opening portions of large file

opening portions of large file

[Sébastien Kirche]

Hi,

i have  googled a bit  but i have  found no reference regarding  the partial
opening of large files (read: without loading the whole file in memory).

I know that for a while Emacs 21.3  (? at least CVS version) has no more the
128 MB  limitation about buffer size.  But what about opening  a large file,
say several hundreds of megabytes ? 

I suppose  that if the file  size exceeds the  main memory it will  cause at
best lots of memory swapping and must be quite slow.

Is there any  mode designed to load a large file  by chunks corresponding to
the displayed buffer (à la UltraEdit-32 in the Windows world) ?

Regards.

-- 
Sébastien Kirche

Re: opening portions of large file

[drkm]

Sébastien Kirche <sebastien.kirche.no@spam.free.fr.invalid> writes:

> Is there any  mode designed to load a large file  by chunks corresponding to
> the displayed buffer (à la UltraEdit-32 in the Windows world) ?

  If you just want to open a specific region of a file, it's easy to
write a command to read the filename and the region bounds, an call
`dd(1)' to extract this region into an temporary file, an add
buffer-locally a generated function to `after-save-hook' to use
`dd(1)' to reinject the temporary file in the initial file.

  If you want to Emacs decides automatically to use such a technique
depending of the file size, determining itself the chunks size,
displays the size in a transparent way (so the user never see he or
she are editing chunks), guarantees tools like Font Lock, Semantic or
nXML validation code to works well, ..., it's, well, IMHO, a quite
more difficult.

--drkm

Re: opening portions of large file

[Sébastien Kirche]

Le 15 Mar 2005, drkm vraute :

> If you want to Emacs decides automatically to use such a technique
> depending of the file size, determining itself the chunks size,
> displays the size in a transparent way (so the user never see he or
> she are editing chunks), guarantees tools like Font Lock, Semantic or
> nXML validation code to works well, ..., it's, well, IMHO, a quite
> more difficult.

Ok.
 
> --drkm

Weird, that remembers me someone... but who ? ;)

-- 
Sébastien Kirche

Re: opening portions of large file

[Thien-Thi Nguyen]

drkm <usenet@fgeorges.org> writes:

> it's, well, IMHO, a quite
> more difficult.

the general solution is "database-mediated" i/o, which is indeed more
difficult, but not out of reach.  once EDB turns the corner to fully (or
at least, "maximally w/in reason") declarative schema design, file slice
editing will fall out of the mix for free.  for now, there is bindat.el
and forms.el (building on these is basically where EDB is heading) to
ri{p,ff} off...

thi