Import ConditionVariable class.

src/platform/condition-variable.h

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_PLATFORM_CONDITION_VARIABLE_H_
+#define V8_PLATFORM_CONDITION_VARIABLE_H_
+
+#include "platform/mutex.h"
+
+namespace v8 {
+namespace internal {
+
+// Forward declarations.
+class ConditionVariableEvent;
+class TimeDelta;
+
+// -----------------------------------------------------------------------------
+// ConditionVariable
+//
+// This class is a synchronization primitive that can be used to block a thread,
+// or multiple threads at the same time, until:
+// - a notification is received from another thread,
+// - a timeout expires, or
+// - a spurious wakeup occurs
+// Any thread that intends to wait on a ConditionVariable has to acquire a lock
+// on a Mutex first. The |Wait()| and |WaitFor()| operations atomically release
+// the mutex and suspend the execution of the calling thread. When the condition
+// variable is notified, the thread is awakened, and the mutex is reacquired.
+
+class ConditionVariable V8_FINAL {
+ public:
+  ConditionVariable();
+  ~ConditionVariable();
+
+  // If any threads are waiting on this condition variable, calling
+  // |NotifyOne()| unblocks one of the waiting threads.
+  void NotifyOne();
+
+  // Unblocks all threads currently waiting for this condition variable.
+  void NotifyAll();
+
+  // |Wait()| causes the calling thread to block until the condition variable is
+  // notified or a spurious wakeup occurs. Atomically releases the mutex, blocks
+  // the current executing thread, and adds it to the list of threads waiting on
+  // this condition variable. The thread will be unblocked when |NotifyAll()| or
+  // |NotifyOne()| is executed. It may also be unblocked spuriously. When
+  // unblocked, regardless of the reason, the lock on the mutex is reacquired
+  // and |Wait()| exits.
+  void Wait(Mutex* mutex);
+
+  // Atomically releases the mutex, blocks the current executing thread, and
+  // adds it to the list of threads waiting on this condition variable. The
+  // thread will be unblocked when |NotifyAll()| or |NotifyOne()| is executed,
+  // or when the relative timeout |rel_time| expires. It may also be unblocked
+  // spuriously. When unblocked, regardless of the reason, the lock on the mutex
+  // is reacquired and |WaitFor()| exits. Returns true if the condition variable
+  // was notified prior to the timeout.
+  bool WaitFor(Mutex* mutex, const TimeDelta& rel_time) V8_WARN_UNUSED_RESULT;
+
+  // The implementation-defined native handle type.
+#if V8_OS_POSIX
+  typedef pthread_cond_t NativeHandle;
+#elif V8_OS_WIN
+  struct Event;
+  class NativeHandle V8_FINAL {
+   public:
+    NativeHandle() : waitlist_(NULL), freelist_(NULL) {}
+    ~NativeHandle();
+
+    Event* Pre() V8_WARN_UNUSED_RESULT;
+    void Post(Event* event, bool result);
+
+    Mutex* mutex() { return &mutex_; }
+    Event* waitlist() { return waitlist_; }
+
+   private:
+    Event* waitlist_;
+    Event* freelist_;
+    Mutex mutex_;
+
+    DISALLOW_COPY_AND_ASSIGN(NativeHandle);
+  };
+#endif
+
+  NativeHandle& native_handle() V8_WARN_UNUSED_RESULT {
+    return native_handle_;
+  }
+  const NativeHandle& native_handle() const V8_WARN_UNUSED_RESULT {
+    return native_handle_;
+  }
+
+ private:
+  NativeHandle native_handle_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConditionVariable);
+};
+
+
+// POD ConditionVariable initialized lazily (i.e. the first time Pointer() is
+// called).
+// Usage:
+//   static LazyConditionVariable my_condvar =
+//       LAZY_CONDITION_VARIABLE_INITIALIZER;
+//
+//   void my_function() {
+//     LockGuard<Mutex> lock_guard(&my_mutex);
+//     my_condvar.Pointer()->Wait(&my_mutex);
+//   }
+typedef LazyStaticInstance<ConditionVariable,
+                           DefaultConstructTrait<ConditionVariable>,
+                           ThreadSafeInitOnceTrait>::type LazyConditionVariable;
+
+#define LAZY_CONDITION_VARIABLE_INITIALIZER LAZY_STATIC_INSTANCE_INITIALIZER
+
+} }  // namespace v8::internal
+
+#endif  // V8_PLATFORM_CONDITION_VARIABLE_H_