src/cobalt/trace_event/json_file_outputter.cc

/*
 * Copyright 2015 Google Inc. All Rights Reserved.
 *
 * 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 "cobalt/trace_event/json_file_outputter.h"

#include <string>

#include "base/logging.h"
#include "base/platform_file.h"

namespace cobalt {
namespace trace_event {

JSONFileOutputter::JSONFileOutputter(const FilePath& output_path)
    : output_path_(output_path),
      output_trace_event_call_count_(0),
      file_(base::kInvalidPlatformFileValue) {
  file_ = base::CreatePlatformFile(
      output_path,
      base::PLATFORM_FILE_CREATE_ALWAYS | base::PLATFORM_FILE_WRITE, NULL,
      NULL);
  if (GetError()) {
    DLOG(ERROR) << "Unable to open file for writing: " << output_path.value();
  } else {
    std::string header_text("{\"traceEvents\": [\n");
    Write(header_text.c_str(), header_text.size());
  }
}

JSONFileOutputter::~JSONFileOutputter() {
  if (GetError()) {
    DLOG(ERROR) << "An error occurred while writing to the output file: "
                << output_path_.value();
  } else {
    const char tail[] = "\n]}";
    Write(tail, strlen(tail));
  }
  Close();
}

void JSONFileOutputter::OutputTraceData(
    const scoped_refptr<base::RefCountedString>& event_string) {
  DCHECK(!GetError());

  // This function is usually called as a callback by
  // base::debug::TraceLog::Flush().  It may get called by Flush()
  // multiple times.
  if (output_trace_event_call_count_ != 0) {
    const char text[] = ",\n";
    Write(text, strlen(text));
  }
  const std::string& event_str = event_string->data();
  Write(event_str.c_str(), event_str.size());
  ++output_trace_event_call_count_;
}

void JSONFileOutputter::Write(const char* buffer, size_t length) {
  if (GetError()) {
    return;
  }

  int count = base::WritePlatformFileAtCurrentPos(file_, buffer, length);
  if (count < 0) {
    Close();
  }
}

void JSONFileOutputter::Close() {
  if (GetError()) {
    return;
  }

  base::ClosePlatformFile(file_);
  file_ = base::kInvalidPlatformFileValue;
}

}  // namespace trace_event
}  // namespace cobalt