Replace uses of raw uint32's with a type-checked RtpTimeTicks data type.

media/cast/common/expanded_value_base_unittest.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/cast/common/expanded_value_base.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+namespace cast {
+
+namespace {
+
+// A basic subclass of ExpandedValueBase to use for testing.
+class TestValue : public ExpandedValueBase<int64_t, TestValue> {
+ public:
+  explicit TestValue(int64_t value) : ExpandedValueBase(value) {}
+};
+
+}  // namespace
+
+// Tests the various scenarios of truncating and then re-expanding values, and
+// confirming the correct behavior.  Note that, while the code below just tests
+// truncation/expansion to/from 8 bits, the 16- and 32-bit cases are implicitly
+// confirmed because the Expand() method uses the compiler to derive all of its
+// constants (based on the type of its argument).
+TEST(ExpandedValueBaseTest, TruncationAndExpansion) {
+  // Test that expansion works when the reference is always equal to the value
+  // that was truncated.
+  for (int64_t i = -512; i <= 512; ++i) {
+    const TestValue original_value(i);
+    const uint8_t truncated = original_value.lower_8_bits();
+    const TestValue reference(i);
+    ASSERT_EQ(original_value, reference.Expand(truncated)) << "i=" << i;
+  }
+
+  // Test that expansion works when the reference is always one less than the
+  // value that was truncated.
+  for (int64_t i = -512; i <= 512; ++i) {
+    const TestValue original_value(i);
+    const uint8_t truncated = original_value.lower_8_bits();
+    const TestValue reference(i - 1);
+    ASSERT_EQ(original_value, reference.Expand(truncated)) << "i=" << i;
+  }
+
+  // Test that expansion works when the reference is always one greater than the
+  // value that was truncated.
+  for (int64_t i = -512; i <= 512; ++i) {
+    const TestValue original_value(i);
+    const uint8_t truncated = original_value.lower_8_bits();
+    const TestValue reference(i + 1);
+    ASSERT_EQ(original_value, reference.Expand(truncated)) << "i=" << i;
+  }
+
+  // Test the cases where a difference of [-128,+127] around a fixed refererence
+  // does not trigger any wrap-around adjustments during expansion.
+  for (int64_t bias = -5; bias <= 5; ++bias) {
+    for (int64_t i = -128; i <= 127; ++i) {
+      const TestValue original_value(bias + i);
+      const uint8_t truncated = original_value.lower_8_bits();
+      const TestValue reference(bias);
+      ASSERT_EQ(original_value, reference.Expand(truncated)) << "bias=" << bias
+                                                             << ", i=" << i;
+    }
+  }
+
+  // Test the cases where a difference of [+128,+255] around a fixed reference
+  // always triggers backwards wrap-around adjustments.
+  for (int64_t bias = -5; bias <= 5; ++bias) {
+    for (int64_t i = 128; i <= 255; ++i) {
+      const TestValue original_value(bias + i - 256);

[Irfan, 2015/12/09 21:24:27]

am a little confused by the need for -256. perhaps explain here.

[miu, 2015/12/10 00:38:36]

I clarified with comments and a little extra code.  I think calling out
"wrap-around" in the comments made things confusing.  The logic is all about
finding the closest value to |reference| whose lower 8-bits match |truncated|.

+      const uint8_t truncated = original_value.lower_8_bits();
+      const TestValue reference(bias);
+      ASSERT_EQ(original_value, reference.Expand(truncated)) << "bias=" << bias
+                                                             << ", i=" << i;
+    }
+  }
+
+  // Test the cases where a difference of [-256,-129] around a fixed reference
+  // always triggers forwards wrap-around adjustments.
+  for (int64_t bias = -5; bias <= 5; ++bias) {
+    for (int64_t i = -256; i <= -129; ++i) {
+      const TestValue original_value(bias + i + 256);
+      const uint8_t truncated = original_value.lower_8_bits();
+      const TestValue reference(bias);
+      ASSERT_EQ(original_value, reference.Expand(truncated)) << "bias=" << bias
+                                                             << ", i=" << i;
+    }
+  }
+}
+
+}  // namespace cast
+}  // namespace media