Index: webrtc/common_audio/swap_queue.h |
diff --git a/webrtc/common_audio/swap_queue.h b/webrtc/common_audio/swap_queue.h |
new file mode 100644 |
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+++ b/webrtc/common_audio/swap_queue.h |
@@ -0,0 +1,213 @@ |
+/* |
+ * Copyright (c) 2015 The WebRTC 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 in the root of the source |
+ * tree. An additional intellectual property rights grant can be found |
+ * in the file PATENTS. All contributing project authors may |
+ * be found in the AUTHORS file in the root of the source tree. |
+ */ |
+ |
+#ifndef WEBRTC_COMMON_AUDIO_SWAP_QUEUE_H_ |
+#define WEBRTC_COMMON_AUDIO_SWAP_QUEUE_H_ |
+ |
+#include <algorithm> |
+#include <utility> |
+#include <vector> |
+ |
+#include "webrtc/base/checks.h" |
+#include "webrtc/base/criticalsection.h" |
+ |
+namespace webrtc { |
+ |
+namespace internal { |
+ |
+// This class is a fixed-size queue. A producer calls Insert() to insert |
+// an element of type T at the back of the queue, and a consumer calls |
+// Remove() to remove an element from the front of the queue. It's safe |
+// for the producer(s) and the consumer(s) to access the queue |
+// concurrently, from different threads. |
+// |
+// To avoid the construction, copying, and destruction of Ts that a naive |
+// queue implementation would require, for each "full" T passed from |
+// producer to consumer, SwapQueue<T> passes an "empty" T in the other |
+// direction (an "empty" T is one that contains nothing of value for the |
+// consumer). This bidirectional movement is implemented with swap(). |
+// |
+// // Create queue: |
+// Bottle proto(568); // Prepare an empty Bottle. Heap allocates space for |
+// // 568 ml. |
+// SwapQueue<Bottle> q(N, proto); // Init queue with N copies of proto. |
+// // Also heap. |
kwiberg-webrtc
2015/10/27 12:05:13
Since it doesn't fit on one line anyway:
"Also he
peah-webrtc
2015/10/29 06:15:14
Done.
|
+// // Producer pseudo-code: |
+// Bottle b(568); // Prepare an empty Bottle. Heap allocates space for 568 ml. |
+// loop { |
+// b.Fill(amount); // Where amount <= 568 ml. |
+// q.Insert(&b); // Swap our full Bottle for an empty one from q. |
+// } |
+ |
+// // Consumer pseudo-code: |
+// Bottle b(568); // Prepare an empty Bottle. Heap allocates space for 568 ml. |
+// loop { |
+// q.Remove(&b); // Swap our empty Bottle for the next-in-line full Bottle. |
+// Drink(&b); |
+// } |
+ |
+// For a well-behaved Bottle class, there are no allocations in the |
+// producer, since it just fills an empty Bottle that's already large |
+// enough; no deallocations in the consumer, since it returns each empty |
+// Bottle to the queue after having drunk it; and no copies along the |
+// way, since the queue uses swap() everywhere to move full Bottles in |
+// one direction and empty ones in the other. |
kwiberg-webrtc
2015/10/27 12:05:13
Move lines 25-61 to just before the SwapQueue clas
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ |
+// (Internal; please don't use outside this file.) |
+// Default item invariance verifier callback function. |
+template <typename T> |
+bool SwapQueueItemVerifierFunction(const T&) { |
kwiberg-webrtc
2015/10/27 12:05:13
Prepend "Default" or "Noop" or something to this n
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ return true; |
+} |
+ |
+} // namespace internal |
+ |
+// Functor to use when supplying a verifier function for the queue item |
+// verifcation. |
+template <typename T, |
+ bool (*QueueItemVerifierFunction)(const T&) = |
+ internal::SwapQueueItemVerifierFunction> |
+class SwapQueueItemVerifier { |
+ public: |
+ bool operator()(const T& t) const { return QueueItemVerifierFunction(t); } |
+}; |
+ |
+// Queue of type T with an optional invariance verifier callback functor that |
+// verifies that the queue elements are compliant to a certain requirement. |
+template <typename T, typename QueueItemVerifier = SwapQueueItemVerifier<T> > |
kwiberg-webrtc
2015/10/27 12:05:13
"> >" -> ">>"
peah-webrtc
2015/10/29 06:15:14
Done.
