Index: webrtc/rtc_base/moving_max_counter.h |
diff --git a/webrtc/rtc_base/moving_max_counter.h b/webrtc/rtc_base/moving_max_counter.h |
new file mode 100644 |
index 0000000000000000000000000000000000000000..71c6e588b7f4a70faea54eddfcaab65b3c80bd12 |
--- /dev/null |
+++ b/webrtc/rtc_base/moving_max_counter.h |
@@ -0,0 +1,108 @@ |
+/* |
+ * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. |
ilnik
2017/08/18 13:31:17
changed to 2017. Will upload in the next patch set
|
+ * |
+ * 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_RTC_BASE_MOVING_MAX_COUNTER_H_ |
+#define WEBRTC_RTC_BASE_MOVING_MAX_COUNTER_H_ |
+ |
+#include <stdint.h> |
+ |
+#include <deque> |
+#include <limits> |
+#include <utility> |
+ |
+#include "webrtc/rtc_base/checks.h" |
+#include "webrtc/rtc_base/constructormagic.h" |
+#include "webrtc/rtc_base/optional.h" |
+ |
+namespace rtc { |
+ |
+// Implements moving max: can add samples to it and calculate maximum over some |
+// fixed moving window. |
+// |
+// Window size is configured at constructor. |
+// Samples can be added with |Add()| and max over current window is returned by |
+// |MovingMax|. |time_ms| in consecutive calls to Add and MovingMax should never |
+// decrease as if it's a current time. |
+// Not thread-safe. |
+template <class T> |
+class MovingMaxCounter { |
+ public: |
+ explicit MovingMaxCounter(int window_length_ms); |
sprang_webrtc
2017/08/21 14:41:09
For consistency, maybe use int64_t for times
ilnik
2017/08/21 14:59:27
Done.
|
+ // Adds new sample at a given current time. |
+ void Add(const T& sample, int64_t time_ms); |
+ // Returns max sample in window ending at a given current time. |
+ rtc::Optional<T> MovingMax(int64_t time_ms) const; |
sprang_webrtc
2017/08/21 14:41:09
Remove Moving from name
ilnik
2017/08/21 14:59:27
Done.
|
+ void Reset(); |
+ |
+ private: |
+ // Throws out obsolete samples. Is |const| because it is always safe to throw |
+ // out old elements as long as |time_ms| parameters to public methods are |
+ // always increasing. |
+ void RollWindow(int64_t time_ms) const; |
+ int window_length_ms_; |
sprang_webrtc
2017/08/21 14:41:09
const
ilnik
2017/08/21 14:59:27
Done.
|
+ // Samples in the window are stored as pairs <time, sample> in this deque in |
+ // chronological order. Samples what can't be maximum in any window are |
+ // thrown out - deque always contains non-increasing sequence of samples. |
+ // Is |mutable| because |MovingMax()| may be called on const instances yet it |
+ // will remove obsolete samples to speed up consecutive calls. |
+ mutable std::deque<std::pair<int64_t, T>> samples_; |
+ mutable int64_t last_call_time_ms_; |
+ |
+ RTC_DISALLOW_COPY_AND_ASSIGN(MovingMaxCounter); |
+}; |
+ |
+template <class T> |
+MovingMaxCounter<T>::MovingMaxCounter(int window_length_ms) |
+ : window_length_ms_(window_length_ms), |
+ last_call_time_ms_(std::numeric_limits<int64_t>::min()) {} |
+ |
+template <class T> |
+void MovingMaxCounter<T>::Add(const T& sample, int64_t time_ms) { |
+ RTC_DCHECK_GE(time_ms, last_call_time_ms_); |
+ last_call_time_ms_ = time_ms; |
+ RollWindow(time_ms); |
+ // Remove samples what will never be maximum in any window: newly added sample |
+ // will always be in all windows the previous samples are. Thus, smaller |
+ // samples could be removed. This will maintain the invariant - deque contains |
+ // non-increasing sequence of values. |
+ while (!samples_.empty() && samples_.back().second < sample) { |
+ samples_.pop_back(); |
+ } |
+ samples_.emplace_back(std::make_pair(time_ms, sample)); |
sprang_webrtc
2017/08/21 14:41:09
if samples_[time_ms] exists, you can just update t
ilnik
2017/08/21 14:59:27
Seems like an unneeded optimization to me. If the
sprang_webrtc
2017/08/22 08:44:50
Agree that it should not matter for the use case i
ilnik
2017/08/22 09:06:39
Fair enough. I am adding the checks now.
|
+} |
+ |
+template <class T> |
+rtc::Optional<T> MovingMaxCounter<T>::MovingMax(int64_t time_ms) const { |
+ RTC_DCHECK_GE(time_ms, last_call_time_ms_); |
+ last_call_time_ms_ = time_ms; |
+ RollWindow(time_ms); |
+ rtc::Optional<T> res; |
+ if (!samples_.empty()) { |
+ res.emplace(samples_.front().second); |
+ } |
+ return res; |
+} |
+ |
+template <class T> |
+void MovingMaxCounter<T>::Reset() { |
+ samples_.clear(); |
+} |
+ |
+template <class T> |
+void MovingMaxCounter<T>::RollWindow(int64_t time_ms) const { |
+ int64_t window_begin_ms = time_ms - window_length_ms_; |
+ while (!samples_.empty() && samples_.front().first < window_begin_ms) { |
+ samples_.pop_front(); |
+ } |
+} |
+ |
+} // namespace rtc |
+ |
+#endif // WEBRTC_RTC_BASE_MOVING_MAX_COUNTER_H_ |