Add CopyOnWriteBuffer class

webrtc/base/copyonwritebuffer_unittest.cc

Index: webrtc/base/copyonwritebuffer_unittest.cc
diff --git a/webrtc/base/copyonwritebuffer_unittest.cc b/webrtc/base/copyonwritebuffer_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a95ad67a03e6ec2c41ad1210d3ae241f590ed3e7
--- /dev/null
+++ b/webrtc/base/copyonwritebuffer_unittest.cc
@@ -0,0 +1,199 @@
+/*
+ *  Copyright 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 "webrtc/base/copyonwritebuffer.h"
+#include "webrtc/base/gunit.h"
+
+namespace rtc {
+
+namespace {
+
+// clang-format off
+const uint8_t kTestData[] = {0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7,
+                             0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf};
+// clang-format on
+
+}  // namespace
+
+void EnsureBuffersShareData(const CopyOnWriteBuffer& buf1,
+                            const CopyOnWriteBuffer& 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);
+}
+
+void EnsureBuffersDontShareData(const CopyOnWriteBuffer& buf1,
+                                const CopyOnWriteBuffer& buf2) {
+  // Data is not shared between buffers.
+  const uint8_t* data1 = buf1.cdata();
+  const uint8_t* data2 = buf2.cdata();
+  EXPECT_NE(data1, data2);
+}
+
+TEST(CopyOnWriteBufferTest, TestMoveConstruct) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  size_t buf1_size = buf1.size();
+  size_t buf1_capacity = buf1.capacity();
+  const uint8_t* buf1_data = buf1.cdata();
+
+  CopyOnWriteBuffer buf2(std::move(buf1));
+  EXPECT_EQ(buf1.size(), 0u);
+  EXPECT_EQ(buf1.capacity(), 0u);
+  EXPECT_EQ(buf1.data(), nullptr);
+  EXPECT_EQ(buf2.size(), buf1_size);
+  EXPECT_EQ(buf2.capacity(), buf1_capacity);
+  EXPECT_EQ(buf2.data(), buf1_data);
+}
+
+TEST(CopyOnWriteBufferTest, TestMoveAssign) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  size_t buf1_size = buf1.size();
+  size_t buf1_capacity = buf1.capacity();
+  const uint8_t* buf1_data = buf1.cdata();
+
+  CopyOnWriteBuffer buf2;
+  buf2 = std::move(buf1);
+  EXPECT_EQ(buf1.size(), 0u);
+  EXPECT_EQ(buf1.capacity(), 0u);
+  EXPECT_EQ(buf1.data(), nullptr);
+  EXPECT_EQ(buf2.size(), buf1_size);
+  EXPECT_EQ(buf2.capacity(), buf1_capacity);
+  EXPECT_EQ(buf2.data(), buf1_data);
+}
+
+TEST(CopyOnWriteBufferTest, TestSwap) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  size_t buf1_size = buf1.size();
+  size_t buf1_capacity = buf1.capacity();
+  const uint8_t* buf1_data = buf1.cdata();
+
+  CopyOnWriteBuffer buf2(kTestData, 6, 20);
+  size_t buf2_size = buf2.size();
+  size_t buf2_capacity = buf2.capacity();
+  const uint8_t* buf2_data = buf2.cdata();
+
+  std::swap(buf1, buf2);
+  EXPECT_EQ(buf1.size(), buf2_size);
+  EXPECT_EQ(buf1.capacity(), buf2_capacity);
+  EXPECT_EQ(buf1.data(), buf2_data);
+  EXPECT_EQ(buf2.size(), buf1_size);
+  EXPECT_EQ(buf2.capacity(), buf1_capacity);
+  EXPECT_EQ(buf2.data(), buf1_data);
+}
+
+TEST(CopyOnWriteBufferTest, TestAppendData) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  CopyOnWriteBuffer buf2(buf1);
+
+  EnsureBuffersShareData(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, CopyOnWriteBuffer(kTestData, 3));
+  const int8_t exp[] = {0x0, 0x1, 0x2, 'f', 'o', 'o', 0x0};
+  EXPECT_EQ(buf2, CopyOnWriteBuffer(exp));
+}
+
+TEST(CopyOnWriteBufferTest, TestSetData) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  CopyOnWriteBuffer buf2;
+
+  buf2.SetData(buf1);
+  // buf2 shares the same data as buf1 now.
+  EnsureBuffersShareData(buf1, buf2);
+
+  CopyOnWriteBuffer buf3(buf1);
+  // buf3 is re-allocated with new data, existing buffers are not modified.
+  buf3.SetData("foo");
+  EXPECT_EQ(buf1, CopyOnWriteBuffer(kTestData, 3));
+  EnsureBuffersShareData(buf1, buf2);
+  EnsureBuffersDontShareData(buf1, buf3);
+  const int8_t exp[] = {'f', 'o', 'o', 0x0};
+  EXPECT_EQ(buf3, CopyOnWriteBuffer(exp));
+}
+
+TEST(CopyOnWriteBufferTest, TestEnsureCapacity) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  CopyOnWriteBuffer buf2(buf1);
+
+  // Smaller than existing capacity -> no change and still same contents.
+  buf2.EnsureCapacity(8);
+  EnsureBuffersShareData(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);
+  EnsureBuffersDontShareData(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(CopyOnWriteBufferTest, TestSetSize) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  CopyOnWriteBuffer buf2(buf1);
+
+  buf2.SetSize(16);
+  EnsureBuffersDontShareData(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(CopyOnWriteBufferTest, TestClear) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  CopyOnWriteBuffer buf2(buf1);
+
+  buf2.Clear();
+  EnsureBuffersDontShareData(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);
+}
+
+TEST(CopyOnWriteBufferTest, TestConstDataAccessor) {
+  CopyOnWriteBuffer buf1(kTestData, 3, 10);
+  CopyOnWriteBuffer buf2(buf1);
+
+  // .cdata() doesn't clone data.
+  const uint8_t* cdata1 = buf1.cdata();
+  const uint8_t* cdata2 = buf2.cdata();
+  EXPECT_EQ(cdata1, cdata2);
+
+  // Non-const .data() clones data if shared.
+  const uint8_t* data1 = buf1.data();
+  const uint8_t* data2 = buf2.data();
+  EXPECT_NE(data1, data2);
+  // buf1 was cloned above.
+  EXPECT_NE(data1, cdata1);
+  // Therefore buf2 was no longer sharing data and was not cloned.
+  EXPECT_EQ(data2, cdata1);
+}
+
+}  // namespace rtc