content: /*
   * Copyright (C) 2016 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.
   */
  
  package android.util;
  
  import android.os.Build;
  import android.os.SystemClock;
  import android.os.Trace;
  
  import java.util.ArrayDeque;
  import java.util.Deque;
  
  /**
   * Helper class for reporting boot and shutdown timing metrics.
   * <p>Note: This class is not thread-safe. Use a separate copy for other threads</p>
   * @hide
   */
  public class TimingsTraceLog {
      // Debug boot time for every step if it's non-user build.
      private static final boolean DEBUG_BOOT_TIME = !Build.IS_USER;
      private final Deque<Pair<String, Long>> mStartTimes =
              DEBUG_BOOT_TIME ? new ArrayDeque<>() : null;
      private final String mTag;
      private long mTraceTag;
      private long mThreadId;
  
      public TimingsTraceLog(String tag, long traceTag) {
          mTag = tag;
          mTraceTag = traceTag;
          mThreadId = Thread.currentThread().getId();
      }
  
      /**
       * Begin tracing named section
       * @param name name to appear in trace
       */
      public void traceBegin(String name) {
          assertSameThread();
          Trace.traceBegin(mTraceTag, name);
          if (DEBUG_BOOT_TIME) {
              mStartTimes.push(Pair.create(name, SystemClock.elapsedRealtime()));
          }
      }
  
      /**
       * End tracing previously {@link #traceBegin(String) started} section.
       * Also {@link #logDuration logs} the duration.
       */
      public void traceEnd() {
          assertSameThread();
          Trace.traceEnd(mTraceTag);
          if (!DEBUG_BOOT_TIME) {
              return;
          }
          if (mStartTimes.peek() == null) {
              Slog.w(mTag, "traceEnd called more times than traceBegin");
              return;
          }
          Pair<String, Long> event = mStartTimes.pop();
          logDuration(event.first, (SystemClock.elapsedRealtime() - event.second));
      }
  
      private void assertSameThread() {
          final Thread currentThread = Thread.currentThread();
          if (currentThread.getId() != mThreadId) {
              throw new IllegalStateException("Instance of TimingsTraceLog can only be called from "
                      + "the thread it was created on (tid: " + mThreadId + "), but was from "
                      + currentThread.getName() + " (tid: " + currentThread.getId() + ")");
          }
      }
  
      /**
       * Log the duration so it can be parsed by external tools for performance reporting
       */
      public void logDuration(String name, long timeMs) {
          Slog.d(mTag, name + " took to complete: " + timeMs + "ms");
      }
  }
  