[FFmpeg-devel] [PATCH v17 1/5] libavutil: Add wchartoutf8(), wchartoansi(), utf8toansi() and getenv_utf8()

[Martin Storsjö]

On Fri, 17 Jun 2022, Nil Admirari wrote:

> wchartoutf8() converts strings returned by WinAPI into UTF-8,
> which is FFmpeg's preffered encoding.
>
> Some external dependencies, such as AviSynth, are still
> not Unicode-enabled. utf8toansi() converts UTF-8 strings
> into ANSI in two steps: UTF-8 -> wchar_t -> ANSI.
> wchartoansi() is responsible for the second step of the conversion.
> Conversion in just one step is not supported by WinAPI.
>
> Since these character converting functions allocate the buffer
> of necessary size, they also facilitate the removal of MAX_PATH limit
> in places where fixed-size ANSI/WCHAR strings were used
> as filename buffers.
>
> getenv_utf8() wraps _wgetenv() converting its input from
> and its output to UTF-8. Compared to plain getenv(),
> getenv_utf8() requires a cleanup.
>
> Because of that, in places that only test the existence of
> an environment variable or compare its value with a string
> consisting entirely of ASCII characters, the use of plain getenv()
> is still preferred. (libavutil/log.c check_color_terminal()
> is an example of such a place.)
>
> Plain getenv() is also preffered in UNIX-only code,
> such as bktr.c, fbdev_common.c, oss.c in libavdevice
> or af_ladspa.c in libavfilter.
> ---
> configure                  |  1 +
> libavutil/getenv_utf8.h    | 71 ++++++++++++++++++++++++++++++++++++++
> libavutil/wchar_filename.h | 51 +++++++++++++++++++++++++++
> 3 files changed, 123 insertions(+)
> create mode 100644 libavutil/getenv_utf8.h

This looks generally good - as others seem to be ok with this and there 
doesn't seem to be any more objections, I can push this in a while. (I'm 
not familiar with the avisynth bits though, but it seems like there's 
agreement about it.)

> diff --git a/libavutil/getenv_utf8.h b/libavutil/getenv_utf8.h
> new file mode 100644
> index 0000000000..161e3e6202
> --- /dev/null
> +++ b/libavutil/getenv_utf8.h
> @@ -0,0 +1,71 @@
> +#ifndef AVUTIL_GETENV_UTF8_H
> +#define AVUTIL_GETENV_UTF8_H
> +
> +#include <stdlib.h>
> +
> +#include "mem.h"
> +
> +#ifdef HAVE_GETENV

Note that this should be #if HAVE_GETENV - these constants are always 
defined and evaluate to 0 or 1. No need to resend the patchset just for 
that. (I added an explicit #include "config.h" above here too, just to 
make it clearer.)

// Martin