) $(LIBSOUND) $(LIBMAGIC) $(RSVG_LIBS) $(DBUS_LIBS) \
    LIBGPM LIBRESOLV LIBS_SYSTEM LIBS_MACHINE LIBS_TERMCAP \
    LIBS_DEBUG $(GETLOADAVG_LIBS) \
    @FREETYPE_LIBS@ @FONTCONFIG_LIBS@ @LIBOTF_LIBS@ @M17N_FLT_LIBS@ \
diff --git a/src/fileio.c b/src/fileio.c
index 3702d4c..568728b 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -205,6 +205,10 @@ Lisp_Object Vdirectory_sep_char;
 int write_region_inhibit_fsync;
 #endif
 
+#ifdef HAVE_LIBMAGIC
+#include <magic.h>
+#endif
+
 /* Non-zero means call move-file-to-trash in Fdelete_file or
    Fdelete_directory.  */
 int delete_by_moving_to_trash;
@@ -2997,6 +3001,81 @@ DEFUN ("unix-sync", Funix_sync, Sunix_sync, 0, 0, "",
 
 #endif /* HAVE_SYNC */
 
+#ifdef HAVE_LIBMAGIC
+DEFUN ("libmagic-file-internal", Flibmagic_file_internal, Slibmagic_file_internal, 1,1,0,
+	 doc: /* Return a list describing the argument FILENAME.
+
+
+  The return value is a list of the form 
+
+       (MIME-TYPE MIME-ENCODING-NAME DESCRIPTION)
+
+       MIME-TYPE and MIME-ENCODING-NAME are the MIME type and encoding
+  suitable for the file's contents, as determined by libmagic.
+  DESCRIPTION is the human readable descripton of the file type
+  offered by libmagic.
+
+  The function throws a file-error if libmagic cannot determine one of
+  the elements of the above list.
+
+  The default libmagic database is used, and the quality of
+  information given depends on your version of that database.  Often
+  the MIME type is less exact than the description.  */)
+  (filename)
+     Lisp_Object filename;
+{
+  magic_t cookie=NULL;
+  char* f = NULL;
+  const char* returnvaluestr;
+  Lisp_Object file_description;
+  Lisp_Object file_mime;
+  Lisp_Object file_encoding;  
+  Lisp_Object returnvalue;
+  Lisp_Object absname;
+  int errsave;
+  struct gcpro gcpro1;
+  
+  CHECK_STRING (filename);
+
+  GCPRO1 (absname);
+  absname = Fexpand_file_name (filename, current_buffer->directory); /* might gc */
+  absname = ENCODE_FILE (absname);/* might gc */
+  f = SDATA(absname);
+  
+  cookie = magic_open (MAGIC_ERROR);
+  if (cookie == NULL) goto libmagic_error;  
+  magic_load (cookie, NULL); /* load default database */
+
+  magic_setflags (cookie, MAGIC_MIME_TYPE | MAGIC_ERROR);  
+  returnvaluestr = magic_file (cookie, f);
+  if (returnvaluestr == NULL) goto libmagic_error;
+  file_mime = intern (returnvaluestr);
+
+  magic_setflags (cookie, MAGIC_MIME_ENCODING | MAGIC_ERROR);
+  returnvaluestr=magic_file (cookie, f);
+  if (returnvaluestr == NULL) goto libmagic_error;
+  file_encoding = build_string(returnvaluestr);  
+
+  magic_setflags (cookie, MAGIC_NONE | MAGIC_ERROR);
+  returnvaluestr=magic_file (cookie, f);
+  if (returnvaluestr == NULL) goto libmagic_error;
+
+  file_description = build_string (returnvaluestr); 
+  returnvalue = Fcons (file_mime, Fcons (file_encoding, Fcons (file_description, Qnil))); /* might gc */
+  
+  magic_close (cookie);
+  UNGCPRO;
+  return returnvalue;
+ libmagic_error:
+  UNGCPRO;
+  errsave=errno;
+  if (cookie != NULL) magic_close (cookie);
+  errno=errsave;
+  report_file_error("Libmagic error",Qnil);
+  return Qnil;
+}
+#endif
+
 DEFUN ("file-newer-than-file-p", Ffile_newer_than_file_p, Sfile_newer_than_file_p, 2, 2, 0,
        doc: /* Return t if file FILE1 is newer than file FILE2.
 If FILE1 does not exist, the answer is nil;
@@ -5781,6 +5860,9 @@ When non-nil, the function `move-file-to-trash' will be used by
 #ifdef HAVE_SYNC
   defsubr (&Sunix_sync);
 #endif
+#ifdef HAVE_LIBMAGIC
+    defsubr (&Slibmagic_file_internal);
+#endif
 }
 
 /* arch-tag: 64ba3fd7-f844-4fb2-ba4b-427eb928786c

[-- Attachment #3: Type: text/plain, Size: 19 bytes --]


-- 
Joakim Verona

Re: using libmagic in Emacs?

