tracing v2: Introduce TraceBufferReader to read-back the trace buffer

components/tracing/core/trace_buffer_reader_unittest.cc

Index: components/tracing/core/trace_buffer_reader_unittest.cc
diff --git a/components/tracing/core/trace_buffer_reader_unittest.cc b/components/tracing/core/trace_buffer_reader_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8a4210b99104ac5185ed142412a20d1919be0a78
--- /dev/null
+++ b/components/tracing/core/trace_buffer_reader_unittest.cc
@@ -0,0 +1,227 @@
+// 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/trace_buffer_reader.h"
+
+#include "base/macros.h"
+#include "base/memory/ptr_util.h"
+#include "components/tracing/core/string_interning.h"
+#include "components/tracing/test/golden_protos/event.pb.h"
+#include "components/tracing/test/golden_protos/events_chunk.pb.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace tracing {
+namespace v2 {
+namespace {
+
+namespace golden_protos = ::tracing::proto;
+
+::testing::AssertionResult ValueEquals(const char* m_expr,
+                                       const char* n_expr,
+                                       const base::Value& m,
+                                       const base::Value& n) {
+  if (m.Equals(&n))
+    return ::testing::AssertionSuccess();
+
+  return ::testing::AssertionFailure() << "\nExpected:\n"
+                                       << m << "\nActual:\n"
+                                       << n;
+}
+
+void ParseChunk(TraceBufferReader* reader, const std::string& chunk) {
+  reader->ParseChunk(reinterpret_cast<const uint8_t*>(chunk.data()),
+                     chunk.size());
+}
+
+// Parse a zero length chunk and a chunk with no events. In both cases parsing
+// should succeed but no event should be decoded.
+TEST(TraceBufferReaderTest, EmptyChunk) {
+  golden_protos::EventsChunk chunk;
+  chunk.set_writer_id(1);
+  chunk.set_seq_id(0);
+
+  TraceBufferReader reader(TraceBufferReader::kBuildLegacyJSONEvents);
+  std::string zero_len_chunk;
+  ParseChunk(&reader, zero_len_chunk);
+  ParseChunk(&reader, chunk.SerializeAsString());
+  ASSERT_EQ(0u, reader.legacy_events()->GetSize());
+}
+
+TEST(TraceBufferReaderTest, OneChunkOneEvent) {
+  golden_protos::Event evt;
+  evt.set_type(golden_protos::Event::COMPLETE);
+  evt.set_name_str("copied_str_name");
+  auto interned_cat_name = InternString("interned_category_name");
+  evt.set_category_id(interned_cat_name);
+  evt.set_timestamp(42);
+  evt.set_thread_timestamp(0xf1f2f3f4);
+
+  golden_protos::EventsChunk chunk;
+  chunk.set_writer_id(1);
+  chunk.set_seq_id(0);
+  chunk.add_events(evt.SerializeAsString());
+
+  TraceBufferReader reader(TraceBufferReader::kBuildLegacyJSONEvents |
+                           TraceBufferReader::kBuildInternedStringsTable);
+  ParseChunk(&reader, chunk.SerializeAsString());
+  ASSERT_EQ(1u, reader.legacy_events()->GetSize());
+  base::DictionaryValue* decoded_evt = nullptr;
+  ASSERT_TRUE(reader.legacy_events()->GetDictionary(0, &decoded_evt));
+
+  base::DictionaryValue expected_value;
+  expected_value.SetString("ph", "X");
+  expected_value.SetString("name", "copied_str_name");
+  expected_value.SetString("cat", "interned_category_name");
+  expected_value.SetInteger("ts", 42);
+  expected_value.SetInteger("tts", static_cast<int>(0xf1f2f3f4));
+  EXPECT_PRED_FORMAT2(ValueEquals, expected_value, *decoded_evt);
+
+  ASSERT_EQ(1u, reader.interned_strings().count(interned_cat_name));
+  EXPECT_EQ("interned_category_name",
+            reader.interned_strings().at(interned_cat_name));
+}
+
+TEST(TraceBufferReaderTest, OneChunkManyEvents) {
+  golden_protos::EventsChunk chunk;
+  chunk.set_writer_id(1);
+  chunk.set_seq_id(42);
+  const char* kCatNames[] = {"cat1", "cat2", "cat3", "cat4"};
+  const size_t kNumEvents = 100;
+
+  for (size_t i = 0; i < kNumEvents; ++i) {
+    golden_protos::Event evt;
+    evt.set_type(golden_protos::Event::COMPLETE);
+    evt.set_name_str("copied_str_name");
+    evt.set_category_id(InternString(kCatNames[i % arraysize(kCatNames)]));
+    evt.set_timestamp(0xff000000 + i);
+    chunk.add_events(evt.SerializeAsString());
+  }
+
+  TraceBufferReader reader(TraceBufferReader::kBuildLegacyJSONEvents |
+                           TraceBufferReader::kBuildInternedStringsTable);
+  ParseChunk(&reader, chunk.SerializeAsString());
+  ASSERT_EQ(kNumEvents, reader.legacy_events()->GetSize());
+  for (size_t i = 0; i < kNumEvents; ++i) {
+    base::DictionaryValue* decoded_evt = nullptr;
+    ASSERT_TRUE(reader.legacy_events()->GetDictionary(i, &decoded_evt));
+    base::DictionaryValue expected_value;
+    expected_value.SetString("ph", "X");
+    expected_value.SetString("name", "copied_str_name");
+    expected_value.SetString("cat", kCatNames[i % arraysize(kCatNames)]);
+    expected_value.SetInteger("ts", static_cast<int>(0xff000000 + i));
+    ASSERT_PRED_FORMAT2(ValueEquals, expected_value, *decoded_evt);
+  }
+}
+
+// Test the decoding events that are fragmented across multiple chunks.
