tracing v2: refactor fake_scattered_buffer class for tests

components/tracing/test/fake_scattered_buffer.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/test/fake_scattered_buffer.h"
+
+#include <string.h>
+
+#include "base/strings/string_number_conversions.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace tracing {
+namespace v2 {
+
+FakeScatteredBuffer::FakeScatteredBuffer(size_t chunk_size)
+    : chunk_size_(chunk_size) {}
+
+FakeScatteredBuffer::~FakeScatteredBuffer() {}
+
+ContiguousMemoryRange FakeScatteredBuffer::GetNewBuffer() {
+  std::unique_ptr<uint8_t[]> chunk(new uint8_t[chunk_size_]);
+  uint8_t* begin = chunk.get();
+  memset(begin, 0, chunk_size_);
+  chunks_.push_back(std::move(chunk));
+  return {begin, begin + chunk_size_};
+}
+
+std::string FakeScatteredBuffer::GetChunkAsString(int chunk_index) {
+  return base::HexEncode(chunks_[chunk_index].get(), chunk_size_);
+}
+
+std::string FakeScatteredBuffer::GetBytesAsString(size_t start, size_t length) {
+  std::string hexstr;
+  EXPECT_LE(start + length, chunks_.size() * chunk_size_);
+  for (size_t pos = start; pos < start + length; ++pos) {
+    const size_t chunk_idx = pos / chunk_size_;
+    const size_t chunk_off = pos % chunk_size_;
+    if (chunk_idx >= chunks_.size()) {
+      hexstr += " <OUT OF BOUND @ pos=" + base::SizeTToString(pos) + ">";
+      return hexstr;
+    }
+    hexstr += base::HexEncode(&chunks_[chunk_idx].get()[chunk_off], 1);
+  }
+  return hexstr;
+}
+
+}  // namespace v2
+}  // namespace tracing