[Richard Stallman]

    For instance, Java archive files have the .jar extension but build on
    the ZIP file format, so they can be visited in Emacs with the help of
    `archive-mode'.  Enterprise Java archives with the .ear extension
    and Web application Java archives with the .war extension all are
    based on the ZIP file format as well as OpenDocument files with
    extensions .odt .ods .odb .odp .odg .odf, Firefox add-ons (.xpi),
    Keyhole Markup (.kmz), and many other file types that can be potentially
    opened in Emacs if were identified as archive files by libmagic.

How hard would it be to change the code in Emacs to recognize these
using the existing mechanism?

    Using ImageMagick in Emacs can support over 100 image file formats.
    It won't possible to recognize all them without libmagic.

Maybe this is useful.  Is there an easy way to recognize files that
could be passed to ImageMagick?

    Emacs can process different MIME-type detected by libmagic.

That is not useful for visiting files in Emacs, since Emacs has no
special handling for many of these mime types.

If some other Lisp code is interested in the mime type of a file,
there is a much easier way to find it out: run `file'.
To complicate Emacs with another library just to make that operation
a little faster is a step in the wrong direction.

Re: using libmagic in Emacs?

[Miles Bader]

Richard Stallman <rms@gnu.org> writes:
> If some other Lisp code is interested in the mime type of a file,
> there is a much easier way to find it out: run `file'.

Well, not entirely trivial of course, since Emacs then needs to
interpret the results from the file command.

> To complicate Emacs with another library just to make that operation
> a little faster is a step in the wrong direction.

I wonder how hard it would be to have some elisp that understands the
"magic" rules that the file command uses... at first glance, they don't
seem particularly complex; e.g., this is the first entry from
"/usr/share/file/magic":

   0	lelong		0xc3cbc6c5	RISC OS Chunk data
   >12	string		OBJ_		\b, AOF object
   >12	string		LIB_		\b, ALF library

If there was such elisp code, Emacs could use any magic rules file on
the system, and in addition, could distribute it's own (perhaps smaller)
set.

-Miles

-- 
自らを空にして、心を開く時、道は開かれる

Re: using libmagic in Emacs?

[joakim]

Miles Bader <miles@gnu.org> writes:

> Richard Stallman <rms@gnu.org> writes:
>> If some other Lisp code is interested in the mime type of a file,
>> there is a much easier way to find it out: run `file'.
>
> Well, not entirely trivial of course, since Emacs then needs to
> interpret the results from the file command.
>
>> To complicate Emacs with another library just to make that operation
>> a little faster is a step in the wrong direction.
>
> I wonder how hard it would be to have some elisp that understands the
> "magic" rules that the file command uses... at first glance, they don't
> seem particularly complex; e.g., this is the first entry from
> "/usr/share/file/magic":
>
>    0	lelong		0xc3cbc6c5	RISC OS Chunk data
>    >12	string		OBJ_		\b, AOF object
>    >12	string		LIB_		\b, ALF library
>
> If there was such elisp code, Emacs could use any magic rules file on
> the system, and in addition, could distribute it's own (perhaps smaller)
> set.

I agree that the main benefit of using libmagic is getting access to the
libmagic database. 

> -Miles
-- 
Joakim Verona

Re: using libmagic in Emacs?

[James Cloos]

>>>>> "Miles" == Miles Bader <miles@gnu.org> writes:

Miles> I wonder how hard it would be to have some elisp that understands
Miles> the "magic" rules that the file command uses...

It shouldn't be too hard, but note that the current versions of file do
not install the text-format magic file, but rather a compiled .mgc file
instead.

The format of the text file is documented in the magic(4) man page.
(Which ought to be in section 5....)  I don't see any documentation
of the .mgc files, but there may be in the src.

-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6

Re: using libmagic in Emacs?

[Stefan Monnier]

> If some other Lisp code is interested in the mime type of a file,
> there is a much easier way to find it out: run `file'.

Actually, running `file' might be a useful fallback (especially if run
via process-file so it also works on remote files, contrary to
libmagic).

Also, looking at the way the magic database works, it seems that we
might want to run `file-type-by-magic' on a buffer's content as well.

As for Miles's suggestion to interpret the magic file directly, I think
it's a bad idea: let's not reinvent the wheel, the code that parses this
database and uses it already exists, it's in libmagic, so we should just
use it.


        Stefan

Re: using libmagic in Emacs?

[Juri Linkov]

>     The problem is that `image-jpeg-p' in image.el refuses to accept
>     non-JFIF JPEG image files whereas Emacs can correctly display them
>     when tests in `image-jpeg-p' are ignored.
>
>     Using libmagic means looking only for 2 bytes 0xffd8 (a magic number
>     of JPEG files) as described by the magic number file:
>
>       0	beshort		0xffd8		JPEG image data
>
>     It seems this is enough to determine JPEG files.  But I'm not confident
>     about removing additional tests from `image-jpeg-p'.  We could keep the
>     current rules in image.el as a fall-back when libmagic is not available.
>
> Whatever we do with the function `image-jpeg-p', we could easily make
> Emacs test these two bytes.  It makes no sense to install code to link
> with libmagic just to handle that and a few other similar things.

