From 284830e5ef2e6fb1ccb83f24bcd3b17fe6375227 Mon Sep 17 00:00:00 2001
From: Cameron Kaiser <classilla@floodgap.com>
Date: Fri, 15 Mar 2019 23:20:18 -0700
Subject: [PATCH] Olga's basic libav framework (#550)

---
 .../platforms/ffmpeg/FFmpegRuntimeLinker.cpp  | 54 +++++++++++++++++++
 .../platforms/ffmpeg/FFmpegRuntimeLinker.h    |  4 ++
 2 files changed, 58 insertions(+)

diff --git a/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp b/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
index f38c35a1c..0f442b5b5 100644
--- a/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
+++ b/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
@@ -10,6 +10,12 @@
 #include "mozilla/Preferences.h"
 #include "prlink.h"
 
+#ifdef XP_DARWIN
+  #include <dlfcn.h>
+  #include <libgen.h>
+  #include <mach-o/dyld.h>
+#endif /* XP_DARWIN */
+
 namespace mozilla
 {
 
@@ -40,7 +46,11 @@ static const char* sLibs[] = {
 #endif
 };
 
+#ifdef XP_DARWIN
+void* FFmpegRuntimeLinker::sLinkedLib = nullptr;
+#else
 PRLibrary* FFmpegRuntimeLinker::sLinkedLib = nullptr;
+#endif /* XP_DARWIN */
 const char* FFmpegRuntimeLinker::sLib = nullptr;
 static unsigned (*avcodec_version)() = nullptr;
 
@@ -60,12 +70,36 @@ FFmpegRuntimeLinker::Link()
 
   MOZ_ASSERT(NS_IsMainThread());
 
+#ifdef XP_DARWIN // Explanation below.
+  char execPath[PATH_MAX];
+  execPath[0] = '\0';
+  uint32_t pathlen = PATH_MAX;
+  _NSGetExecutablePath(execPath, &pathlen);
+  char *execDir = dirname(execPath);
+#endif /* XP_DARWIN */
+
   for (size_t i = 0; i < ArrayLength(sLibs); i++) {
     const char* lib = sLibs[i];
+#ifdef XP_DARWIN
+    /* Loading FFMPEG on Mac OS X (macOS is a typo) fails because mozilla
+      searches for sybols defined in libavutil with a handle to libavcodec.
+      This is due to the fact that NSPR uses NSAddressOfSymbol & cie who limits
+      its researches only to libavcodec and not its dependencies.  We don't have
+      this issue with dlsym().  */
+    if (!(sLinkedLib = dlopen(lib, RTLD_NOW | RTLD_LOCAL))) {
+      /* Bonus time: if we don't find libavcodec in standard locations, we look
+        if our venerable FFMPEG's libraries are in the same folder as XUL. */
+      char *libFullPath = NULL;
+      if (asprintf(&libFullPath, "%s/%s", execDir, lib) > 0 && libFullPath)
+        sLinkedLib = dlopen(libFullPath, RTLD_NOW | RTLD_LOCAL);
+      free(libFullPath);
+    }
+#else
     PRLibSpec lspec;
     lspec.type = PR_LibSpec_Pathname;
     lspec.value.pathname = lib;
     sLinkedLib = PR_LoadLibraryWithFlags(lspec, PR_LD_NOW | PR_LD_LOCAL);
+#endif /* XP_DARWIN */
     if (sLinkedLib) {
       if (Bind(lib)) {
         sLib = lib;
@@ -92,7 +126,11 @@ FFmpegRuntimeLinker::Link()
 /* static */ bool
 FFmpegRuntimeLinker::Bind(const char* aLibName)
 {
+#ifdef XP_DARWIN
+  avcodec_version = (typeof(avcodec_version))dlsym(sLinkedLib,
+#else
   avcodec_version = (typeof(avcodec_version))PR_FindSymbol(sLinkedLib,
+#endif /* XP_DARWIN */
                                                            "avcodec_version");
   uint32_t fullVersion, major, minor, micro;
   fullVersion = GetVersion(major, minor, micro);
@@ -139,6 +177,17 @@ FFmpegRuntimeLinker::Bind(const char* aLibName)
   }
 
 #define LIBAVCODEC_ALLVERSION
+#ifdef XP_DARWIN
+#define AV_FUNC(func, ver)                                                     \
+  if ((ver) & version) {                                                       \
+    if (!(func = (typeof(func))dlsym(sLinkedLib, #func))) {                    \
+      FFMPEG_LOG("Couldn't load function " #func " from %s.", aLibName);       \
+      return false;                                                            \
+    }                                                                          \
+  } else {                                                                     \
+    func = (typeof(func))nullptr;                                              \
+  }
+#else
 #define AV_FUNC(func, ver)                                                     \
   if ((ver) & version) {                                                       \
     if (!(func = (typeof(func))PR_FindSymbol(sLinkedLib, #func))) {            \
@@ -148,6 +197,7 @@ FFmpegRuntimeLinker::Bind(const char* aLibName)
   } else {                                                                     \
     func = (typeof(func))nullptr;                                              \
   }
+#endif /* XP_DARWIN */
 #include "FFmpegFunctionList.h"
 #undef AV_FUNC
 #undef LIBAVCODEC_ALLVERSION
@@ -181,7 +231,11 @@ FFmpegRuntimeLinker::CreateDecoderModule()
 FFmpegRuntimeLinker::Unlink()
 {
   if (sLinkedLib) {
+#ifdef XP_DARWIN
+    dlclose(sLinkedLib);
+#else
     PR_UnloadLibrary(sLinkedLib);
+#endif /* XP_DARWIN */
     sLinkedLib = nullptr;
     sLib = nullptr;
     sLinkStatus = LinkStatus_INIT;
diff --git a/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.h b/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.h
index 05ee8a874..6b7324908 100644
--- a/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.h
+++ b/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.h
@@ -40,7 +40,11 @@ public:
   static uint32_t GetVersion(uint32_t& aMajor, uint32_t& aMinor, uint32_t& aMicro);
 
 private:
+#ifdef XP_DARWIN
+  static void* sLinkedLib;
+#else
   static PRLibrary* sLinkedLib;
+#endif /* XP_DARWIN */
   static const char* sLib;
 
   static bool Bind(const char* aLibName);