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_, kWindowSizeMs)) {}
+  virtual ~RateLimitTest() {}
+
+  void SetUp() override { rate_limiter->SetMaxRate(kMaxRateBps); }
+
+ protected:
+  static constexpr int64_t kWindowSizeMs = 1000;
+  static constexpr uint32_t kMaxRateBps = 100000;
+  // Bytes needed to completely saturate the rate limiter.
+  static constexpr size_t kRateFillingBytes =
+      (kMaxRateBps * kWindowSizeMs) / (8 * 1000);
+  SimulatedClock clock_;
+  std::unique_ptr<RateLimiter> rate_limiter;
+};
+
+TEST_F(RateLimitTest, IncreasingMaxRate) {
+  // Fill rate, extend window to full size.
+  EXPECT_TRUE(rate_limiter->TryUseRate(kRateFillingBytes / 2));
+  clock_.AdvanceTimeMilliseconds(kWindowSizeMs - 1);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kRateFillingBytes / 2));
+
+  // 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(kRateFillingBytes));
+
+  // 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(kRateFillingBytes / 2));
+  clock_.AdvanceTimeMilliseconds(kWindowSizeMs - 1);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kRateFillingBytes / 2));
+
+  // 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(kRateFillingBytes / 2));
+  clock_.AdvanceTimeMilliseconds(kWindowSizeMs - 1);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kRateFillingBytes / 2));
+
+  // All rate consumed.
+  EXPECT_FALSE(rate_limiter->TryUseRate(1));
+
+  // Decrease window size so half of the data falls out.
+  rate_limiter->SetWindowSize(kWindowSizeMs / 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(kWindowSizeMs);
+  EXPECT_TRUE(rate_limiter->TryUseRate(kRateFillingBytes / 2));
+
+  // 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(kRateFillingBytes + 1));
+}
+
+}  // namespace webrtc