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 */
16package com.squareup.okhttp.internal.framed;
17
18import java.io.IOException;
19import java.util.List;
20import okio.BufferedSource;
21
22/**
23 * {@link com.squareup.okhttp.Protocol#HTTP_2 HTTP/2} only.
24 * Processes server-initiated HTTP requests on the client. Implementations must
25 * quickly dispatch callbacks to avoid creating a bottleneck.
26 *
27 * <p>While {@link #onReset} may occur at any time, the following callbacks are
28 * expected in order, correlated by stream ID.
29 * <ul>
30 *   <li>{@link #onRequest}</li>
31 *   <li>{@link #onHeaders} (unless canceled)</li>
32 *   <li>{@link #onData} (optional sequence of data frames)</li>
33 * </ul>
34 *
35 * <p>As a stream ID is scoped to a single HTTP/2 connection, implementations
36 * which target multiple connections should expect repetition of stream IDs.
37 *
38 * <p>Return true to request cancellation of a pushed stream.  Note that this
39 * does not guarantee future frames won't arrive on the stream ID.
40 */
41public interface PushObserver {
42  /**
43   * Describes the request that the server intends to push a response for.
44   *
45   * @param streamId server-initiated stream ID: an even number.
46   * @param requestHeaders minimally includes {@code :method}, {@code :scheme},
47   * {@code :authority}, and (@code :path}.
48   */
49  boolean onRequest(int streamId, List<Header> requestHeaders);
50
51  /**
52   * The response headers corresponding to a pushed request.  When {@code last}
53   * is true, there are no data frames to follow.
54   *
55   * @param streamId server-initiated stream ID: an even number.
56   * @param responseHeaders minimally includes {@code :status}.
57   * @param last when true, there is no response data.
58   */
59  boolean onHeaders(int streamId, List<Header> responseHeaders, boolean last);
60
61  /**
62   * A chunk of response data corresponding to a pushed request.  This data
63   * must either be read or skipped.
64   *
65   * @param streamId server-initiated stream ID: an even number.
66   * @param source location of data corresponding with this stream ID.
67   * @param byteCount number of bytes to read or skip from the source.
68   * @param last when true, there are no data frames to follow.
69   */
70  boolean onData(int streamId, BufferedSource source, int byteCount, boolean last)
71      throws IOException;
72
73  /** Indicates the reason why this stream was canceled. */
74  void onReset(int streamId, ErrorCode errorCode);
75
76  PushObserver CANCEL = new PushObserver() {
77
78    @Override public boolean onRequest(int streamId, List<Header> requestHeaders) {
79      return true;
80    }
81
82    @Override public boolean onHeaders(int streamId, List<Header> responseHeaders, boolean last) {
83      return true;
84    }
85
86    @Override public boolean onData(int streamId, BufferedSource source, int byteCount,
87        boolean last) throws IOException {
88      source.skip(byteCount);
89      return true;
90    }
91
92    @Override public void onReset(int streamId, ErrorCode errorCode) {
93    }
94  };
95}
96