system_wrappers/source/condition_variable_native_win.cc

/*
 *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "webrtc/system_wrappers/interface/trace.h"
#include "webrtc/system_wrappers/source/condition_variable_native_win.h"
#include "webrtc/system_wrappers/source/critical_section_win.h"

namespace webrtc {

static HMODULE library = NULL;
static bool win_support_condition_variables_primitive = false;

PInitializeConditionVariable  PInitializeConditionVariable_;
PSleepConditionVariableCS     PSleepConditionVariableCS_;
PWakeConditionVariable        PWakeConditionVariable_;
PWakeAllConditionVariable     PWakeAllConditionVariable_;

typedef void (WINAPI *PInitializeConditionVariable)(PCONDITION_VARIABLE);
typedef BOOL (WINAPI *PSleepConditionVariableCS)(PCONDITION_VARIABLE,
                                                 PCRITICAL_SECTION, DWORD);
typedef void (WINAPI *PWakeConditionVariable)(PCONDITION_VARIABLE);
typedef void (WINAPI *PWakeAllConditionVariable)(PCONDITION_VARIABLE);

ConditionVariableNativeWin::ConditionVariableNativeWin() {
}

ConditionVariableNativeWin::~ConditionVariableNativeWin() {
}

ConditionVariableWrapper* ConditionVariableNativeWin::Create() {
  ConditionVariableNativeWin* ret_val = new ConditionVariableNativeWin();
  if (!ret_val->Init()) {
    delete ret_val;
    return NULL;
  }
  return ret_val;
}

bool ConditionVariableNativeWin::Init() {
  if (!library) {
    // Native implementation is supported on Vista+.
    library = LoadLibrary(TEXT("Kernel32.dll"));
    // TODO(henrike): this code results in an attempt to load the above dll
    // every time the previous attempt failed. Only try to load once.
    if (library) {
      // TODO(henrike): not thread safe as reading and writing to library is not
      // serialized. Fix.
      WEBRTC_TRACE(kTraceStateInfo, kTraceUtility, -1, "Loaded Kernel.dll");

      PInitializeConditionVariable_ =
          (PInitializeConditionVariable) GetProcAddress(
              library, "InitializeConditionVariable");
      PSleepConditionVariableCS_ = (PSleepConditionVariableCS) GetProcAddress(
          library, "SleepConditionVariableCS");
      PWakeConditionVariable_ = (PWakeConditionVariable) GetProcAddress(
          library, "WakeConditionVariable");
      PWakeAllConditionVariable_ = (PWakeAllConditionVariable) GetProcAddress(
          library, "WakeAllConditionVariable");

      if (PInitializeConditionVariable_ && PSleepConditionVariableCS_
          && PWakeConditionVariable_ && PWakeAllConditionVariable_) {
        WEBRTC_TRACE(
            kTraceStateInfo, kTraceUtility, -1,
            "Loaded native condition variables");
        win_support_condition_variables_primitive = true;
      }
    }
  }
  if (!win_support_condition_variables_primitive) {
    return false;
  }
  PInitializeConditionVariable_(&condition_variable_);
  return true;
}

void ConditionVariableNativeWin::SleepCS(CriticalSectionWrapper& crit_sect) {
  SleepCS(crit_sect, INFINITE);
}

bool ConditionVariableNativeWin::SleepCS(CriticalSectionWrapper& crit_sect,
                                         unsigned long max_time_in_ms) {
  CriticalSectionWindows* cs =
      static_cast<CriticalSectionWindows*>(&crit_sect);
  BOOL ret_val = PSleepConditionVariableCS_(&condition_variable_,
                                            &(cs->crit), max_time_in_ms);
  return ret_val != 0;
}

void ConditionVariableNativeWin::Wake() {
  PWakeConditionVariable_(&condition_variable_);
}

void ConditionVariableNativeWin::WakeAll() {
  PWakeAllConditionVariable_(&condition_variable_);
}

}  // namespace webrtc