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..01d8aba5aa19836b55c3a2cab90b5cdf7528928e |
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+++ b/webrtc/rtc_base/moving_max_counter.h |
@@ -0,0 +1,126 @@ |
+/* |
+ * Copyright (c) 2017 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_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|. |current_time_ms| in successive calls to Add and MovingMax |
+// should never decrease as if it's a wallclock time. |
+// Not thread-safe even if you only call const methods. |
+template <class T> |
+class MovingMaxCounter { |
+ public: |
+ explicit MovingMaxCounter(int64_t window_length_ms); |
+ // Advances the current time, and adds a new sample. The new current time must |
+ // be at least as large as the old current time. |
+ void Add(const T& sample, int64_t current_time_ms); |
+ // Advances the current time, and returns the maximum sample in the time |
+ // window ending at the current time. The new current time must be at least as |
+ // large as the old current time. |
+ rtc::Optional<T> Max(int64_t current_time_ms) const; |
+ void Reset(); |
+ |
+ private: |
+ // Throws out obsolete samples. Is |const| because it is always safe to throw |
+ // out old elements as long as |current_time_ms| parameters to public methods |
+ // are always increasing. |
+ void RollWindow(int64_t new_time_ms) const; |
+ const int64_t window_length_ms_; |
+ // 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_; |
+#if RTC_DCHECK_IS_ON |
+ mutable int64_t last_call_time_ms_; |
+#endif |
+ RTC_DISALLOW_COPY_AND_ASSIGN(MovingMaxCounter); |
+}; |
+ |
+template <class T> |
+MovingMaxCounter<T>::MovingMaxCounter(int64_t window_length_ms) |
+ : window_length_ms_(window_length_ms) |
+#if RTC_DCHECK_IS_ON |
+ , last_call_time_ms_(std::numeric_limits<int64_t>::min()) |
+#endif |
kwiberg-webrtc
2017/08/22 13:28:41
I think the compiler will complain about a misplac
ilnik
2017/08/22 14:11:34
It doesn't complain locally. Waiting for the trybo
ilnik
2017/08/22 16:12:44
Bots do not complain too.
kwiberg-webrtc
2017/08/22 21:40:46
Agh, it's just me who can't read. The parentheses
ilnik
2017/08/23 07:46:50
Yes, it might be more readable that way. Changing
|
+ {} |
+ |
+template <class T> |
+void MovingMaxCounter<T>::Add(const T& sample, int64_t current_time_ms) { |
+#if RTC_DCHECK_IS_ON |
+ RTC_DCHECK_GE(current_time_ms, last_call_time_ms_); |
+ last_call_time_ms_ = current_time_ms; |
+#endif |
+ RollWindow(current_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(); |
+ } |
+ // Add the new sample but only if there's no existing sample at the same time. |
+ // Due to checks above, already existing element will be larger and new sample |
+ // will never be a maximum in any window. |
+ if (samples_.empty() || samples_.back().first < current_time_ms) { |
+ samples_.emplace_back(std::make_pair(current_time_ms, sample)); |
+ } |
+} |
+ |
+template <class T> |
+rtc::Optional<T> MovingMaxCounter<T>::Max(int64_t current_time_ms) const { |
+#if RTC_DCHECK_IS_ON |
+ RTC_DCHECK_GE(current_time_ms, last_call_time_ms_); |
+ last_call_time_ms_ = current_time_ms; |
+#endif |
+ RollWindow(current_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 new_time_ms) const { |
+ const int64_t window_begin_ms = new_time_ms - window_length_ms_; |
+ auto it = samples_.begin(); |
+ while (it != samples_.end() && it->first < window_begin_ms) { |
+ ++it; |
+ } |
+ samples_.erase(samples_.begin(), it); |
+} |
+ |
+} // namespace rtc |
+ |
+#endif // WEBRTC_RTC_BASE_MOVING_MAX_COUNTER_H_ |