[Android] Some clean up in pylib.

tools/android/device_stats_monitor/device_stats_monitor.cc

-// Copyright (c) 2012 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.
-
-// Dumps CPU and IO stats to a file at a regular interval.
-//
-// Output may be post processed by host to get top/iotop style information.
-
-#include <signal.h>
-#include <unistd.h>
-
-#include <fstream>
-#include <string>
-#include <vector>
-
-#include "base/command_line.h"
-#include "base/file_util.h"
-#include "base/strings/string_split.h"
-
-namespace {
-
-const char kIOStatsPath[] = "/proc/diskstats";
-const char kCPUStatsPath[] = "/proc/stat";
-
-class DeviceStatsMonitor {
- public:
-  explicit DeviceStatsMonitor(const std::string& out_path)
-      : out_path_(out_path),
-        record_(true) {
-    CHECK(!out_path_.empty());
-    samples_.reserve(1024 * 1024);
-  }
-
-  // Records stats continuously at |hz| cycles per second util
-  // StopRecordingAndDumpStats() is called.
-  //
-  // Yes, this buffers everything in memory, so it cannot be used for extended
-  // durations without OOM. But that beats writing during the trace which
-  // would affect the results.
-  void Start(int hz) {
-    const int sample_interval = 1000000 / hz;
-    const base::FilePath io_stats_path(kIOStatsPath);
-    const base::FilePath cpu_stats_path(kCPUStatsPath);
-    std::string out;
-    while (record_) {
-      out.clear();
-      CHECK(base::ReadFileToString(io_stats_path, &out));
-      CHECK(base::ReadFileToString(cpu_stats_path, &out));
-      samples_.push_back(out);
-      usleep(sample_interval);
-    }
-  }
-
-  // Stops recording and saves samples to file.
-  void StopAndDumpStats() {
-    record_ = false;
-    usleep(250 * 1000);
-    std::ofstream out_stream;
-    out_stream.open(out_path_.value().c_str(), std::ios::out);
-    for (std::vector<std::string>::const_iterator i = samples_.begin();
-         i != samples_.end(); ++i) {
-      out_stream << i->c_str() << std::endl;
-    }
-    out_stream.close();
-  }
-
- private:
-  const base::FilePath out_path_;
-  std::vector<std::string> samples_;
-  bool record_;
-
-  DISALLOW_COPY_AND_ASSIGN(DeviceStatsMonitor);
-};
-
-DeviceStatsMonitor* g_device_stats_monitor = NULL;
-
-void SigTermHandler(int unused) {
-  printf("Stopping device stats monitor\n");
-  g_device_stats_monitor->StopAndDumpStats();
-}
-
-}  // namespace
-
-int main(int argc, char** argv) {
-  const int kDefaultHz = 20;
-
-  CommandLine command_line(argc, argv);
-  CommandLine::StringVector args = command_line.GetArgs();
-  if (command_line.HasSwitch("h") || command_line.HasSwitch("help") ||
-      args.size() != 1) {
-    printf("Usage: %s OUTPUT_FILE\n"
-           "  --hz=HZ              Number of samples/second. default=%d\n",
-           argv[0], kDefaultHz);
-    return 1;
-  }
-
-  int hz = command_line.HasSwitch("hz") ?
-      atoi(command_line.GetSwitchValueNative("hz").c_str()) :
-      kDefaultHz;
-
-  printf("Starting device stats monitor\n");
-  g_device_stats_monitor = new DeviceStatsMonitor(args[0]);
-  signal(SIGTERM, SigTermHandler);
-  g_device_stats_monitor->Start(hz);
-  delete g_device_stats_monitor;
-
-  return 0;
-}