Add CopyOnWriteBuffer class

webrtc/base/buffer_unittest.cc

Index: webrtc/base/buffer_unittest.cc
diff --git a/webrtc/base/buffer_unittest.cc b/webrtc/base/buffer_unittest.cc
index 0b93b9b56e8d54afdd4b5d89964023f75c0cbb5f..a1f97d71151e657ef063467e897dd621de2e2f6f 100644
--- a/webrtc/base/buffer_unittest.cc
+++ b/webrtc/base/buffer_unittest.cc
@@ -177,4 +177,108 @@ TEST(BufferTest, TestSwap) {
   EXPECT_EQ(buf2.data(), data1);
 }
 
+void EnsureBuffersEqual(const Buffer& buf1, const Buffer& buf2) {
+  // Data is shared between buffers.
+  EXPECT_EQ(buf1.size(), buf2.size());
+  EXPECT_EQ(buf1.capacity(), buf2.capacity());
+  const uint8_t* data1 = buf1.data();
+  const uint8_t* data2 = buf2.data();
+  EXPECT_EQ(data1, data2);
+  EXPECT_EQ(buf1, buf2);
+}
+
+// Move comparison to own function to have const buffers and prevent cloning
+// from calling non-const "data()".
+void EnsureBufferDataNotEqual(const Buffer& buf1, const Buffer& buf2) {
+  // Data is not shared between buffers.
+  const uint8_t* data1 = buf1.data();
+  const uint8_t* data2 = buf2.data();
+  EXPECT_NE(data1, data2);
+}
+
+TEST(BufferTest, TestSharedAppendData) {
+  Buffer buf1(kTestData, 3, 10);
+  Buffer buf2(buf1);
+
+  EnsureBuffersEqual(buf1, buf2);
+
+  // AppendData copies the underlying buffer.
+  buf2.AppendData("foo");
+  EXPECT_EQ(buf2.size(), buf1.size() + 4);  // "foo" + trailing 0x00
+  EXPECT_EQ(buf2.capacity(), buf1.capacity());
+  EXPECT_NE(buf2.data(), buf1.data());
+
+  EXPECT_EQ(buf1, Buffer(kTestData, 3));
+  const int8_t exp[] = {0x0, 0x1, 0x2, 'f', 'o', 'o', 0x0};
+  EXPECT_EQ(buf2, Buffer(exp));
+}
+
+TEST(BufferTest, TestSharedSetData) {
+  Buffer buf1(kTestData, 3, 10);
+  Buffer buf2;
+
+  buf2.SetData(buf1);
+  // buf2 shares the same data as buf1 now.
+  EnsureBuffersEqual(buf1, buf2);
+
+  Buffer buf3(buf1);
+  // buf3 is re-allocated with new data, existing buffers are not modified.
+  buf3.SetData("foo");
+  EXPECT_EQ(buf1, Buffer(kTestData, 3));
+  EnsureBuffersEqual(buf1, buf2);
+  EnsureBufferDataNotEqual(buf1, buf3);
+  const int8_t exp[] = {'f', 'o', 'o', 0x0};
+  EXPECT_EQ(buf3, Buffer(exp));
+}
+
+TEST(BufferTest, TestSharedEnsureCapacity) {
+  Buffer buf1(kTestData, 3, 10);
+  Buffer buf2(buf1);
+
+  // Smaller than existing capacity -> no change and still same contents.
+  buf2.EnsureCapacity(8);
+  EnsureBuffersEqual(buf1, buf2);
+  EXPECT_EQ(buf1.size(), 3u);
+  EXPECT_EQ(buf1.capacity(), 10u);
+  EXPECT_EQ(buf2.size(), 3u);
+  EXPECT_EQ(buf2.capacity(), 10u);
+
+  // Lager than existing capacity -> data is cloned.
+  buf2.EnsureCapacity(16);
+  EnsureBufferDataNotEqual(buf1, buf2);
+  EXPECT_EQ(buf1.size(), 3u);
+  EXPECT_EQ(buf1.capacity(), 10u);
+  EXPECT_EQ(buf2.size(), 3u);
+  EXPECT_EQ(buf2.capacity(), 16u);
+  // The size and contents are still the same.
+  EXPECT_EQ(buf1, buf2);
+}
+
+TEST(BufferTest, TestSharedSetSize) {
+  Buffer buf1(kTestData, 3, 10);
+  Buffer buf2(buf1);
+
+  buf2.SetSize(16);
+  EnsureBufferDataNotEqual(buf1, buf2);
+  EXPECT_EQ(buf1.size(), 3u);
+  EXPECT_EQ(buf1.capacity(), 10u);
+  EXPECT_EQ(buf2.size(), 16u);
+  EXPECT_EQ(buf2.capacity(), 16u);
+  // The contents got cloned.
+  EXPECT_EQ(0, memcmp(buf2.data(), kTestData, 3));
+}
+
+TEST(BufferTest, TestSharedClear) {
+  Buffer buf1(kTestData, 3, 10);
+  Buffer buf2(buf1);
+
+  buf2.Clear();
+  EnsureBufferDataNotEqual(buf1, buf2);
+  EXPECT_EQ(buf1.size(), 3u);
+  EXPECT_EQ(buf1.capacity(), 10u);
+  EXPECT_EQ(0, memcmp(buf1.data(), kTestData, 3));
+  EXPECT_EQ(buf2.size(), 0u);
+  EXPECT_EQ(buf2.capacity(), 0u);
+}
+
 }  // namespace rtc