The following patch changes `image-type-header-regexps' to test only
two bytes of the JPEG magic number:

Index: lisp/image.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/image.el,v
retrieving revision 1.87
diff -u -r1.87 image.el
--- lisp/image.el	24 Feb 2009 10:29:00 -0000	1.87
+++ lisp/image.el	25 Aug 2009 20:33:16 -0000
@@ -43,7 +43,7 @@
 static \\(unsigned \\)?char \\1_bits" . xbm)
     ("\\`\\(?:MM\0\\*\\|II\\*\0\\)" . tiff)
     ("\\`[\t\n\r ]*%!PS" . postscript)
-    ("\\`\xff\xd8" . (image-jpeg-p . jpeg))
+    ("\\`\xff\xd8" . jpeg)
     (,(let* ((incomment-re "\\(?:[^-]\\|-[^-]\\)")
 	     (comment-re (concat "\\(?:!--" incomment-re "*-->[ \t\r\n]*<\\)")))
 	(concat "\\(?:<\\?xml[ \t\r\n]+[^>]*>\\)?[ \t\r\n]*<"

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Juri Linkov]

>     For instance, Java archive files have the .jar extension but build on
>     the ZIP file format, so they can be visited in Emacs with the help of
>     `archive-mode'.  Enterprise Java archives with the .ear extension
>     and Web application Java archives with the .war extension all are
>     based on the ZIP file format as well as OpenDocument files with
>     extensions .odt .ods .odb .odp .odg .odf, Firefox add-ons (.xpi),
>     Keyhole Markup (.kmz), and many other file types that can be potentially
>     opened in Emacs if were identified as archive files by libmagic.
>
> How hard would it be to change the code in Emacs to recognize these
> using the existing mechanism?

Not hard at all.  For the ZIP file format it's just one line
in `magic-fallback-mode-alist'.  Unlike `image-type-auto-detected-p'
from the preloaded image.el, we can't use `archive-find-type' in
`magic-fallback-mode-alist' because arc-mode.el is not preloaded.
So we have to copy archive magic numbers manually from arc-mode.el
to `magic-fallback-mode-alist'.

Index: lisp/files.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/files.el,v
retrieving revision 1.1069
diff -u -r1.1069 files.el
--- lisp/files.el	17 Aug 2009 23:40:22 -0000	1.1069
+++ lisp/files.el	25 Aug 2009 20:36:28 -0000
@@ -2399,6 +2399,7 @@
 
 (defvar magic-fallback-mode-alist
   `((image-type-auto-detected-p . image-mode)
+    ("\\(PK00\\)?[P]K\003\004" . archive-mode) ; zip
     ;; The < comes before the groups (but the first) to reduce backtracking.
     ;; TODO: UTF-16 <?xml may be preceded by a BOM 0xff 0xfe or 0xfe 0xff.
     ;; We use [ \t\r\n] instead of `\\s ' to make regex overflow less likely.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Thien-Thi Nguyen]

() Miles Bader <miles@gnu.org>
() Tue, 25 Aug 2009 11:19:37 +0900

   If there was such elisp code, Emacs could use any magic rules
   file on the system, and in addition, could distribute it's own
   (perhaps smaller) set.

Some proof-of-concept grade Scheme code that (re)processes the
magic rules format into sexps, and also does the non-char-encoding
side of file(1) is at [0].  Converted rules (v1, v2) are at [1].

(Aside) I think the best candidate for libfoo integration with
Emacs would be libguile.  In contrast, when i read of other
libfoo proposals, i can't help but feel somewhat deflated.

thi

_______________________________________________
[0] http://www.gnuvola.org/software/ttn-do/
    (see file magic.scm in the tarball)
[1] http://www.gnuvola.org/data/index.html
    (see entry "de-uglified magic file")

Language identification (was: using libmagic in Emacs)

[Juri Linkov]

> I often wish that files would open in Emacs with correct mode
> more often when there is no file extension.

In `auto-mode-alist' you can see that with the exception of
`archive-mode', `doc-view-mode' and `image-mode', all remaining
modes are programming text modes.  It would be more useful
to identify file types for these modes that libmagic can't do.
Do you know a library that identifies programming languages?
Such a library might be implemented using a Bayesian classifier
trained on a sufficiently large corpus of different programming
languages.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: Language identification

[Stefan Monnier]

>> I often wish that files would open in Emacs with correct mode
>> more often when there is no file extension.
> In `auto-mode-alist' you can see that with the exception of
> `archive-mode', `doc-view-mode' and `image-mode', all remaining
> modes are programming text modes.  It would be more useful
> to identify file types for these modes that libmagic can't do.
> Do you know a library that identifies programming languages?
> Such a library might be implemented using a Bayesian classifier
> trained on a sufficiently large corpus of different programming
> languages.

OTOH, how often do you see a file containg programming language code and
yet without ny extension?


        Stefan

Re: Language identification

[Alex Ott]

Hello

N-Gram algorithms is could be used to identify languages - it simpler than
bayes, and requires smaller database

Juri Linkov  at "Fri, 28 Aug 2009 03:27:35 +0300" wrote:
 >> I often wish that files would open in Emacs with correct mode
 >> more often when there is no file extension.

