Re: request for review: Doing direct file I/O in Emacs Lisp

[Oliver Scholz]

Stefan Monnier <address@hidden> writes:

>> The following patch implements a file-handle interface for Emacs Lisp,
>> which allows files to be directly opened and read/written to without
>> an intervening buffer.  Eshell can now use this, for example, to
>> greatly speed up output redirection (by several orders of magnitude).
>
> Doesn't seem like a bad idea, but I'd rather postpone it to
> after-the-release.
[...]

FWIW … while working on an RTF reader I found it very annoying that I
have to insert the entire RTF file into a buffer, then tokenize it
character-wise, then delete that parts of the buffer that are
recognized as markup, applying text properties to the remaining text
as appropriate.

Being able to fetch characters from a stream, and deal with them
through several layers of abstraction, and then inserting the actual
text with properties into a buffer would be much nicer and cleaner.

Thus I have a low-level feature request (for after-the-release):
provide an interface to the file visiting routines such that Lisp code
which is meant to deal with formatted text can handle the file’s
content as a character stream (of course this makes sense only if it
is efficient).

For example, add an optional CHARSTREAMP element to the elements of
‘format-alist’. If it is non-nil, FROM-FN and TO-FN get a file handler
as additional argument and take the full responsibility for writing to
the file/inserting the file’s content into the buffer.

    Oliver
-- 
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