+TEST(TraceBufferReaderTest, FragmentedEvents) {
+  golden_protos::Event evt[3];
+  for (size_t i = 0; i < arraysize(evt); ++i) {
+    evt[i].set_type(golden_protos::Event::COMPLETE);
+    evt[i].set_name_str("copied_str_name");
+    evt[i].set_category_id(InternString("interned_category_name"));
+    evt[i].set_timestamp(i);
+  }
+
+  // The 2nd event (evt[1]) will be split into three fragments and distributed
+  // over all three chunks.
+  const size_t evt1_size = evt[1].ByteSize();
+  DCHECK_GT(evt1_size, 8u);
+  std::unique_ptr<uint8_t[]> serialized_evt1(new uint8_t[evt1_size]);
+  evt[1].SerializeToArray(serialized_evt1.get(), evt1_size);
+
+  // Create three chunks and split the three events as follows:
+  // chunk[0]: evt[0] (full), evt[1] (fragment 1/3)
+  // chunk[1]: evt[1] (fragment 2/3)
+  // chunk[2]: evt[1] (fragment 3/3), evt[2] (full)
+
+  golden_protos::EventsChunk chunk[3];
+  for (size_t i = 0; i < arraysize(chunk); ++i) {
+    chunk[i].set_writer_id(42);
+    chunk[i].set_seq_id(i);
+  }
+
+  chunk[0].set_first_event_continues_from_prev_chunk(false);
+  chunk[0].set_last_event_continues_on_next_chunk(true);
+  chunk[0].add_events(evt[0].SerializeAsString());
+  chunk[0].add_events(&serialized_evt1[0], 4);
+
+  chunk[1].set_first_event_continues_from_prev_chunk(true);
+  chunk[1].set_last_event_continues_on_next_chunk(true);
+  chunk[1].add_events(&serialized_evt1[4], 4);
+
+  chunk[2].set_first_event_continues_from_prev_chunk(true);
+  chunk[2].add_events(&serialized_evt1[8], evt1_size - 8);
+  chunk[2].add_events(evt[2].SerializeAsString());
+
+  TraceBufferReader reader(TraceBufferReader::kBuildLegacyJSONEvents |
+                           TraceBufferReader::kBuildInternedStringsTable);
+  for (size_t i = 0; i < arraysize(chunk); ++i)
+    ParseChunk(&reader, chunk[i].SerializeAsString());
+
+  ASSERT_EQ(arraysize(evt), reader.legacy_events()->GetSize());
+  for (size_t i = 0; i < arraysize(evt); ++i) {
+    base::DictionaryValue* decoded_evt = nullptr;
+    ASSERT_TRUE(reader.legacy_events()->GetDictionary(i, &decoded_evt));
+
+    base::DictionaryValue expected_value;
+    expected_value.SetString("ph", "X");
+    expected_value.SetString("name", "copied_str_name");
+    expected_value.SetString("cat", "interned_category_name");
+    expected_value.SetInteger("ts", static_cast<int>(i));
+    ASSERT_PRED_FORMAT2(ValueEquals, expected_value, *decoded_evt);
+  }
+}
+
+// Test that the fragment reconstruction logic discards fragments if one of
+// the chunks is missing.
+TEST(TraceBufferReaderTest, FragmentedEventsWithMissingChunks) {
+  golden_protos::Event evt[2];
+  for (size_t i = 0; i < arraysize(evt); ++i) {
+    evt[i].set_type(golden_protos::Event::METADATA);
+    evt[i].set_timestamp(i);
+  }
+
+  golden_protos::EventsChunk chunk[2];
+  for (size_t i = 0; i < arraysize(chunk); ++i) {
+    chunk[i].set_writer_id(42);
+    chunk[i].set_seq_id(1 + i);
+  }
+
+  // The 2nd event (evt[1]) will be split into two fragments.
+  const size_t evt1_size = evt[1].ByteSize();
+  DCHECK_GT(evt1_size, 2u);
+  std::unique_ptr<uint8_t[]> serialized_evt1(new uint8_t[evt1_size]);
+  evt[1].SerializeToArray(serialized_evt1.get(), evt1_size);
+
+  chunk[0].set_first_event_continues_from_prev_chunk(true);
+  chunk[0].set_last_event_continues_on_next_chunk(true);
+  chunk[0].add_events("should be discarded because seq id 0 is not seen.");
+  chunk[0].add_events(evt[0].SerializeAsString());
+  chunk[0].add_events(&serialized_evt1[0], 2);
+
+  chunk[1].set_first_event_continues_from_prev_chunk(true);
+  chunk[1].set_last_event_continues_on_next_chunk(true);
+  chunk[1].add_events(&serialized_evt1[0] + 2, evt1_size - 2);
+  chunk[1].add_events("should be discarded because seq id 2 is not seen.");
+
+  TraceBufferReader reader(TraceBufferReader::kBuildLegacyJSONEvents);
+  ParseChunk(&reader, chunk[0].SerializeAsString());
+  ParseChunk(&reader, chunk[1].SerializeAsString());
+
+  ASSERT_EQ(arraysize(evt), reader.legacy_events()->GetSize());
+  for (size_t i = 0; i < arraysize(evt); ++i) {
+    base::DictionaryValue* decoded_evt = nullptr;
+    ASSERT_TRUE(reader.legacy_events()->GetDictionary(i, &decoded_evt));
+
+    base::DictionaryValue expected_value;
+    expected_value.SetString("ph", "M");
+    expected_value.SetInteger("ts", static_cast<int>(i));
+    ASSERT_PRED_FORMAT2(ValueEquals, expected_value, *decoded_evt);
+  }
+}
+
+}  // namespace
+}  // namespace v2
+}  // namespace tracing