Refactor NACK bitrate allocation

webrtc/base/rate_limiter_unittest.cc

+/*
+ *  Copyright (c) 2016 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.
+ */
+
+#include <algorithm>
+#include <memory>
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/base/rate_limiter.h"
+#include "webrtc/system_wrappers/include/clock.h"
+
+namespace webrtc {
+
+class RateLimitTest : public ::testing::Test {
+ public:
+  RateLimitTest()
+      : clock_(0), rate_limiter(new RateLimiter(&clock_, kWindowSize)) {}
+  virtual ~RateLimitTest() {}
+
+  void SetUp() override { rate_limiter->SetMaxRate(kMaxRateBps); }
+
+ protected:
+  static const int64_t kWindowSize = 1000;

[danilchap, 2016/07/04 12:22:57]

constexpr kWindowSizeMs

[sprang_webrtc, 2016/07/04 12:47:00]

Done.

+  static const uint32_t kMaxRateBps = 100000;

[danilchap, 2016/07/04 12:22:57]

constexpr

[sprang_webrtc, 2016/07/04 12:47:00]

Done.

+  SimulatedClock clock_;
+  std::unique_ptr<RateLimiter> rate_limiter;
+};
+
+TEST_F(RateLimitTest, IncreasingMaxRate) {
+  // Fill rate, extend window to full size.
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 16));

[danilchap, 2016/07/04 12:22:57]

Can you expand this line to avoid thinking that TryRate tries to use kmaxRATEbps
devided by magical constant 16:

TryRate(bitrate/16) actually means
size_t kSizeFillingBandwidthBytes = (kMaxRateBps / kBitsInByte) * (kWindowSize /
kMsInS);  // last multiplier = 1, but explains how bytes/s got converted into
bytes
rate_limiter->TryUseRate(kSizeFillingBandwidthBytes / 2);

[sprang_webrtc, 2016/07/04 12:47:00]

Done.

+  clock_.AdvanceTimeMilliseconds(kWindowSize - 1);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 16));
+
+  // All rate consumed.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+
+  // Double the available rate and fill that too.
+  rate_limiter->SetMaxRate(kMaxRateBps * 2);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 8));
+
+  // All rate consumed again.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+}
+
+TEST_F(RateLimitTest, DecreasingMaxRate) {
+  // Fill rate, extend window to full size.
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 16));

[danilchap, 2016/07/04 12:22:57]

same here (which hints constant with packet size that fills kMaxRateBps alone
may be in RateLimitTest.

[sprang_webrtc, 2016/07/04 12:47:00]

Done.

+  clock_.AdvanceTimeMilliseconds(kWindowSize - 1);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 16));
+
+  // All rate consumed.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+
+  // Halve the available rate and move window so half of the data falls out.
+  rate_limiter->SetMaxRate(kMaxRateBps / 2);
+  clock_.AdvanceTimeMilliseconds(1);
+
+  // All rate still consumed.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+}
+
+TEST_F(RateLimitTest, ChangingWindowSize) {
+  // Fill rate, extend window to full size.
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 16));
+  clock_.AdvanceTimeMilliseconds(kWindowSize - 1);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 16));
+
+  // All rate consumed.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+
+  // Decrease window size so half of the data falls out.
+  rate_limiter->SetWindowSize(kWindowSize / 2);
+  // Average rate should still be the same, so rate is still all consumed.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+
+  // Increase window size again. Now the rate is only half used (removed data
+  // points don't come back to life).
+  rate_limiter->SetWindowSize(kWindowSize);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kMaxRateBps / 16));
+
+  // All rate consumed again.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+}
+
+TEST_F(RateLimitTest, SingleUsageAlwaysOk) {
+  // Using more bytes than can fit in a window is OK for a single packet.
+  EXPECT_TRUE(rate_limiter->TryUseRate((kMaxRateBps / 8) + 1));
+}
+
+}  // namespace webrtc