[FFmpeg-devel] [PATCH v14 4/5] libavformat: Remove MAX_PATH limit and use UTF-8 version of getenv()

[Soft Works]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Hendrik Leppkes
> Sent: Monday, June 13, 2022 8:55 PM
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH v14 4/5] libavformat: Remove
> MAX_PATH limit and use UTF-8 version of getenv()
> 
> On Mon, Jun 13, 2022 at 7:47 PM Soft Works <softworkz at hotmail.com>
> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Nil
> > > Admirari
> > > Sent: Monday, June 13, 2022 6:26 PM
> > > To: ffmpeg-devel at ffmpeg.org
> > > Subject: [FFmpeg-devel] [PATCH v14 4/5] libavformat: Remove
> MAX_PATH
> > > limit and use UTF-8 version of getenv()
> > >
> > > 1. getenv() is replaced with getenv_utf8() across libavformat.
> > > 2. New versions of AviSynth+ are now called with UTF-8 filenames.
> > > 3. Old versions of AviSynth are still using ANSI strings,
> > >    but MAX_PATH limit on filename is removed.
> > > ---
> > >  libavformat/avisynth.c    | 39 +++++++++++++++++++++++++++------
> ----
> > > --
> > >  libavformat/http.c        | 20 +++++++++++++-------
> > >  libavformat/ipfsgateway.c | 35 +++++++++++++++++++++++----------
> --
> > >  libavformat/tls.c         | 11 +++++++++--
> > >  4 files changed, 72 insertions(+), 33 deletions(-)
> > >
> > > diff --git a/libavformat/avisynth.c b/libavformat/avisynth.c
> > > index 8ba2bdead2..a97d12b6b6 100644
> > > --- a/libavformat/avisynth.c
> > > +++ b/libavformat/avisynth.c
> > > @@ -34,6 +34,7 @@
> > >  /* Platform-specific directives. */
> > >  #ifdef _WIN32
> > >    #include "compat/w32dlfcn.h"
> > > +  #include "libavutil/wchar_filename.h"
> > >    #undef EXTERN_C
> > >    #define AVISYNTH_LIB "avisynth"
> > >  #else
> > > @@ -56,6 +57,7 @@ typedef struct AviSynthLibrary {
> > >  #define AVSC_DECLARE_FUNC(name) name ## _func name
> > >      AVSC_DECLARE_FUNC(avs_bit_blt);
> > >      AVSC_DECLARE_FUNC(avs_clip_get_error);
> > > +    AVSC_DECLARE_FUNC(avs_check_version);
> > >      AVSC_DECLARE_FUNC(avs_create_script_environment);
> > >      AVSC_DECLARE_FUNC(avs_delete_script_environment);
> > >      AVSC_DECLARE_FUNC(avs_get_audio);
> > > @@ -137,6 +139,7 @@ static av_cold int
> avisynth_load_library(void)
> > >
> > >      LOAD_AVS_FUNC(avs_bit_blt, 0);
> > >      LOAD_AVS_FUNC(avs_clip_get_error, 0);
> > > +    LOAD_AVS_FUNC(avs_check_version, 0);
> > >      LOAD_AVS_FUNC(avs_create_script_environment, 0);
> > >      LOAD_AVS_FUNC(avs_delete_script_environment, 0);
> > >      LOAD_AVS_FUNC(avs_get_audio, 0);
> > > @@ -807,26 +810,38 @@ static int
> > > avisynth_create_stream(AVFormatContext *s)
> > >  static int avisynth_open_file(AVFormatContext *s)
> > >  {
> > >      AviSynthContext *avs = s->priv_data;
> > > -    AVS_Value arg, val;
> > > +    AVS_Value val;
> > >      int ret;
> > > -#ifdef _WIN32
> > > -    char filename_ansi[MAX_PATH * 4];
> > > -    wchar_t filename_wc[MAX_PATH * 4];
> > > -#endif
> > >
> > >      if (ret = avisynth_context_create(s))
> > >          return ret;
> > >
> > > +    if (!avs_library.avs_check_version(avs->env, 7)) {
> >
> > I like the version check. I don't know about all the derivatives
> > of AviSynth, but I assume you have checked that it's valid for
> > the common ones (or at least the original non-Plus variant)?
> >
> > > +        AVS_Value args[] = {
> > > +            avs_new_value_string(s->url),
> > > +            avs_new_value_bool(1) // filename is in UTF-8
> > > +        };
> > > +        val = avs_library.avs_invoke(avs->env, "Import",
> > > +                                     avs_new_value_array(args,
> 2),
> > > 0);
> > > +    } else {
> > > +        AVS_Value arg;
> > >  #ifdef _WIN32
> > > -    /* Convert UTF-8 to ANSI code page */
> > > -    MultiByteToWideChar(CP_UTF8, 0, s->url, -1, filename_wc,
> > > MAX_PATH * 4);
> > > -    WideCharToMultiByte(CP_THREAD_ACP, 0, filename_wc, -1,
> > > filename_ansi,
> > > -                        MAX_PATH * 4, NULL, NULL);
> > > -    arg = avs_new_value_string(filename_ansi);
> > > +        char *filename_ansi;
> > > +        /* Convert UTF-8 to ANSI code page */
> > > +        if (utf8toansi(s->url, &filename_ansi)) {
> >
> > Two ideas came to my mind how this could be done better.
> > What's actually needed here is not a string conversion, we need
> > a valid and usable filename, and the function could be more
> > something like "get_ansi_filename()".
> >
> > The first thing that this function could do is to convert the
> > the filename to ANSI and right back to UTF-8, then compare the
> > UTF-8 result with the original UTF-8 string. When both are equal,
> > we know that the conversion is safe, otherwise we know that it
> > won't work.
> >
> > Then, we can use the win32 API GetShortFileName(). Which returns
> > file and directory names in 8.3 notation which (IIRC) contains
> > only letters which are valid in the ANSI code page.
> >
> 
> This seems unrelated to this patch, which is about removing the
> MAX_PATH limit. The code previously converted UTF-8 to ANSI, and
> still
> does so now, just without the MAX_PATH limit.
> Further improvements tangential to this topic can, and should, be
> applied independently, and not hold up this patch in discussion-hell
> for longer than necessary.

It was meant as a suggestion not as an objection. I'm fine with this
patch, just to be clear.

softworkz