| // 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/lazy-instance.h" |
| #if V8_OS_WIN |
| #include "src/base/win32-headers.h" |
| #endif |
| |
| #if V8_OS_MACOSX |
| #include <mach/semaphore.h> // NOLINT |
| #elif V8_OS_POSIX |
| #include <semaphore.h> // NOLINT |
| #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 Semaphore FINAL { |
| public: |
| explicit Semaphore(int count); |
| ~Semaphore(); |
| |
| // Increments the semaphore counter. |
| void Signal(); |
| |
| // Suspends the calling thread until the semaphore counter is non zero |
| // and then decrements the semaphore counter. |
| void Wait(); |
| |
| // Suspends the calling thread until the counter is non zero or the timeout |
| // time has passed. If timeout happens the return value is false and the |
| // counter is unchanged. Otherwise the semaphore counter is decremented and |
| // true is returned. |
| bool WaitFor(const TimeDelta& rel_time) WARN_UNUSED_RESULT; |
| |
| #if V8_OS_MACOSX |
| typedef semaphore_t NativeHandle; |
| #elif V8_OS_POSIX |
| typedef sem_t NativeHandle; |
| #elif V8_OS_WIN |
| typedef HANDLE NativeHandle; |
| #endif |
| |
| NativeHandle& native_handle() { |
| return native_handle_; |
| } |
| const NativeHandle& native_handle() const { |
| return native_handle_; |
| } |
| |
| private: |
| NativeHandle native_handle_; |
| |
| DISALLOW_COPY_AND_ASSIGN(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 { |
| static Semaphore* Create() { |
| return new Semaphore(N); |
| } |
| }; |
| |
| template <int N> |
| struct LazySemaphore { |
| typedef typename LazyDynamicInstance<Semaphore, CreateSemaphoreTrait<N>, |
| ThreadSafeInitOnceTrait>::type type; |
| }; |
| |
| #define LAZY_SEMAPHORE_INITIALIZER LAZY_DYNAMIC_INSTANCE_INITIALIZER |
| |
| } } // namespace v8::base |
| |
| #endif // V8_BASE_PLATFORM_SEMAPHORE_H_ |