 JL> In `auto-mode-alist' you can see that with the exception of
 JL> `archive-mode', `doc-view-mode' and `image-mode', all remaining
 JL> modes are programming text modes.  It would be more useful
 JL> to identify file types for these modes that libmagic can't do.
 JL> Do you know a library that identifies programming languages?
 JL> Such a library might be implemented using a Bayesian classifier
 JL> trained on a sufficiently large corpus of different programming
 JL> languages.



-- 
With best wishes, Alex Ott, MBA
http://alexott.blogspot.com/           http://xtalk.msk.su/~ott/
http://alexott-ru.blogspot.com/

Re: Language identification

[Alex Ott]

Sorry, I skipped, that this was about programming languages, not real
languages.  

Juri Linkov  at "Fri, 28 Aug 2009 03:27:35 +0300" wrote:
 >> I often wish that files would open in Emacs with correct mode
 >> more often when there is no file extension.

 JL> In `auto-mode-alist' you can see that with the exception of
 JL> `archive-mode', `doc-view-mode' and `image-mode', all remaining
 JL> modes are programming text modes.  It would be more useful
 JL> to identify file types for these modes that libmagic can't do.
 JL> Do you know a library that identifies programming languages?
 JL> Such a library might be implemented using a Bayesian classifier
 JL> trained on a sufficiently large corpus of different programming
 JL> languages.



-- 
With best wishes, Alex Ott, MBA
http://alexott.blogspot.com/           http://xtalk.msk.su/~ott/
http://alexott-ru.blogspot.com/

Re: Language identification

[Stephen J. Turnbull]

Stefan Monnier writes:

 > OTOH, how often do you see a file containg programming language code and
 > yet without ny extension?

Extremely frequently.  The great majority that I see are correctly
identified by file(1) (I believe using libmagic), however, by parsing
the shebang.

There are also cases of multiple extensions, where I've seen (for
example) foo.c.inc used for C implementation code that is used in
multiple contexts (perhaps with different behavior according to
#ifdefs).  This would not be recognized by typical Emacs extension
parsing since although it matches something like "\.c\>", it doesn't
match the more usual idioms of "\.c$" or "\.c\'".

Re: Language identification

[Stefan Monnier]

>> OTOH, how often do you see a file containg programming language code and
>> yet without ny extension?
> Extremely frequently.

In what kind of circumstance?

> The great majority that I see are correctly identified by file(1) (I
> believe using libmagic), however, by parsing the shebang.

Oh, so they're executables with a shebang.  That's OK we don't need
`file' for that since we have interpreter-mode-alist.  Emacs should
already DTRT for them.

> There are also cases of multiple extensions, where I've seen (for
> example) foo.c.inc used for C implementation code that is used in
> multiple contexts (perhaps with different behavior according to
> #ifdefs).  This would not be recognized by typical Emacs extension
> parsing since although it matches something like "\.c\>", it doesn't
> match the more usual idioms of "\.c$" or "\.c\'".

I've had

  (setq auto-mode-alist (append auto-mode-alist '(("\\.[^/.]+\\'" ignore t))))

in my .emacs for eons to cover such cases.


        Stefan

Re: Language identification

[Juri Linkov]

>>> In `auto-mode-alist' you can see that with the exception of
>>> `archive-mode', `doc-view-mode' and `image-mode', all remaining
>>> modes are programming text modes.  It would be more useful
>>> to identify file types for these modes that libmagic can't do.
>>> Do you know a library that identifies programming languages?
>>> Such a library might be implemented using a Bayesian classifier
>>> trained on a sufficiently large corpus of different programming
>>> languages.
>>
>> N-Gram algorithms is could be used to identify languages - it simpler
>> than bayes, and requires smaller database
>
> Sorry, I skipped, that this was about programming languages, not real
> languages.

It would be interesting to try using N-Gram algorithms for programming
languages and see how well they perform.  For example, most frequently
used bigram "/*" belongs to C, most frequently used trigram ";;;" belongs
to Lisp, etc.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: Language identification

[Juri Linkov]

>>> I often wish that files would open in Emacs with correct mode
>>> more often when there is no file extension.
>> In `auto-mode-alist' you can see that with the exception of
>> `archive-mode', `doc-view-mode' and `image-mode', all remaining
>> modes are programming text modes.  It would be more useful
>> to identify file types for these modes that libmagic can't do.
>> Do you know a library that identifies programming languages?
>> Such a library might be implemented using a Bayesian classifier
>> trained on a sufficiently large corpus of different programming
>> languages.
>
> OTOH, how often do you see a file containg programming language code and
> yet without ny extension?

More often with a non-standard extension than without any extension.

Also there are conflicting extensions like e.g. ".pl" for both
Perl and Prolog (esp. SWI-Prolog).

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: Language identification

[Richard Stallman]

     > OTOH, how often do you see a file containg programming language code and
     > yet without ny extension?

    Extremely frequently.

