Mail Archives: cygwin/2009/11/06/11:40:05
[forgot to CC to bug-grep before, so I'm resending this, with one more
comment, and leaving out cygwin-specific parts]
Corinna Vinschen wrote:
> On Nov 6 16:00, Thomas Wolff wrote:
>
>>> ...
>>>
>> I extended your test program to demonstrate the inefficiency of the
>> standard mbrtowc function. [...]
>>
I later had to correct:
> Anyway, corrected results are still by a factor of 3 to 4 in favor of
> my algorithm.
Corinna wrote:
> That's sort of an unfair test. Your utftouni function doesn't care for
> mbstate, error, and surrogate pair handling.
>
This is a question of use cases:
* mbstate is needed e.g. if you feed results of read() which possibly
come in arbitrary chunks directly into mbtowc(); it's not needed if you
only transform complete lines of text at once. The stdlib function is a
little bit too generic (and thus complicated, too) for many applications.
* error handling is there, in my function; it's simplified, incorrect
sequences are all mapped to 0 for the test case but they could as well
return an error indication without performance impact.
* surrogate pair handling is only needed if you pass the string from/to
the Windows API. It's not needed for POSIX applications (provided
wchar_t would be sufficiently wide). So if wchar_t can be extended in
the newlib API, it might be useful to have two implementations; one for
applications (w/o surrogates), one for cygwin itself.
[...]
My main point was that, depending on the use case, some applications
would be better off using less generic, optimized functions.
The kind of dogmatic suggestion (as seen in the "locale scene") that
everybody should use the stdlib wide character functions is often
misleading.
grep and sed would certainly be well advised to change that.
Thomas
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