Re: [FFmpeg-devel] [PATCH v3 2/2] libavformat/vapoursynth: Update to API version 4, load library at runtime

[Ramiro Polla <ramiro.polla@gmail.com>]

On 2024-07-23 16:59, Stefan Oltmanns via ffmpeg-devel wrote:
> This is the second part for loading the library at runtime, changes
> compared to previous patch revisions:
> 
> -No atexit anymore
> -No global states anymore
> -Moved the registry read for Windows from a separate function inside the
> function to load the dynamic library and simplified it, reducing the
> amount windows-specific code.
> 
> Tested with 2 VapourSynth inputs on these platforms, no problems and
> clean exit:
> 
> -Linux x86_64 (Ubuntu 22.04)
> -Windows 10 x86_64
> -macOS 14 aarch64

> From 6a8e8b7d5bfcfb8eb3cb24ea1f7e14ca117882c4 Mon Sep 17 00:00:00 2001
> From: Stefan Oltmanns <stefan-oltmanns@gmx.net>
> Date: Tue, 23 Jul 2024 16:19:46 +0200
> Subject: [PATCH 2/2] avformat/vapoursynth: load library at runtime
> 
> Signed-off-by: Stefan Oltmanns <stefan-oltmanns@gmx.net>
> ---
>  configure                 |  2 +-
>  libavformat/vapoursynth.c | 65 +++++++++++++++++++++++++++++++++++++--
>  2 files changed, 64 insertions(+), 3 deletions(-)
> 
> diff --git a/configure b/configure
> index c50b5ad4b4..1b6670505a 100755
> --- a/configure
> +++ b/configure
> @@ -7085,7 +7085,7 @@ enabled rkmpp             && { require_pkg_config rkmpp rockchip_mpp  rockchip/r
>                                 { enabled libdrm ||
>                                   die "ERROR: rkmpp requires --enable-libdrm"; }
>                               }
> -enabled vapoursynth       && require_pkg_config vapoursynth "vapoursynth-script >= 55" VSScript4.h getVSScriptAPI
> +enabled vapoursynth       && require_headers "vapoursynth/VSScript4.h vapoursynth/VapourSynth4.h"
>  
>  
>  if enabled gcrypt; then
> diff --git a/libavformat/vapoursynth.c b/libavformat/vapoursynth.c
> index ce15f68180..ad1d6eac61 100644
> --- a/libavformat/vapoursynth.c
> +++ b/libavformat/vapoursynth.c
> @@ -25,7 +25,7 @@
>  
>  #include <limits.h>
>  
> -#include <VSScript4.h>
> +#include <vapoursynth/VSScript4.h>
>  
>  #include "libavutil/avassert.h"
>  #include "libavutil/avstring.h"
> @@ -39,11 +39,26 @@
>  #include "demux.h"
>  #include "internal.h"
>  
> +/* Platform-specific directives. */
> +#ifdef _WIN32
> +  #include <windows.h>
> +  #include "compat/w32dlfcn.h"
> +  #include "libavutil/wchar_filename.h"
> +  #undef EXTERN_C
> +  #define VSSCRIPT_LIB "VSScript.dll"
> +#else
> +  #include <dlfcn.h>
> +  #define VSSCRIPT_NAME "libvapoursynth-script"
> +  #define VSSCRIPT_LIB VSSCRIPT_NAME SLIBSUF
> +#endif
> +
>  struct VSState {
>      const VSSCRIPTAPI *vssapi;
>      VSScript *vss;
>  };
>  
> +typedef const VSSCRIPTAPI *(*VSScriptGetAPIFunc)(int version);
> +
>  typedef struct VSContext {
>      const AVClass *class;
>  
> @@ -51,6 +66,7 @@ typedef struct VSContext {
>  
>      const VSSCRIPTAPI *vssapi;
>      const VSAPI *vsapi;
> +    void *vslibrary;
>  
>      VSNode *outnode;
>      int is_cfr;
> @@ -70,6 +86,40 @@ static const AVOption options[] = {
>      {NULL}
>  };
>  
> +static av_cold void* vs_load_library(VSScriptGetAPIFunc *get_vssapi)
> +{
> +    void *vslibrary = NULL;
> +#ifdef _WIN32
> +    const HKEY hkeys[] = {HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE};
> +    LONG r;
> +    WCHAR vss_path[512];
> +    DWORD buf_size = sizeof(vss_path) - 2;
> +    char *vss_path_utf8;
> +    int i;
> +
> +    for (i = 0; i < sizeof(hkeys); i++) {

FF_ARRAY_ELEMS(hkeys)

> +        if ((r = RegGetValueW(hkeys[i], L"SOFTWARE\\VapourSynth",
> +                      L"VSScriptDLL", RRF_RT_REG_SZ, NULL,
> +                      &vss_path, &buf_size)) == ERROR_SUCCESS)
> +            break;
> +    }
> +    if (r == ERROR_SUCCESS && wchartoutf8(vss_path, &vss_path_utf8) == 0) {
> +        vslibrary = dlopen(vss_path_utf8, RTLD_NOW | RTLD_GLOBAL);

I think calling win32_dlopen() with a full path will be problematic for 
systems without KB2533623. win32_dlopen() might need to be fixed in a 
separate patch.

[...]

Regards,
Ramiro
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