Why do these files not identify the language explicitly?  It is easy
to do.

      The great majority that I see are correctly
    identified by file(1) (I believe using libmagic), however, by parsing
    the shebang.

That statement suggests that there are exceptions.  I would expect
there are, because guessing the programming language is an unreliable
solution.

Emacs uses a reliable solution: users should identify the language
either with the file name, or inside the file with a -*- line or a
local variables list.  It takes very little work to make a file say
what its language is, and the result is to identify the language
reliably from then on.

I don't think we should switch from our reliable to solution to
guessing.

Is there a reason why users don't use the existing reliable mechanism?
Is there a real difficulty with using it?

Re: Language identification

[Stefan Monnier]

> Also there are conflicting extensions like e.g. ".pl" for both
> Perl and Prolog (esp. SWI-Prolog).

That's indeed an interesting case, where content-based mode choice might
make sense.  Thanks for reminding me of it.


        Stefan

Re: Language identification

[Stephen J. Turnbull]

Stefan Monnier writes:

 > > The great majority that I see are correctly identified by file(1) (I
 > > believe using libmagic), however, by parsing the shebang.
 > 
 > Oh, so they're executables with a shebang.  That's OK we don't need
 > `file' for that since we have interpreter-mode-alist.  Emacs should
 > already DTRT for them.

Sure.  Maybe there's a better way.  Maybe libmagic is it.  Maybe not.

However, you asked "how often do you see files containing programming
languages without an extension?"  The answer is, it's very common, but
the most common case is Unix command scripts with shebangs, which file
handles just as well as Emacs does.

 > I've had
 > 
 >   (setq auto-mode-alist (append auto-mode-alist '(("\\.[^/.]+\\'" ignore t))))
 > 
 > in my .emacs for eons to cover such cases.

Well, maybe it's time to move it from your .emacs to core emacs?

Re: Language identification

[Stephen J. Turnbull]

Richard Stallman writes:

 > Is there a reason why users don't use the existing reliable mechanism?

Many of the authors don't use Emacs, is my guess.

Re: Language identification

[Chong Yidong]

"Stephen J. Turnbull" <stephen@xemacs.org> writes:

> However, you asked "how often do you see files containing programming
> languages without an extension?"  The answer is, it's very common, but
> the most common case is Unix command scripts with shebangs, which file
> handles just as well as Emacs does.

I guess the question should be, how often do you see such files that
Emacs can't handle as well as libmagic?

Even in such situations, I think the response should be to improve
Emacs' file handling anyway, since libmagic is not available on all
platforms.

Re: Language identification

[Stefan Monnier]

>> Is there a reason why users don't use the existing reliable mechanism?
> Many of the authors don't use Emacs, is my guess.

You mean they're still using `ed'?  Boggles the mind!


        Stefan

Re: Language identification

[Stephen J. Turnbull]

Stefan Monnier writes:

 > >> Is there a reason why users don't use the existing reliable mechanism?
 > > Many of the authors don't use Emacs, is my guess.
 > 
 > You mean they're still using `ed'?  Boggles the mind!

Sure, you could have too, and that probably would have been for the
best.  But freedom to choose is what GNU's all about, and I'm glad you
had the choice (even though you failed to choose ed(1), the Godfather
of editors).

If-my-tongue-were-any-further-in-cheek-it-would-be-in-Mozambique-ly y'rs

Re: Language identification

[Richard Stallman]

    > OTOH, how often do you see a file containg programming language code and
    > yet without ny extension?

    More often with a non-standard extension than without any extension.

So why not rename the files, or put in -*- lines?

    Also there are conflicting extensions like e.g. ".pl" for both
    Perl and Prolog (esp. SWI-Prolog).

Perhaps we should promote .plg for Prolog.

Re: Language identification

[Juri Linkov]

>     > OTOH, how often do you see a file containg programming language code and
>     > yet without ny extension?
>
>     More often with a non-standard extension than without any extension.
>
> So why not rename the files, or put in -*- lines?

Often this is not possible when files are not under my control.

>     Also there are conflicting extensions like e.g. ".pl" for both
>     Perl and Prolog (esp. SWI-Prolog).
>
> Perhaps we should promote .plg for Prolog.

I'd rather prefer to promote changing the Perl file extension since
Prolog is older than Perl :)  But I think neither is realistic.

Currently I use this hack in .emacs to distinguish between Perl and Prolog:

(add-hook 'find-file-hooks
          (lambda ()
            (when (and (looking-at "#") (string-match "Prolog" mode-name))
              (perl-mode))))

since almost all Perl files begin with a comment, even library files
that have no shebangs.

But I agree such guessing is unreliable.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Juri Linkov]

> If some other Lisp code is interested in the mime type of a file,
> there is a much easier way to find it out: run `file'.

