Implement circular queues for the C++ version of CPU profiler.

src/circular-queue-inl.h

+// Copyright 2010 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:
+//
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+//       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
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+//       with the distribution.
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+//       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
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+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_CIRCULAR_BUFFER_INL_H_
+#define V8_CIRCULAR_BUFFER_INL_H_
+
+#include "circular-queue.h"
+
+namespace v8 {
+namespace internal {
+
+
+template<typename Record>
+CircularQueue<Record>::CircularQueue(int desired_buffer_size_in_bytes)
+    : buffer_(NewArray<Record>(desired_buffer_size_in_bytes / sizeof(Record))),
+      buffer_end_(buffer_ + desired_buffer_size_in_bytes / sizeof(Record)),
+      enqueue_semaphore_(OS::CreateSemaphore((buffer_end_ - buffer_) - 1)),
+      enqueue_pos_(buffer_),
+      dequeue_pos_(buffer_) {
+  // To be able to distinguish between a full and an empty queue
+  // state, the queue must be capable of containing at least 2
+  // records.
+  ASSERT((buffer_end_ - buffer_) >= 2);
+}
+
+
+template<typename Record>
+CircularQueue<Record>::~CircularQueue() {
+  DeleteArray(buffer_);
+  delete enqueue_semaphore_;
+}
+
+
+template<typename Record>
+void CircularQueue<Record>::Dequeue(Record* rec) {
+  ASSERT(!IsEmpty());
+  *rec = *dequeue_pos_;
+  dequeue_pos_ = Next(dequeue_pos_);
+  // Tell we have a spare record.
+  enqueue_semaphore_->Signal();
+}
+
+
+template<typename Record>
+void CircularQueue<Record>::Enqueue(const Record& rec) {
+  // Wait until we have at least one spare record.
+  enqueue_semaphore_->Wait();
+  ASSERT(Next(enqueue_pos_) != dequeue_pos_);
+  *enqueue_pos_ = rec;
+  enqueue_pos_ = Next(enqueue_pos_);
+}
+
+
+template<typename Record>
+Record* CircularQueue<Record>::Next(Record* curr) {
+  return ++curr != buffer_end_ ? curr : buffer_;
+}
+
+
+void* SamplingCircularQueue::Enqueue() {
+  Cell* enqueue_pos = reinterpret_cast<Cell*>(
+      Thread::GetThreadLocal(producer_key_));
+  WrapPositionIfNeeded(&enqueue_pos);
+  Thread::SetThreadLocal(producer_key_, enqueue_pos + record_size_);
+  return enqueue_pos;
+}
+
+
+void SamplingCircularQueue::WrapPositionIfNeeded(
+    SamplingCircularQueue::Cell** pos) {
+  if (**pos == kEnd) *pos = buffer_;
+}
+
+
+} }  // namespace v8::internal
+
+#endif  // V8_CIRCULAR_BUFFER_INL_H_