tracing v2: refactor fake_scattered_buffer class for tests

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 "components/tracing/test/fake_scattered_buffer.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;
-};
+const size_t kChunkSize = 8;
 
 TEST(ScatteredStreamWriterTest, ScatteredWrites) {
-  MockDelegate delegate;
+  FakeScatteredBuffer delegate(kChunkSize);
   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) {
+  for (uint8_t i = 0; i < kChunkSize; ++i) {
     ssw.WriteByte(i);
-    EXPECT_EQ(MockDelegate::kChunkSize - i - 1, ssw.bytes_available());
+    EXPECT_EQ(kChunkSize - i - 1, ssw.bytes_available());
   }
-  EXPECT_EQ(1u, delegate.chunks.size());
+  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(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(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(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(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(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(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