I agree that running `file' is a simpler solution.  So I propose
at least the following patch to add content-based MIME-type identification
to one particular function `mailcap-file-default-commands' that needs
this when filename extension-based identification fails:

Index: lisp/gnus/mailcap.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/gnus/mailcap.el,v
retrieving revision 1.26
diff -c -r1.26 mailcap.el
*** lisp/gnus/mailcap.el	5 Jan 2009 03:22:07 -0000	1.26
--- lisp/gnus/mailcap.el	29 Aug 2009 23:18:45 -0000
***************
*** 1030,1037 ****
  	  ;; All unique MIME types from file extensions
  	  (mailcap-delete-duplicates
  	   (mapcar (lambda (file)
! 		     (mailcap-extension-to-mime
! 		      (file-name-extension file t)))
  		   files)))
  	 (all-mime-info
  	  ;; All MIME info lists
--- 1030,1042 ----
  	  ;; All unique MIME types from file extensions
  	  (mailcap-delete-duplicates
  	   (mapcar (lambda (file)
! 		     (or (mailcap-extension-to-mime
! 			  (file-name-extension file t))
! 			 (replace-regexp-in-string
! 			  ".*:\\s-*\\(.*\\)\\s-*" "\\1"
! 			  (shell-command-to-string
! 			   (concat "file --mime "
! 				   (shell-quote-argument file))))))
  		   files)))
  	 (all-mime-info
  	  ;; All MIME info lists

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: Juri Linkov <juri@jurta.org>
> Date: Sun, 30 Aug 2009 02:19:12 +0300
> Cc: monnier@IRO.UMontreal.CA, joakim@verona.se, emacs-devel@gnu.org
> 
> I agree that running `file' is a simpler solution.

PLEASE do not base Emacs infrastructure on external programs, unless
they come with Emacs.  `file' is not available on every platform, and
even on those it is, the quality and extent of its database is unclear
and so cannot be relied upon.

I really don't understand why linking against a simple free library is
an issue, but if it is, we should find a different solution using some
database internal to Emacs, as we did until now.

In any case, invoking external programs without being smart about
their non-existence is not something we should have in Emacs.

Re: Language identification

[Richard Stallman]

    > Also there are conflicting extensions like e.g. ".pl" for both
    > Perl and Prolog (esp. SWI-Prolog).

    That's indeed an interesting case, where content-based mode choice might
    make sense.  Thanks for reminding me of it.

I'd prefer a very specific feature for choosing between these two
languages to use of a general mechanism.  The specific feature
would probably be more reliable, and people would not be tempted
to use it for other issues where it is not the right approach.

But it would be even better to convince people to use distinct
extensions.

Re: using libmagic in Emacs?

[Juri Linkov]

>> I agree that running `file' is a simpler solution.
>
> PLEASE do not base Emacs infrastructure on external programs, unless
> they come with Emacs.

There are many features in Emacs that depend on external programs,
e.g. `ls' for dired, `find' and `grep', `man', `ispell', `shell',
`gdb', `diff', VCS tools, etc.

> `file' is not available on every platform, and even on those it is,

When `libmagic' is available, then usually `file' is available as well
on the same platform.

> the quality and extent of its database is unclear and so cannot be
> relied upon.
>
> I really don't understand why linking against a simple free library is
> an issue, but if it is, we should find a different solution using some
> database internal to Emacs, as we did until now.

If someone thinks adding the magic number database to Emacs is important,
then fine, let's do it.  But this doesn't preclude from using `file'
since we already have many such pairs of external programs and their
emulations for the case when an external program is not available, e.g.
`ls' and ls-lisp, `grep' and multi-occur, `shell' and eshell, etc.

> In any case, invoking external programs without being smart about
> their non-existence is not something we should have in Emacs.

My patch fails gracefully when `file' is not available, I tried
removing `file' without any problem.  The function just returns nil.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: Juri Linkov <juri@jurta.org>
> Cc: emacs-devel@gnu.org,  joakim@verona.se
> Date: Sun, 30 Aug 2009 23:54:34 +0300
> 
> >> I agree that running `file' is a simpler solution.
> >
> > PLEASE do not base Emacs infrastructure on external programs, unless
> > they come with Emacs.
> 
> There are many features in Emacs that depend on external programs,
> e.g. `ls' for dired, `find' and `grep', `man', `ispell', `shell',
> `gdb', `diff', VCS tools, etc.

I said infrastructure, not features.  Of those you mentioned only `ls'
is used in infrastructure, and that's precisely why we had to write
ls-lisp.el.

> > `file' is not available on every platform, and even on those it is,
> 
> When `libmagic' is available, then usually `file' is available as well
> on the same platform.

No.  libmagic can be bundled and compiled with Emacs.  `file' needs to
be present.

> > In any case, invoking external programs without being smart about
> > their non-existence is not something we should have in Emacs.
> 
> My patch fails gracefully when `file' is not available, I tried
> removing `file' without any problem.  The function just returns nil.

And that is graceful how?

Re: Language identification

[Richard Stallman]

    since almost all Perl files begin with a comment, even library files
    that have no shebangs.

What is a "shebang"?

Re: using libmagic in Emacs?

[Richard Stallman]

    PLEASE do not base Emacs infrastructure on external programs, unless
    they come with Emacs.  `file' is not available on every platform, and

libmagic isn't either.

    even on those it is, the quality and extent of its database is unclear
    and so cannot be relied upon.

