chromium/v8/src/base/platform/semaphore.h

// Copyright 2013 the V8 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.

#ifndef V8_BASE_PLATFORM_SEMAPHORE_H_
#define V8_BASE_PLATFORM_SEMAPHORE_H_

#include "src/base/base-export.h"
#include "src/base/lazy-instance.h"
#if V8_OS_WIN
#include "src/base/win32-headers.h"
#endif

#if V8_OS_DARWIN
#include <dispatch/dispatch.h>
#elif V8_OS_ZOS
#include "zos-semaphore.h"
#elif V8_OS_POSIX
#include <semaphore.h>
#endif

#if V8_OS_STARBOARD
#include "starboard/common/semaphore.h"
#endif

namespace v8 {
namespace base {

// Forward declarations.
class TimeDelta;

// ----------------------------------------------------------------------------
// Semaphore
//
// A semaphore object is a synchronization object that maintains a count. The
// count is decremented each time a thread completes a wait for the semaphore
// object and incremented each time a thread signals the semaphore. When the
// count reaches zero,  threads waiting for the semaphore blocks until the
// count becomes non-zero.

class V8_BASE_EXPORT Semaphore { … };

// POD Semaphore initialized lazily (i.e. the first time Pointer() is called).
// Usage:
//   // The following semaphore starts at 0.
//   static LazySemaphore<0>::type my_semaphore = LAZY_SEMAPHORE_INITIALIZER;
//
//   void my_function() {
//     // Do something with my_semaphore.Pointer().
//   }
//

template <int N>
struct CreateSemaphoreTrait { … };

template <int N>
struct LazySemaphore { … };

#define LAZY_SEMAPHORE_INITIALIZER …

}  // namespace base
}  // namespace v8

#endif  // V8_BASE_PLATFORM_SEMAPHORE_H_