media/base/media_win.cc

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/base/media.h"

#include <windows.h>
#if defined(_WIN32_WINNT_WIN8)
// The Windows 8 SDK defines FACILITY_VISUALCPP in winerror.h.
#undef FACILITY_VISUALCPP
#endif
#include <delayimp.h>

#include "base/file_path.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/native_library.h"
#include "base/path_service.h"

#pragma comment(lib, "delayimp.lib")

namespace media {

enum FFmpegDLLKeys {
  FILE_LIBAVCODEC,   // full path to libavcodec media decoding library.
  FILE_LIBAVFORMAT,  // full path to libavformat media parsing library.
  FILE_LIBAVUTIL,    // full path to libavutil media utility library.
};

// Retrieves the DLLName for the given key.
static const char* GetDLLName(FFmpegDLLKeys dll_key) {
  // TODO(ajwong): Do we want to lock to a specific ffmpeg version?
  switch (dll_key) {
    case FILE_LIBAVCODEC:
      return "avcodec-54.dll";
    case FILE_LIBAVFORMAT:
      return "avformat-54.dll";
    case FILE_LIBAVUTIL:
      return "avutil-51.dll";
    default:
      LOG(DFATAL) << "Invalid DLL key requested: " << dll_key;
      return "";
  }
}

static bool g_media_library_is_initialized = false;

// Attempts to initialize the media library (loading DLLs, DSOs, etc.).
// Returns true if everything was successfully initialized, false otherwise.
bool InitializeMediaLibrary(const FilePath& base_path) {
  if (g_media_library_is_initialized)
    return true;

  // LoadLibraryEx(..., LOAD_WITH_ALTERED_SEARCH_PATH) cannot handle
  // relative path.
  if (!base_path.IsAbsolute())
    return false;

  FFmpegDLLKeys path_keys[] = {
    media::FILE_LIBAVCODEC,
    media::FILE_LIBAVFORMAT,
    media::FILE_LIBAVUTIL
  };
  HMODULE libs[arraysize(path_keys)] = {NULL};

  for (size_t i = 0; i < arraysize(path_keys); ++i) {
    FilePath path = base_path.AppendASCII(GetDLLName(path_keys[i]));

    // Use alternate DLL search path so we don't load dependencies from the
    // system path.  Refer to http://crbug.com/35857
    const wchar_t* cpath = path.value().c_str();
    libs[i] = ::LoadLibraryEx(cpath, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
    if (!libs[i])
      break;
  }

  // Check that we loaded all libraries successfully.  We only need to check the
  // last array element because the loop above will break without initializing
  // it on any prior error.
  bool media_library_is_initialized = (libs[arraysize(libs) - 1] != NULL);

  if (!media_library_is_initialized) {
    // Free any loaded libraries if we weren't successful.
    for (size_t i = 0; i < arraysize(libs) && libs[i] != NULL; ++i) {
      FreeLibrary(libs[i]);
      libs[i] = NULL;  // Just to be safe.
    }
    return false;
  }

  // Workaround for http://crbug.com/110983
  // LoadLibrary() sometimes AV's when called by delay load helper when we
  // call function in ffmpeg for the first time, and we don't know why.
  // Force delay load helper to fix import table here instead.
  // Theoretically, there is no need to call LoadLibrary() before
  // __HrLoadAllImportsForDll(), it will call LoadLibrary() itself, but there
  // is no way to specify LOAD_WITH_ALTERED_SEARCH_PATH when calling
  // __HrLoadAllImportsForDll(). So we do everything in 2 steps -- first call
  // LoadLibraryEx(..., LOAD_WITH_ALTERED_SEARCH_PATH), then call
  // __HrLoadAllImportsForDll(). Overhead is negligible compared to disk
  // access time.
  // Note: in case of error we are not unloading DLL because unload requires
  //       extra resources and should not be necessary; if we ever decide to
  //       unload by calling __FUnloadDelayLoadedDLL() please add /DELAY:UNLOAD
  //       to the linker command line.
  // TODO(enal): remove that code when we find underlying issue. Delay load
  // should work if library is alreday in memory, regardless of permissions...
  for (size_t i = 0; i < arraysize(path_keys); ++i) {
    if (FAILED(::__HrLoadAllImportsForDll(GetDLLName(path_keys[i]))))
      media_library_is_initialized = false;
  }

  g_media_library_is_initialized = media_library_is_initialized;
  return media_library_is_initialized;
}

void InitializeMediaLibraryForTesting() {
  FilePath file_path;
  CHECK(PathService::Get(base::DIR_EXE, &file_path));
  CHECK(InitializeMediaLibrary(file_path));
}

bool IsMediaLibraryInitialized() {
  return g_media_library_is_initialized;
}

}  // namespace media