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      1 /*
      2  * Copyright (C) 2014 Square, Inc.
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 package com.squareup.okhttp.internal.spdy;
     17 
     18 import java.io.IOException;
     19 import java.util.List;
     20 import okio.BufferedSource;
     21 
     22 /**
     23  * {@link com.squareup.okhttp.Protocol#HTTP_2 HTTP/2} only.
     24  * Processes server-initiated HTTP requests on the client.
     25  *
     26  * <p>Use the stream ID to correlate response headers and data.
     27  *
     28  * <p>Return true to request cancellation of a pushed stream.  Note that this
     29  * does not guarantee future frames won't arrive on the stream ID.
     30  */
     31 public interface PushObserver {
     32   /**
     33    * Describes the request that the server intends to push a response for.
     34    *
     35    * @param streamId server-initiated stream ID: an even number.
     36    * @param requestHeaders minimally includes {@code :method}, {@code :scheme},
     37    * {@code :authority}, and (@code :path}.
     38    */
     39   boolean onRequest(int streamId, List<Header> requestHeaders);
     40 
     41   /**
     42    * The response headers corresponding to a pushed request.  When {@code last}
     43    * is true, there are no data frames to follow.
     44    *
     45    * @param streamId server-initiated stream ID: an even number.
     46    * @param responseHeaders minimally includes {@code :status}.
     47    * @param last when true, there is no response data.
     48    */
     49   boolean onHeaders(int streamId, List<Header> responseHeaders, boolean last);
     50 
     51   /**
     52    * A chunk of response data corresponding to a pushed request.  This data
     53    * must either be read or skipped.
     54    *
     55    * @param streamId server-initiated stream ID: an even number.
     56    * @param source location of data corresponding with this stream ID.
     57    * @param byteCount number of bytes to read or skip from the source.
     58    * @param last when true, there are no data frames to follow.
     59    */
     60   boolean onData(int streamId, BufferedSource source, int byteCount, boolean last)
     61       throws IOException;
     62 
     63   /** Indicates the reason why this stream was cancelled. */
     64   void onReset(int streamId, ErrorCode errorCode);
     65 
     66   PushObserver CANCEL = new PushObserver() {
     67 
     68     @Override public boolean onRequest(int streamId, List<Header> requestHeaders) {
     69       return true;
     70     }
     71 
     72     @Override public boolean onHeaders(int streamId, List<Header> responseHeaders, boolean last) {
     73       return true;
     74     }
     75 
     76     @Override public boolean onData(int streamId, BufferedSource source, int byteCount,
     77         boolean last) throws IOException {
     78       source.skip(byteCount);
     79       return true;
     80     }
     81 
     82     @Override public void onReset(int streamId, ErrorCode errorCode) {
     83     }
     84   };
     85 }
     86