tracing v2: Add ScatteredStreamWriter

components/tracing/core/scattered_stream_writer_unittest.cc

+// Copyright 2016 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 "components/tracing/core/scattered_stream_writer.h"
+
+#include <string.h>
+
+#include <memory>
+#include <vector>
+
+#include "base/strings/string_number_conversions.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace tracing {
+namespace v2 {
+namespace {
+
+class MockDelegate : public ScatteredStreamWriter::Delegate {
+ public:
+  static const size_t kChunkSize = 8;
+
+  ContiguousMemoryRange GetNewBuffer() override {
+    std::unique_ptr<uint8_t[]> chunk(new uint8_t[kChunkSize]);
+    uint8_t* begin = chunk.get();
+    memset(begin, 0, kChunkSize);
+    chunks.push_back(std::move(chunk));
+    return {begin, begin + kChunkSize};
+  }
+
+  std::string GetChunkAsString(int chunk_index) {
+    return base::HexEncode(chunks[chunk_index].get(), kChunkSize);
+  }
+
+  std::vector<std::unique_ptr<uint8_t[]>> chunks;
+};
+
+TEST(ScatteredStreamWriterTest, ScatteredWrites) {
+  MockDelegate delegate;
+  ScatteredStreamWriter ssw(&delegate);
+
+  const uint8_t kOneByteBuf[] = {0x40};
+  const uint8_t kThreeByteBuf[] = {0x50, 0x51, 0x52};
+  const uint8_t kFourByteBuf[] = {0x60, 0x61, 0x62, 0x63};
+  uint8_t kTwentyByteBuf[20];
+  for (uint8_t i = 0; i < sizeof(kTwentyByteBuf); ++i)
+    kTwentyByteBuf[i] = 0xA0 + i;
+
+  // Writing up to the chunk size should cause only the initial extension.
+  for (uint8_t i = 0; i < MockDelegate::kChunkSize; ++i) {
+    ssw.WriteByte(i);
+    EXPECT_EQ(MockDelegate::kChunkSize - i - 1, ssw.bytes_available());
+  }
+  EXPECT_EQ(1u, delegate.chunks.size());
+  EXPECT_EQ(0u, ssw.bytes_available());
+
+  // This extra write will cause the first extension.
+  ssw.WriteBytes(kOneByteBuf, sizeof(kOneByteBuf));
+  EXPECT_EQ(2u, delegate.chunks.size());
+  EXPECT_EQ(7u, ssw.bytes_available());
+
+  // This starts at offset 1, to make sure we don't hardcode any assumption
+  // about alignment.
+  ContiguousMemoryRange reserved_range_1 = ssw.ReserveBytes(4);
+  EXPECT_EQ(2u, delegate.chunks.size());
+  EXPECT_EQ(3u, ssw.bytes_available());
+
+  ssw.WriteByte(0xFF);
+  ssw.WriteBytes(kThreeByteBuf, sizeof(kThreeByteBuf));
+  EXPECT_EQ(3u, delegate.chunks.size());
+  EXPECT_EQ(7u, ssw.bytes_available());
+
+  ContiguousMemoryRange reserved_range_2 = ssw.ReserveBytes(4);
+  ssw.WriteBytes(kTwentyByteBuf, sizeof(kTwentyByteBuf));
+  EXPECT_EQ(6u, delegate.chunks.size());
+  EXPECT_EQ(7u, ssw.bytes_available());
+
+  // Writing reserved bytes should not change the bytes_available().
+  memcpy(reserved_range_1.begin, kFourByteBuf, sizeof(kFourByteBuf));
+  memcpy(reserved_range_2.begin, kFourByteBuf, sizeof(kFourByteBuf));
+  EXPECT_EQ(6u, delegate.chunks.size());
+  EXPECT_EQ(7u, ssw.bytes_available());
+
+  // Check that reserving more bytes than what left creates a brand new chunk
+  // even if the previous one is not exhausted
+  for (uint8_t i = 0; i < 5; ++i)
+    ssw.WriteByte(0xFF);
+  memcpy(ssw.ReserveBytes(4).begin, kFourByteBuf, sizeof(kFourByteBuf));
+  EXPECT_EQ(7u, delegate.chunks.size());
+  EXPECT_EQ(4u, ssw.bytes_available());
+
+  EXPECT_EQ("0001020304050607", delegate.GetChunkAsString(0));
+  EXPECT_EQ("4060616263FF5051", delegate.GetChunkAsString(1));
+  EXPECT_EQ("5260616263A0A1A2", delegate.GetChunkAsString(2));
+  EXPECT_EQ("A3A4A5A6A7A8A9AA", delegate.GetChunkAsString(3));
+  EXPECT_EQ("ABACADAEAFB0B1B2", delegate.GetChunkAsString(4));
+  EXPECT_EQ("B3FFFFFFFFFF0000", delegate.GetChunkAsString(5));
+  EXPECT_EQ("6061626300000000", delegate.GetChunkAsString(6));
+
+  // Finally reset the writer to a new buffer.
+  uint8_t other_buffer[8] = {0};
+  ssw.Reset({other_buffer, other_buffer + sizeof(other_buffer)});
+  EXPECT_EQ(other_buffer, ssw.write_ptr());
+  ssw.WriteByte(1);
+  ssw.WriteBytes(kThreeByteBuf, sizeof(kThreeByteBuf));
+  EXPECT_EQ(1u, other_buffer[0]);
+  EXPECT_EQ(0x52u, other_buffer[3]);
+}
+
+}  // namespace
+}  // namespace v2
+}  // namespace tracing