media/audio/win/avrt_wrapper_win.cc

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/audio/win/avrt_wrapper_win.h"
   6
   7 #include "base/logging.h"
   8
   9 namespace avrt {
  10
  11 // Function pointers
  12 typedef BOOL (WINAPI *AvRevertMmThreadCharacteristicsFn)(HANDLE);
  13 typedef HANDLE (WINAPI *AvSetMmThreadCharacteristicsFn)(LPCWSTR, LPDWORD);
  14 typedef BOOL (WINAPI *AvSetMmThreadPriorityFn)(HANDLE, AVRT_PRIORITY);
  15
  16 HMODULE g_avrt = NULL;
  17 AvRevertMmThreadCharacteristicsFn g_revert_mm_thread_characteristics = NULL;
  18 AvSetMmThreadCharacteristicsFn g_set_mm_thread_characteristics = NULL;
  19 AvSetMmThreadPriorityFn g_set_mm_thread_priority = NULL;
  20
  21 bool Initialize() {
  22   if (!g_set_mm_thread_priority) {
  23     // The avrt.dll is available on Windows Vista and later.
  24     wchar_t path[MAX_PATH] = {0};
  25     ExpandEnvironmentStrings(L"%WINDIR%\\system32\\avrt.dll", path,
  26         arraysize(path));
  27     g_avrt = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
  28     if (!g_avrt)
  29       return false;
  30
  31     g_revert_mm_thread_characteristics =
  32         reinterpret_cast<AvRevertMmThreadCharacteristicsFn>(
  33             GetProcAddress(g_avrt, "AvRevertMmThreadCharacteristics"));
  34     g_set_mm_thread_characteristics =
  35         reinterpret_cast<AvSetMmThreadCharacteristicsFn>(
  36             GetProcAddress(g_avrt, "AvSetMmThreadCharacteristicsW"));
  37     g_set_mm_thread_priority = reinterpret_cast<AvSetMmThreadPriorityFn>(
  38         GetProcAddress(g_avrt, "AvSetMmThreadPriority"));
  39   }
  40
  41   return (g_avrt && g_revert_mm_thread_characteristics &&
  42           g_set_mm_thread_characteristics && g_set_mm_thread_priority);
  43 }
  44
  45 bool AvRevertMmThreadCharacteristics(HANDLE avrt_handle) {
  46   DCHECK(g_revert_mm_thread_characteristics);
  47   return (g_revert_mm_thread_characteristics &&
  48           g_revert_mm_thread_characteristics(avrt_handle));
  49 }
  50
  51 HANDLE AvSetMmThreadCharacteristics(const wchar_t* task_name,
  52                                     DWORD* task_index) {
  53   DCHECK(g_set_mm_thread_characteristics);
  54   return (g_set_mm_thread_characteristics ?
  55           g_set_mm_thread_characteristics(task_name, task_index) : NULL);
  56 }
  57
  58 bool AvSetMmThreadPriority(HANDLE avrt_handle, AVRT_PRIORITY priority) {
  59   DCHECK(g_set_mm_thread_priority);
  60   return (g_set_mm_thread_priority &&
  61           g_set_mm_thread_priority(avrt_handle, priority));
  62 }
  63
  64 }  // namespace avrt