On systems that have libmagic, isn't it the case that file uses libmagic?

    I really don't understand why linking against a simple free library is
    an issue, but if it is, we should find a different solution using some
    database internal to Emacs, as we did until now.

It shouldn't be a big deal.  Only a few specialized places should want
to run `file' on a file.

Re: Language identification

[Richard Stallman]

    >     Also there are conflicting extensions like e.g. ".pl" for both
    >     Perl and Prolog (esp. SWI-Prolog).
    >
    > Perhaps we should promote .plg for Prolog.

    I'd rather prefer to promote changing the Perl file extension since
    Prolog is older than Perl :)  But I think neither is realistic.

Why so pessimistic?  I'm sure lots of people find this conflict
annoying, and not just Emacs users.  Solving it would help everyone
affected, which mainly means Prolog users, since tools are more likely
to assume Perl.

We should not give up on the best solution without at least proposing
it.

Is anyone here active in the Prolog community?

Re: Language identification

[David Kastrup]

Richard Stallman <rms@gnu.org> writes:

>     since almost all Perl files begin with a comment, even library files
>     that have no shebangs.
>
> What is a "shebang"?

#!

-- 
David Kastrup

Re: Language identification

[Jan D.]

31 aug 2009 kl. 05.32 skrev Richard Stallman <rms@gnu.org>:

>    since almost all Perl files begin with a comment, even library  
> files
>    that have no shebangs.
>
> What is a "shebang"?
>

#!

     Jan D

Re: using libmagic in Emacs?

[Chong Yidong]

Richard Stallman <rms@gnu.org> writes:

>     PLEASE do not base Emacs infrastructure on external programs, unless
>     they come with Emacs.  `file' is not available on every platform, and
>
> libmagic isn't either.
>
>     even on those it is, the quality and extent of its database is unclear
>     and so cannot be relied upon.
>
> On systems that have libmagic, isn't it the case that file uses libmagic?
>
>     I really don't understand why linking against a simple free library is
>     an issue, but if it is, we should find a different solution using some
>     database internal to Emacs, as we did until now.
>
> It shouldn't be a big deal.  Only a few specialized places should want
> to run `file' on a file.

No one has yet explained why we shouldn't deal with such failures by
simply fixing Emacs' file detection, instead of relying on libmagic or
file.  Given that libmagic/file isn't always going to be present, and
there's no intention of removing our file detection code, why not make
sure the latter works?  Are there any situations we are inherently
incapable of detecting, and why?

Re: using libmagic in Emacs?

[Juri Linkov]

>> > PLEASE do not base Emacs infrastructure on external programs, unless
>> > they come with Emacs.
>>
>> There are many features in Emacs that depend on external programs,
>> e.g. `ls' for dired, `find' and `grep', `man', `ispell', `shell',
>> `gdb', `diff', VCS tools, etc.
>
> I said infrastructure, not features.  Of those you mentioned only `ls'
> is used in infrastructure, and that's precisely why we had to write
> ls-lisp.el.

`mailcap-file-default-commands' is not infrastructure.  It's one
small feature.

>> My patch fails gracefully when `file' is not available, I tried
>> removing `file' without any problem.  The function just returns nil.
>
> And that is graceful how?

When it returns nil, then default commands are the same as provided
by mailcap for plain text files, i.e. `less', `konqueror', etc.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Juri Linkov]

> No one has yet explained why we shouldn't deal with such failures by
> simply fixing Emacs' file detection, instead of relying on libmagic or
> file.  Given that libmagic/file isn't always going to be present, and
> there's no intention of removing our file detection code, why not make
> sure the latter works?

Sure, we need to support the existing file detection code for the case
of absent libmagic/file.  This means manually copying necessary parts
of the magic database to `magic-fallback-mode-alist',
`image-type-header-regexps', `archive-find-type'.

> Are there any situations we are inherently incapable of detecting,
> and why?

One situation is when the number of formats to copy from the magic
database is too high, e.g. for all ImageMagick formats.

Also the magic database has simple rules for detecting C, Lisp and
Perl programs, but these rules are unreliable.

Another useful case for libmagic/file is getting MIME types and mailcap
commands to run on them as demonstrated by my patch.  But it seems this
feature is not too important to justify adding libmagic to Emacs instead
of running `file'.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: Juri Linkov <juri@jurta.org>
> Cc: emacs-devel@gnu.org,  joakim@verona.se
> Date: Mon, 31 Aug 2009 19:17:52 +0300
> 
> >> > PLEASE do not base Emacs infrastructure on external programs, unless
> >> > they come with Emacs.
> >>
> >> There are many features in Emacs that depend on external programs,
> >> e.g. `ls' for dired, `find' and `grep', `man', `ispell', `shell',
> >> `gdb', `diff', VCS tools, etc.
> >
> > I said infrastructure, not features.  Of those you mentioned only `ls'
> > is used in infrastructure, and that's precisely why we had to write
> > ls-lisp.el.
> 
> `mailcap-file-default-commands' is not infrastructure.  It's one
> small feature.