|
+class SwapQueue { |
+ public: |
+ // Creates a queue of size size and fills it with the specified number of |
+ // default constructed Ts. |
+ explicit SwapQueue(size_t size) : queue_(size) { |
+ RTC_DCHECK(VerifyQueueContent()); |
+ } |
+ |
+ // Creates a queue of size size and fills it with the specified number of |
+ // default constructed Ts and accepts a functor to use for initializing the |
+ // item verification functor. |
+ SwapQueue(size_t size, const QueueItemVerifier& queue_item_verifier) |
+ : queue_item_verifier_(queue_item_verifier), queue_(size) { |
+ RTC_DCHECK(VerifyQueueContent()); |
+ } |
+ |
+ // Creates a queue of size size and fills it with copies of prototype. |
+ SwapQueue(size_t size, const T& prototype) : queue_(size, prototype) { |
+ RTC_DCHECK(VerifyQueueContent()); |
+ } |
+ |
+ // Creates a queue of size size and fills it with copies of prototype and |
+ // accepts a functor to use for initializing the item verification functor. |
+ SwapQueue(size_t size, |
+ QueueItemVerifier const& queue_item_verifier, |
+ const T& prototype) |
+ : queue_(size, prototype), queue_item_verifier_(queue_item_verifier) { |
+ RTC_DCHECK(VerifyQueueContent()); |
+ } |
+ |
+ // Resets the queue to have zero content. |
kwiberg-webrtc
2015/10/27 12:05:13
Point out that the number of slots in the queue do
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ void Clear() { |
+ rtc::CritScope cs(&crit_queue_); |
+ next_write_index_ = 0; |
+ next_read_index_ = 0; |
+ num_elements_ = 0; |
+ } |
+ |
+ // Inserts a T into the queue by swapping *input with an element already in |
+ // the queue (an object from the unordered bunch). |
kwiberg-webrtc
2015/10/27 12:05:13
The doc now talks about "empty" and "full" Ts agai
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ // Returns true if the item was inserted or false if not (the queue was full). |
+ // When specified, the T given in *input must pass the ItemVerifier() test. |
+ // The contents of *input after the call are then also guaranteed to pass the |
+ // ItemVerifier() test. |
+ bool Insert(T* input) { |
kwiberg-webrtc
2015/10/27 12:05:13
Annotate this with WARN_UNUSED_RESULT?
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ RTC_DCHECK(input); |
+ RTC_DCHECK(queue_item_verifier_(*input)); |
+ |
+ rtc::CritScope cs(&crit_queue_); |
+ |
+ if (num_elements_ == queue_.size()) { |
+ return false; |
+ } |
+ |
+ using std::swap; |
+ swap(*input, queue_[next_write_index_]); |
+ |
+ next_write_index_++; |
kwiberg-webrtc
2015/10/27 12:05:13
In general, prefer the prefix forms. (They're some
peah-webrtc
2015/10/29 06:15:14
Thanks! Will do!
Done.
|
+ if (next_write_index_ == queue_.size()) { |
+ next_write_index_ = 0; |
+ } |
+ |
+ num_elements_++; |
+ return true; |
+ } |
+ |
+ // Removes a T from the queue by swapping *output with an element in the |
+ // queue. |
+ // The T in *output before the call is swapped into the queue (into the |
+ // unordered bunch in the queue). |
kwiberg-webrtc
2015/10/27 12:05:13
See comment above. Maybe
Removes the frontmost
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ // Returns true if an item could be removed or false if not (the queue was |
+ // empty). When specified, The T given in *output must pass the ItemVerifier() |
+ // test and the contents of *output after the call are then also guaranteed to |
+ // pass the ItemVerifier() test. |
+ bool Remove(T* output) { |
kwiberg-webrtc
2015/10/27 12:05:13
WARN_UNUSED_RESULT?
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ RTC_DCHECK(output); |
+ RTC_DCHECK(queue_item_verifier_(*output)); |
+ |
+ rtc::CritScope cs(&crit_queue_); |
+ |
+ if (num_elements_ == 0) { |
+ return false; |
+ } |
+ |
+ using std::swap; |
+ swap(*output, queue_[next_read_index_]); |
+ |
+ next_read_index_++; |
+ if (next_read_index_ == queue_.size()) { |
+ next_read_index_ = 0; |
+ } |
+ |
+ num_elements_--; |
+ return true; |
+ } |
+ |
+ private: |
+ // Verify that the queue content complies with the ItemVerifier test. |
+ bool VerifyQueueContent() { |
kwiberg-webrtc
2015/10/27 12:05:13
I'd say it ought to be "Contents". See e.g. http:/
peah-webrtc
2015/10/29 06:15:14
Done.
|
+ rtc::CritScope cs(&crit_queue_); |
+ for (const auto& v : queue_) { |
+ RTC_DCHECK(queue_item_verifier_(v)); |
+ } |
+ return true; |
+ } |
+ |
+ QueueItemVerifier queue_item_verifier_; |
+ |
+ rtc::CriticalSection crit_queue_; |
+ |
+ // (next_read_index_ + num_elements_) % queue_.size() = |
+ // next_write_index_ |
+ // 0 <= next_write_index_ < queue.size() |
+ size_t next_write_index_ GUARDED_BY(crit_queue_) = 0; |
+ // 0 <= next_read_index_ < queue.size() |
+ size_t next_read_index_ GUARDED_BY(crit_queue_) = 0; |
+ |
+ // 0 <= num_elements_ < queue.size() |
+ size_t num_elements_ GUARDED_BY(crit_queue_) = 0; |
+ |
+ // queue_.size() is constant. |
+ std::vector<T> queue_ GUARDED_BY(crit_queue_); |
+ |
+ RTC_DISALLOW_COPY_AND_ASSIGN(SwapQueue); |
+}; |
+ |
+} // namespace webrtc |
+ |
+#endif // WEBRTC_COMMON_AUDIO_SWAP_QUEUE_H_ |