Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame^] | 1 | // Copyright 2013 the V8 project 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 | #ifndef V8_BASE_PLATFORM_SEMAPHORE_H_ |
| 6 | #define V8_BASE_PLATFORM_SEMAPHORE_H_ |
| 7 | |
| 8 | #include "src/base/lazy-instance.h" |
| 9 | #if V8_OS_WIN |
| 10 | #include "src/base/win32-headers.h" |
| 11 | #endif |
| 12 | |
| 13 | #if V8_OS_MACOSX |
| 14 | #include <mach/semaphore.h> // NOLINT |
| 15 | #elif V8_OS_POSIX |
| 16 | #include <semaphore.h> // NOLINT |
| 17 | #endif |
| 18 | |
| 19 | namespace v8 { |
| 20 | namespace base { |
| 21 | |
| 22 | // Forward declarations. |
| 23 | class TimeDelta; |
| 24 | |
| 25 | // ---------------------------------------------------------------------------- |
| 26 | // Semaphore |
| 27 | // |
| 28 | // A semaphore object is a synchronization object that maintains a count. The |
| 29 | // count is decremented each time a thread completes a wait for the semaphore |
| 30 | // object and incremented each time a thread signals the semaphore. When the |
| 31 | // count reaches zero, threads waiting for the semaphore blocks until the |
| 32 | // count becomes non-zero. |
| 33 | |
| 34 | class Semaphore FINAL { |
| 35 | public: |
| 36 | explicit Semaphore(int count); |
| 37 | ~Semaphore(); |
| 38 | |
| 39 | // Increments the semaphore counter. |
| 40 | void Signal(); |
| 41 | |
| 42 | // Suspends the calling thread until the semaphore counter is non zero |
| 43 | // and then decrements the semaphore counter. |
| 44 | void Wait(); |
| 45 | |
| 46 | // Suspends the calling thread until the counter is non zero or the timeout |
| 47 | // time has passed. If timeout happens the return value is false and the |
| 48 | // counter is unchanged. Otherwise the semaphore counter is decremented and |
| 49 | // true is returned. |
| 50 | bool WaitFor(const TimeDelta& rel_time) WARN_UNUSED_RESULT; |
| 51 | |
| 52 | #if V8_OS_MACOSX |
| 53 | typedef semaphore_t NativeHandle; |
| 54 | #elif V8_OS_POSIX |
| 55 | typedef sem_t NativeHandle; |
| 56 | #elif V8_OS_WIN |
| 57 | typedef HANDLE NativeHandle; |
| 58 | #endif |
| 59 | |
| 60 | NativeHandle& native_handle() { |
| 61 | return native_handle_; |
| 62 | } |
| 63 | const NativeHandle& native_handle() const { |
| 64 | return native_handle_; |
| 65 | } |
| 66 | |
| 67 | private: |
| 68 | NativeHandle native_handle_; |
| 69 | |
| 70 | DISALLOW_COPY_AND_ASSIGN(Semaphore); |
| 71 | }; |
| 72 | |
| 73 | |
| 74 | // POD Semaphore initialized lazily (i.e. the first time Pointer() is called). |
| 75 | // Usage: |
| 76 | // // The following semaphore starts at 0. |
| 77 | // static LazySemaphore<0>::type my_semaphore = LAZY_SEMAPHORE_INITIALIZER; |
| 78 | // |
| 79 | // void my_function() { |
| 80 | // // Do something with my_semaphore.Pointer(). |
| 81 | // } |
| 82 | // |
| 83 | |
| 84 | template <int N> |
| 85 | struct CreateSemaphoreTrait { |
| 86 | static Semaphore* Create() { |
| 87 | return new Semaphore(N); |
| 88 | } |
| 89 | }; |
| 90 | |
| 91 | template <int N> |
| 92 | struct LazySemaphore { |
| 93 | typedef typename LazyDynamicInstance<Semaphore, CreateSemaphoreTrait<N>, |
| 94 | ThreadSafeInitOnceTrait>::type type; |
| 95 | }; |
| 96 | |
| 97 | #define LAZY_SEMAPHORE_INITIALIZER LAZY_DYNAMIC_INSTANCE_INITIALIZER |
| 98 | |
| 99 | } } // namespace v8::base |
| 100 | |
| 101 | #endif // V8_BASE_PLATFORM_SEMAPHORE_H_ |