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Re: [HELP] (bug?) Saving a buffer without any conversion?
From: |
Kenichi Handa |
Subject: |
Re: [HELP] (bug?) Saving a buffer without any conversion? |
Date: |
Wed, 15 Jan 2003 10:16:45 +0900 (JST) |
In article <address@hidden>, Mario Lang <address@hidden> writes:
> We're receiving binary content via a network process. After the
> transfer is complete, this buffer should be saved to a file.
> The effect I'm having is that we receive 1372422 bytes via the process
> filter function STRING argument, and after insertion into a buffer,
> we have a buffer with buffer-size 1372422, but after calling (save-buffer)
> we get this:
> -rw-r--r-- 1 root root 1865264 Jan 13 18:35 blah28.mp3
> I'm using:
> (set-process-coding-system proc 'binary 'binary)
> (set-buffer-file-coding-system 'no-conversion t)
address@hidden (Kim F. Storm) writes:
> I have looked at Mario's data before sending it to emacs and after
> emacs has written it to a file.
> It seems that every byte in the range 0xa0 .. 0xff that were in the
> original file is prefixed with an 0x81 byte in the file containing the
> received data. To me, that looks like the internal multi-byte
> representation for the binary data.
No. 0x81 means that 0xA0..0xFF are decoded as Latin-1
chars. That's why raw-text and no-conversion write out 0x81
as is to a file. And that means that somehow:
(set-process-coding-system proc 'binary 'binary)
didn't take effect. When did you execute this function? It
should be before accepting any data from the process
(usually just after start-process or open-network-stream).
I tried the follwoing code and the written file "temp" was
the same as "temp.png".
(defun temp-sentinel (proc str)
(if (string= str "finished\n")
(save-excursion
(set-buffer (process-buffer proc))
(write-file "~/temp"))))
(let (proc)
(save-excursion
(set-buffer (get-buffer-create "temp"))
(set-buffer-file-coding-system 'binary)
(erase-buffer))
(setq proc (start-process "cat" "temp" "cat" "/home/handa/temp.png"))
(set-process-sentinel proc 'temp-sentinel)
(set-process-coding-system proc 'binary 'binary))
Eli Zaretskii <address@hidden> writes:
>> It seems that every byte in the range 0xa0 .. 0xff that were in the
>> original file is prefixed with an 0x81 byte in the file containing the
>> received data. To me, that looks like the internal multi-byte
>> representation for the binary data.
> Yes. That's what no-conversion does: it prevents encoding of the
> internal buffer's contents.
> I suggest to use raw-text for both coding systems above, and see if that
> helps.
The difference of no-conversion and raw-text is only in
handling of EOL format. He should surely use no-conversion
because raw-text will convert both CRLF and LF into LF.
> An alternative approach is to (set-buffer-multibyte nil) before reading
> the data into it and before saving it.
Yes. For instance, by slightly modifying the above code as below:
(let (proc)
(save-excursion
(set-buffer (get-buffer-create "temp"))
(set-buffer-file-coding-system 'binary)
(erase-buffer)
(set-buffer-multibyte nil))
(setq proc (start-process "cat" "temp" "cat" "/home/handa/temp.png"))
(set-process-sentinel proc 'temp-sentinel)
(set-process-coding-system proc 'binary 'binary))
we get the same result more efficiently.
>> The buffer's coding system for save is no-conversion. How did
>> that internal data end up in the file?
> Probably because the buffer was a multibyte buffer, in which case
> no-conversion writes out the internal representation. That's why I
> suggested using raw-text to save the buffer.
Please note that the internal representation for raw-bytes
(eight-bit-control and eight-bit-graphic) are never exposed
in a file even by no-conversion. As I wrote above, 0x81 is
not a leading-byte for raw-bytes but for Latin-1.
---
Ken'ichi HANDA
address@hidden
- [HELP] (bug?) Saving a buffer without any conversion?, Mario Lang, 2003/01/13
- Re: [HELP] (bug?) Saving a buffer without any conversion?,
Kenichi Handa <=
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Kim F. Storm, 2003/01/15
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Kenichi Handa, 2003/01/15
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Kim F. Storm, 2003/01/15
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Eli Zaretskii, 2003/01/15
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Kim F. Storm, 2003/01/16
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Kenichi Handa, 2003/01/16
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Kenichi Handa, 2003/01/15
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Richard Stallman, 2003/01/17
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Kenichi Handa, 2003/01/17
- Re: [HELP] (bug?) Saving a buffer without any conversion?, Mario Lang, 2003/01/15