How does Emacs find the buffer for a file?

How does Emacs find the buffer for a file?

[Kai Großjohann]

When you do C-x C-f /some/file RET, then Emacs runs
insert-file-contents and puts the output in some buffer.  How does
Emacs determine the buffer from the filename?

Here's some background on why I'm asking this strange question:

There is a bug in Tramp, and I don't know how to start tracking it
down.  Tramp allows you to edit remote files.  If you say C-x C-f
/foo RET (editing the local file /foo), and then say C-x C-f
/[user@host]/foo RET (editing a remote file, also named /foo, via
Tramp), then the remote file contents are inserted into the buffer
containing the local file /foo.

Evaling (buffer-file-name) and buffer-file-name in the remote file
returns "/[sm/user@host]/foo".  (The "sm/" part is an optional part
of the Tramp filename syntax, and Tramp inserts a default value there
if it is not given by the user.)

kai
-- 
~/.signature is: umop 3p!sdn    (Frank Nobis)

Re: How does Emacs find the buffer for a file?

[Eli Zaretskii]

On Sat, 15 Jun 2002 Kai.Grossjohann@CS.Uni-Dortmund.DE wrote:

> When you do C-x C-f /some/file RET, then Emacs runs
> insert-file-contents and puts the output in some buffer.  How does
> Emacs determine the buffer from the filename?

See buffer.c:Fget_file_buffer.  It is called by find-file-noselect, a 
subroutine of find-file.

Re: How does Emacs find the buffer for a file?

[Andreas Schwab]

Eli Zaretskii <eliz@is.elta.co.il> writes:

|> On Sat, 15 Jun 2002 Kai.Grossjohann@CS.Uni-Dortmund.DE wrote:
|> 
|> > When you do C-x C-f /some/file RET, then Emacs runs
|> > insert-file-contents and puts the output in some buffer.  How does
|> > Emacs determine the buffer from the filename?
|> 
|> See buffer.c:Fget_file_buffer.  It is called by find-file-noselect, a 
|> subroutine of find-file.

See also create-file-buffer, also called by find-file-noselect, for
creating a new, unique buffer.

Andreas.

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Andreas Schwab, SuSE Labs, schwab@suse.de
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Re: How does Emacs find the buffer for a file?

[Richard Stallman]

    When you do C-x C-f /some/file RET, then Emacs runs
    insert-file-contents and puts the output in some buffer.  How does
    Emacs determine the buffer from the filename?

Actually it creates a buffer and then runs insert-file-contents.  So
this question does not really make sense.  Emacs does not determine a
buffer, it uses the buffer it just created.

The code is in find-file-noselect and find-file-noselect-1.

    There is a bug in Tramp, and I don't know how to start tracking it
    down.  Tramp allows you to edit remote files.  If you say C-x C-f
    /foo RET (editing the local file /foo), and then say C-x C-f
    /[user@host]/foo RET (editing a remote file, also named /foo, via
    Tramp), then the remote file contents are inserted into the buffer
    containing the local file /foo.

Assuming Tramp uses the file-name-handler-alist mechanism, the only
operation that it will handle is insert-file-contents.  That handler
should insert into the current buffer.  It should never try to find
the buffer to use.

Basically, you need to make sure things are working with Tramp more or
less the same way they are working for local files, aside from
fetching the data of course.  A problem like this would tend to come
from a difference where the two paths ought to work the same way.

Re: How does Emacs find the buffer for a file?

[Kai Großjohann]

Kai.Grossjohann@cs.uni-dortmund.de (Kai Großjohann) writes:

> When you do C-x C-f /some/file RET, then Emacs runs
> insert-file-contents and puts the output in some buffer.  How does
> Emacs determine the buffer from the filename?
>
> Here's some background on why I'm asking this strange question:
>
> There is a bug in Tramp,

Ah, the bug has gone in the current version of Tramp (though I don't
know why).

Thanks for your suggestions.

kai
-- 
People mountain, people sea, today no see, tomorrow see.  (from Chinese)