third_party/perfetto/src/tracing/core/trace_writer_for_testing.cc

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "src/tracing/core/trace_writer_for_testing.h"

#include "perfetto/base/logging.h"
#include "perfetto/ext/base/utils.h"
#include "perfetto/protozero/message.h"
#include "protos/perfetto/trace/trace.pbzero.h"
#include "protos/perfetto/trace/trace_packet.pbzero.h"

namespace perfetto {

TraceWriterForTesting::TraceWriterForTesting()
    : delegate_(4096, 4096), stream_(&delegate_) {
  delegate_.set_writer(&stream_);
  cur_packet_.reset(new protozero::RootMessage<protos::pbzero::TracePacket>());
  cur_packet_->Finalize();  // To avoid the DCHECK in NewTracePacket().
}

TraceWriterForTesting::~TraceWriterForTesting() {}

void TraceWriterForTesting::Flush(std::function<void()> callback) {
  // Flush() cannot be called in the middle of a TracePacket.
  PERFETTO_CHECK(cur_packet_->is_finalized());

  if (callback)
    callback();
}

std::vector<protos::gen::TracePacket>
TraceWriterForTesting::GetAllTracePackets() {
  PERFETTO_CHECK(cur_packet_->is_finalized());

  std::vector<uint8_t> buffer = delegate_.StitchSlices();
  protozero::ProtoDecoder trace(buffer.data(), buffer.size());
  std::vector<protos::gen::TracePacket> ret;
  for (auto fld = trace.ReadField(); fld.valid(); fld = trace.ReadField()) {
    PERFETTO_CHECK(fld.id() == protos::pbzero::Trace::kPacketFieldNumber);
    protos::gen::TracePacket packet;
    packet.ParseFromArray(fld.data(), fld.size());
    ret.emplace_back(std::move(packet));
  }
  PERFETTO_CHECK(trace.bytes_left() == 0);
  return ret;
}

protos::gen::TracePacket TraceWriterForTesting::GetOnlyTracePacket() {
  auto packets = GetAllTracePackets();
  PERFETTO_CHECK(packets.size() == 1);
  return packets[0];
}

TraceWriterForTesting::TracePacketHandle
TraceWriterForTesting::NewTracePacket() {
  // If we hit this, the caller is calling NewTracePacket() without having
  // finalized the previous packet.
  PERFETTO_DCHECK(cur_packet_->is_finalized());
  cur_packet_->Reset(&stream_);

  // Instead of storing the contents of the TracePacket directly in the backing
  // buffer like the real trace writers, we prepend the proto preamble to make
  // the buffer contents parsable as a sequence of TracePacket protos.

  uint8_t data[protozero::proto_utils::kMaxTagEncodedSize];
  uint8_t* data_end = protozero::proto_utils::WriteVarInt(
      protozero::proto_utils::MakeTagLengthDelimited(
          protos::pbzero::Trace::kPacketFieldNumber),
      data);
  stream_.WriteBytes(data, static_cast<uint32_t>(data_end - data));
  cur_packet_->set_size_field(
      stream_.ReserveBytes(protozero::proto_utils::kMessageLengthFieldSize));
  cur_packet_written_start_ = static_cast<size_t>(stream_.written());

  auto packet = TraceWriter::TracePacketHandle(cur_packet_.get());
  return packet;
}

void TraceWriterForTesting::FinishTracePacket() {
  // If the caller uses TakeStreamWriter(), cur_packet_->size() is not up to
  // date, only the stream writer knows the exact size.
  // cur_packet_->size_field() is still used to store the start of the packet.
  uint8_t* patch = cur_packet_->size_field();
  if (patch) {
    size_t size =
        static_cast<size_t>(stream_.written()) - cur_packet_written_start_;
    protozero::proto_utils::WriteRedundantVarInt(static_cast<uint32_t>(size),
                                                 patch);
  }
  cur_packet_->Reset(&stream_);
  cur_packet_->Finalize();  // To avoid the DCHECK in NewTracePacket().
}

WriterID TraceWriterForTesting::writer_id() const {
  return 0;
}

uint64_t TraceWriterForTesting::written() const {
  return 0;
}

}  // namespace perfetto