content: /*
   * Copyright (C) 2011 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 com.cjj.volley;
  
  import android.annotation.TargetApi;
  import android.net.TrafficStats;
  import android.os.Build;
  import android.os.Process;
  
  import java.util.concurrent.BlockingQueue;
  
  /**
   * Provides a thread for performing network dispatch from a queue of requests.
   *
   * Requests added to the specified queue are processed from the network via a
   * specified {@link Network} interface. Responses are committed to cache, if
   * eligible, using a specified {@link Cache} interface. Valid responses and
   * errors are posted back to the caller via a {@link ResponseDelivery}.
   */
  public class NetworkDispatcher extends Thread {
      /** The queue of requests to service. */
      private final BlockingQueue<Request<?>> mQueue;
      /** The network interface for processing requests. */
      private final Network mNetwork;
      /** The cache to write to. */
      private final Cache mCache;
      /** For posting responses and errors. */
      private final ResponseDelivery mDelivery;
      /** Used for telling us to die. */
      private volatile boolean mQuit = false;
  
      /**
       * Creates a new network dispatcher thread.  You must call {@link #start()}
       * in order to begin processing.
       *
       * @param queue Queue of incoming requests for triage
       * @param network Network interface to use for performing requests
       * @param cache Cache interface to use for writing responses to cache
       * @param delivery Delivery interface to use for posting responses
       */
      public NetworkDispatcher(BlockingQueue<Request<?>> queue,
              Network network, Cache cache,
              ResponseDelivery delivery) {
          mQueue = queue;
          mNetwork = network;
          mCache = cache;
          mDelivery = delivery;
      }
  
      /**
       * Forces this dispatcher to quit immediately.  If any requests are still in
       * the queue, they are not guaranteed to be processed.
       */
      public void quit() {
          mQuit = true;
          interrupt();
      }
  
      @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
      private void addTrafficStatsTag(Request<?> request) {
          // Tag the request (if API >= 14)
          if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
              TrafficStats.setThreadStatsTag(request.getTrafficStatsTag());
          }
      }
  
      @Override
      public void run() {
          Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
          Request<?> request;
          while (true) {
              try {
                  // Take a request from the queue.
                  request = mQueue.take();
              } catch (InterruptedException e) {
                  // We may have been interrupted because it was time to quit.
                  if (mQuit) {
                      return;
                  }
                  continue;
              }
  
              try {
                  request.addMarker("network-queue-take");
  
                  // If the request was cancelled already, do not perform the
                  // network request.
                  if (request.isCanceled()) {
                      request.finish("network-discard-cancelled");
                      continue;
                  }
  
                  addTrafficStatsTag(request);
  
                  // Perform the network request.
                  NetworkResponse networkResponse = mNetwork.performRequest(request);
                  request.addMarker("network-http-complete");
  
                  // If the server returned 304 AND we delivered a response already,
                  // we're done -- don't deliver a second identical response.
                  if (networkResponse.notModified && request.hasHadResponseDelivered()) {
                      request.finish("not-modified");
                      continue;
                  }
  
                  // Parse the response here on the worker thread.
                  Response<?> response = request.parseNetworkResponse(networkResponse);
                  request.addMarker("network-parse-complete");
  
                  // Write to cache if applicable.
                  // TODO: Only update cache metadata instead of entire record for 304s.
                  if (request.shouldCache() && response.cacheEntry != null) {
                      mCache.put(request.getCacheKey(), response.cacheEntry);
                      request.addMarker("network-cache-written");
                  }
  
                  // Post the response back.
                  request.markDelivered();
                  mDelivery.postResponse(request, response);
              } catch (VolleyError volleyError) {
                  parseAndDeliverNetworkError(request, volleyError);
              } catch (Exception e) {
                  VolleyLog.e(e, "Unhandled exception %s", e.toString());
                  mDelivery.postError(request, new VolleyError(e));
              }
          }
      }
  
      private void parseAndDeliverNetworkError(Request<?> request, VolleyError error) {
          error = request.parseNetworkError(error);
          mDelivery.postError(request, error);
      }
  }
  