Add TimestampUnwrapper and generalize the code

webrtc/modules/module_common_types_unittest.cc

 /*
  *  Copyright (c) 2013 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.
  */
 
@@ skipping 101 matching lines @@
   EXPECT_EQ(0x0000FFFFu, LatestTimestamp(0xFFFF0000, 0x0000FFFF));
 }
 
 
 TEST(SequenceNumberUnwrapper, Limits) {
   SequenceNumberUnwrapper unwrapper;
 
   EXPECT_EQ(0, unwrapper.Unwrap(0));
   EXPECT_EQ(0x8000, unwrapper.Unwrap(0x8000));
   // Delta is exactly 0x8000 but current is lower than input, wrap backwards.
-  EXPECT_EQ(0x0, unwrapper.Unwrap(0x0000));
+  EXPECT_EQ(0, unwrapper.Unwrap(0));
 
   EXPECT_EQ(0x8000, unwrapper.Unwrap(0x8000));
   EXPECT_EQ(0xFFFF, unwrapper.Unwrap(0xFFFF));
-  EXPECT_EQ(0x10000, unwrapper.Unwrap(0x0000));
+  EXPECT_EQ(0x10000, unwrapper.Unwrap(0));
   EXPECT_EQ(0xFFFF, unwrapper.Unwrap(0xFFFF));
   EXPECT_EQ(0x8000, unwrapper.Unwrap(0x8000));
   EXPECT_EQ(0, unwrapper.Unwrap(0));
 
   // Don't allow negative values.
   EXPECT_EQ(0xFFFF, unwrapper.Unwrap(0xFFFF));
 }
 
 TEST(SequenceNumberUnwrapper, ForwardWraps) {
   int64_t seq = 0;
@@ skipping 28 matching lines @@
   }
 
   seq = kNumWraps * 0xFFFF;
   unwrapper.UpdateLast(seq);
   for (; seq >= 0; --seq) {
     int64_t unwrapped = unwrapper.Unwrap(static_cast<uint16_t>(seq & 0xFFFF));
     EXPECT_EQ(seq, unwrapped);
   }
 }
 
+TEST(TimestampUnwrapper, Limits) {
+  TimestampUnwrapper unwrapper;
+
+  EXPECT_EQ(0, unwrapper.Unwrap(0));
+  EXPECT_EQ(0x80000000, unwrapper.Unwrap(0x80000000));
+  // Delta is exactly 0x80000000 but current is lower than input, wrap
+  // backwards.
+  EXPECT_EQ(0, unwrapper.Unwrap(0));
+
+  EXPECT_EQ(0x80000000, unwrapper.Unwrap(0x80000000));
+  EXPECT_EQ(0xFFFFFFFF, unwrapper.Unwrap(0xFFFFFFFF));
+  EXPECT_EQ(0x100000000, unwrapper.Unwrap(0x00000000));
+  EXPECT_EQ(0xFFFFFFFF, unwrapper.Unwrap(0xFFFFFFFF));
+  EXPECT_EQ(0x80000000, unwrapper.Unwrap(0x80000000));
+  EXPECT_EQ(0, unwrapper.Unwrap(0));
+
+  // Don't allow negative values.
+  EXPECT_EQ(0xFFFFFFFF, unwrapper.Unwrap(0xFFFFFFFF));
+}
+
+TEST(TimestampUnwrapper, ForwardWraps) {
+  int64_t ts = 0;
+  TimestampUnwrapper unwrapper;
+
+  const int64_t kMaxIncrease = 0x80000000 - 1;
+  const int kNumWraps = 4;
+  for (int i = 0; i < kNumWraps * 2; ++i) {
+    int64_t unwrapped =
+        unwrapper.Unwrap(static_cast<uint32_t>(ts & 0xFFFFFFFF));
+    EXPECT_EQ(ts, unwrapped);
+    ts += kMaxIncrease;
+  }
+}
+
+TEST(TimestampUnwrapper, BackwardWraps) {
+  TimestampUnwrapper unwrapper;
+
+  const int64_t kMaxDecrease = 0x80000000 - 1;
+  const int kNumWraps = 4;
+  int64_t ts = kNumWraps * 2 * kMaxDecrease;
+  unwrapper.UpdateLast(ts);
+  for (int i = 0; i <= kNumWraps * 2; ++i) {
+    int64_t unwrapped =
+        unwrapper.Unwrap(static_cast<uint32_t>(ts & 0xFFFFFFFF));
+    EXPECT_EQ(ts, unwrapped);
+    ts -= kMaxDecrease;
+  }
+}
+
 }  // namespace webrtc