[FFmpeg-devel] [PATCH v20 1/5] libavutil: Add wchartoutf8(), wchartoansi(), utf8toansi(), getenv_utf8(), freeenv_utf8() and getenv_dup()

[Martin Storsjö]

On Mon, 20 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.
>
> On Windows, getenv_utf8() wraps _wgetenv() converting its input from
> and its output to UTF-8. Strings returned by getenv_utf8()
> must be freed by freeenv_utf8().
>
> On all other platforms getenv_utf8() is a wrapper around getenv(),
> and freeenv_utf8() is a no-op.
>
> The value returned by plain getenv() cannot be modified;
> av_strdup() is usually used when modifications are required.
> However, on Windows, av_strdup() after getenv_utf8() leads to
> unnecessary allocation. getenv_dup() is introduced to avoid
> such an allocation. Value returned by getenv_dup() must be freed
> by av_free().
>
> Because of cleanup complexities, 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    | 86 ++++++++++++++++++++++++++++++++++++++
> libavutil/wchar_filename.h | 53 +++++++++++++++++++++++
> 3 files changed, 140 insertions(+)
> create mode 100644 libavutil/getenv_utf8.h

This set looks good to me, thanks! Will push tomorrow if there's nothing 
more to add on it.

// Martin