Android Open Source - Bolts-Android Bolts Executors

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License

The source code is released under:

BSD License For Bolts software Copyright (c) 2013, Facebook, Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that t...

Java Source Code

package bolts;
//from ww  w.  j a  v a2  s  .  com
import java.util.Locale;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;

/**
 * Collection of {@link Executor}s to use in conjunction with {@link Task}.
 */
/* package */ final class BoltsExecutors {

  private static final BoltsExecutors INSTANCE = new BoltsExecutors();

  private static boolean isAndroidRuntime() {
    String javaRuntimeName = System.getProperty("java.runtime.name");
    if (javaRuntimeName == null) {
      return false;
    }
    return javaRuntimeName.toLowerCase(Locale.US).contains("android");
  }

  private final ExecutorService background;
  private final Executor immediate;

  private BoltsExecutors() {
    background = !isAndroidRuntime()
        ? java.util.concurrent.Executors.newCachedThreadPool()
        : AndroidExecutors.newCachedThreadPool();
    immediate = new ImmediateExecutor();
  }

  /**
   * An {@link java.util.concurrent.Executor} that executes tasks in parallel.
   */
  public static ExecutorService background() {
    return INSTANCE.background;
  }

  /**
   * An {@link java.util.concurrent.Executor} that executes tasks in the current thread unless
   * the stack runs too deep, at which point it will delegate to {@link BoltsExecutors#background}
   * in order to trim the stack.
   */
  /* package */ static Executor immediate() {
    return INSTANCE.immediate;
  }

  /**
   * An {@link java.util.concurrent.Executor} that runs a runnable inline (rather than scheduling it
   * on a thread pool) as long as the recursion depth is less than MAX_DEPTH. If the executor has
   * recursed too deeply, it will instead delegate to the {@link Task#BACKGROUND_EXECUTOR} in order
   * to trim the stack.
   */
  private static class ImmediateExecutor implements Executor {
    private static final int MAX_DEPTH = 15;
    private ThreadLocal<Integer> executionDepth = new ThreadLocal<Integer>();

    /**
     * Increments the depth.
     *
     * @return the new depth value.
     */
    private int incrementDepth() {
      Integer oldDepth = executionDepth.get();
      if (oldDepth == null) {
        oldDepth = 0;
      }
      int newDepth = oldDepth + 1;
      executionDepth.set(newDepth);
      return newDepth;
    }

    /**
     * Decrements the depth.
     *
     * @return the new depth value.
     */
    private int decrementDepth() {
      Integer oldDepth = executionDepth.get();
      if (oldDepth == null) {
        oldDepth = 0;
      }
      int newDepth = oldDepth - 1;
      if (newDepth == 0) {
        executionDepth.remove();
      } else {
        executionDepth.set(newDepth);
      }
      return newDepth;
    }

    @Override
    public void execute(Runnable command) {
      int depth = incrementDepth();
      try {
        if (depth <= MAX_DEPTH) {
          command.run();
        } else {
          BoltsExecutors.background().execute(command);
        }
      } finally {
        decrementDepth();
      }
    }
  }
}

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