A feature is something that stands on its own.  I don't think
`mailcap-file-default-commands' qualifies, nor would any other
function that returns something related to a file's type.  A feature
would _use_ these to actually do something useful with the file.

> >> My patch fails gracefully when `file' is not available, I tried
> >> removing `file' without any problem.  The function just returns nil.
> >
> > And that is graceful how?
> 
> When it returns nil, then default commands are the same as provided
> by mailcap for plain text files, i.e. `less', `konqueror', etc.

Which is clearly un-graceful in my book.

Re: using libmagic in Emacs?

[Richard Stallman]

    > There are many features in Emacs that depend on external programs,
    > e.g. `ls' for dired, `find' and `grep', `man', `ispell', `shell',
    > `gdb', `diff', VCS tools, etc.

    I said infrastructure, not features.

I don't expect any general infrastructure to use `file', just a few
commands.  If those commands have to do their best without `file'
on some systems, it won't be a big deal.

    > When `libmagic' is available, then usually `file' is available as well
    > on the same platform.

    No.  libmagic can be bundled and compiled with Emacs.

I don't think that price is worth paying for the use of libmagic.
It is not important enough.

Re: using libmagic in Emacs?

[Stefan Monnier]

> No one has yet explained why we shouldn't deal with such failures by
> simply fixing Emacs' file detection, instead of relying on libmagic or

Because we don't want to keep reinventing the wheel, do we?


        Stefan

Re: using libmagic in Emacs?

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Mon, 31 Aug 2009 19:47:14 -0400
> Cc: juri@jurta.org, Eli Zaretskii <eliz@gnu.org>, rms@gnu.org, joakim@verona.se,
> 	emacs-devel@gnu.org
> 
> > No one has yet explained why we shouldn't deal with such failures by
> > simply fixing Emacs' file detection, instead of relying on libmagic or
> 
> Because we don't want to keep reinventing the wheel, do we?

What wheel is that?  Emacs has been consulting various internal
databases since time immemoriam.  We do the same with Unicode
databases as well.

Re: using libmagic in Emacs?

[Stefan Monnier]

>> > No one has yet explained why we shouldn't deal with such failures by
>> > simply fixing Emacs' file detection, instead of relying on libmagic or
>> Because we don't want to keep reinventing the wheel, do we?
> What wheel is that?  Emacs has been consulting various internal
> databases since time immemoriam.  We do the same with Unicode
> databases as well.

Yes, Emacs reinvented many wheels, and even preinvented some.
That doesn't make reinvention any more desirable.


        Stefan

Re: using libmagic in Emacs?

[Richard Stallman]

    > It shouldn't be a big deal.  Only a few specialized places should want
    > to run `file' on a file.

    No one has yet explained why we shouldn't deal with such failures by
    simply fixing Emacs' file detection, instead of relying on libmagic or
    file.

I don't think we're talking about the same question.
"Emacs' file type detection" is used inside find-file.
I'm proposing the use of `file' in othehr specific features,
not in find-file.

Re: using libmagic in Emacs?

[Richard Stallman]

    > `mailcap-file-default-commands' is not infrastructure.  It's one
    > small feature.

    A feature is something that stands on its own.  I don't think
    `mailcap-file-default-commands' qualifies, nor would any other
    function that returns something related to a file's type.  A feature
    would _use_ these to actually do something useful with the file.

You're right; but the point is that this is used in very specific
features, not in something general and basic such as find-file.

Re: using libmagic in Emacs?

[Stefan Monnier]

> You're right; but the point is that this is used in very specific
> features, not in something general and basic such as find-file.

My intended use of libmagic is as a sidekick to magic-mode-alist, so
very much used by find-file.


        Stefan

Re: using libmagic in Emacs?

[Richard Stallman]

    > You're right; but the point is that this is used in very specific
    > features, not in something general and basic such as find-file.

    My intended use of libmagic is as a sidekick to magic-mode-alist, so
    very much used by find-file.

Depending on libmagic is too much price to pay for saving a small
amount of work.  It's better to do the small amount of work needed to
recognize the few file types we want to recognize, using the existing
mechanisms.

Re: using libmagic in Emacs?

[Stefan Monnier]

>> You're right; but the point is that this is used in very specific
>> features, not in something general and basic such as find-file.
>     My intended use of libmagic is as a sidekick to magic-mode-alist, so
>     very much used by find-file.
> Depending on libmagic is too much price to pay for saving a small
> amount of work.  It's better to do the small amount of work needed to
> recognize the few file types we want to recognize, using the existing
> mechanisms.

I'd rather let other people do this work.  That's why libmagic
makes a lot of sense.


        Stefan

Re: using libmagic in Emacs?

[Richard Stallman]

    > Depending on libmagic is too much price to pay for saving a small
    > amount of work.  It's better to do the small amount of work needed to
    > recognize the few file types we want to recognize, using the existing
    > mechanisms.

    I'd rather let other people do this work.  That's why libmagic
    makes a lot of sense.

It's a small amount of work, and the burden of distributing and using
libmagic will be a persistant annoyance.