text: // 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.
  
  #include "src/base/platform/semaphore.h"
  
  #if V8_OS_MACOSX
  #include <dispatch/dispatch.h>
  #endif
  
  #include <errno.h>
  
  #include "src/base/logging.h"
  #include "src/base/platform/elapsed-timer.h"
  #include "src/base/platform/time.h"
  
  namespace v8 {
  namespace base {
  
  #if V8_OS_MACOSX
  
  Semaphore::Semaphore(int count) {
    native_handle_ = dispatch_semaphore_create(count);
    DCHECK(native_handle_);
  }
  
  Semaphore::~Semaphore() { dispatch_release(native_handle_); }
  
  void Semaphore::Signal() { dispatch_semaphore_signal(native_handle_); }
  
  void Semaphore::Wait() {
    dispatch_semaphore_wait(native_handle_, DISPATCH_TIME_FOREVER);
  }
  
  
  bool Semaphore::WaitFor(const TimeDelta& rel_time) {
    dispatch_time_t timeout =
        dispatch_time(DISPATCH_TIME_NOW, rel_time.InNanoseconds());
    return dispatch_semaphore_wait(native_handle_, timeout) == 0;
  }
  
  #elif V8_OS_POSIX
  
  Semaphore::Semaphore(int count) {
    DCHECK_GE(count, 0);
    int result = sem_init(&native_handle_, 0, count);
    DCHECK_EQ(0, result);
    USE(result);
  }
  
  
  Semaphore::~Semaphore() {
    int result = sem_destroy(&native_handle_);
    DCHECK_EQ(0, result);
    USE(result);
  }
  
  void Semaphore::Signal() {
    int result = sem_post(&native_handle_);
    // This check may fail with <libc-2.21, which we use on the try bots, if the
    // semaphore is destroyed while sem_post is still executed. A work around is
    // to extend the lifetime of the semaphore.
    if (result != 0) {
      FATAL("Error when signaling semaphore, errno: %d", errno);
    }
  }
  
  
  void Semaphore::Wait() {
    while (true) {
      int result = sem_wait(&native_handle_);
      if (result == 0) return;  // Semaphore was signalled.
      // Signal caused spurious wakeup.
      DCHECK_EQ(-1, result);
      DCHECK_EQ(EINTR, errno);
    }
  }
  
  
  bool Semaphore::WaitFor(const TimeDelta& rel_time) {
    // Compute the time for end of timeout.
    const Time time = Time::NowFromSystemTime() + rel_time;
    const struct timespec ts = time.ToTimespec();
  
    // Wait for semaphore signalled or timeout.
    while (true) {
      int result = sem_timedwait(&native_handle_, &ts);
      if (result == 0) return true;  // Semaphore was signalled.
  #if V8_LIBC_GLIBC && !V8_GLIBC_PREREQ(2, 4)
      if (result > 0) {
        // sem_timedwait in glibc prior to 2.3.4 returns the errno instead of -1.
        errno = result;
        result = -1;
      }
  #endif
      if (result == -1 && errno == ETIMEDOUT) {
        // Timed out while waiting for semaphore.
        return false;
      }
      // Signal caused spurious wakeup.
      DCHECK_EQ(-1, result);
      DCHECK_EQ(EINTR, errno);
    }
  }
  
  #elif V8_OS_WIN
  
  Semaphore::Semaphore(int count) {
    DCHECK_GE(count, 0);
    native_handle_ = ::CreateSemaphoreA(nullptr, count, 0x7FFFFFFF, nullptr);
    DCHECK_NOT_NULL(native_handle_);
  }
  
  
  Semaphore::~Semaphore() {
    BOOL result = CloseHandle(native_handle_);
    DCHECK(result);
    USE(result);
  }
  
  void Semaphore::Signal() {
    LONG dummy;
    BOOL result = ReleaseSemaphore(native_handle_, 1, &dummy);
    DCHECK(result);
    USE(result);
  }
  
  
  void Semaphore::Wait() {
    DWORD result = WaitForSingleObject(native_handle_, INFINITE);
    DCHECK(result == WAIT_OBJECT_0);
    USE(result);
  }
  
  
  bool Semaphore::WaitFor(const TimeDelta& rel_time) {
    TimeTicks now = TimeTicks::Now();
    TimeTicks end = now + rel_time;
    while (true) {
      int64_t msec = (end - now).InMilliseconds();
      if (msec >= static_cast<int64_t>(INFINITE)) {
        DWORD result = WaitForSingleObject(native_handle_, INFINITE - 1);
        if (result == WAIT_OBJECT_0) {
          return true;
        }
        DCHECK(result == WAIT_TIMEOUT);
        now = TimeTicks::Now();
      } else {
        DWORD result = WaitForSingleObject(
            native_handle_, (msec < 0) ? 0 : static_cast<DWORD>(msec));
        if (result == WAIT_TIMEOUT) {
          return false;
        }
        DCHECK(result == WAIT_OBJECT_0);
        return true;
      }
    }
  }
  
  #endif  // V8_OS_MACOSX
  
  }  // namespace base
  }  // namespace v8
  