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1   /*
2    * Copyright 2014 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
5    * "License"); you may not use this file except in compliance with the License. You may obtain a
6    * 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 distributed under the License
11   * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
12   * or implied. See the License for the specific language governing permissions and limitations under
13   * the License.
14   */
15  package io.netty.handler.codec.http2;
16  
17  import io.netty.buffer.ByteBuf;
18  import io.netty.util.internal.UnstableApi;
19  
20  /**
21   * A {@link Http2FlowController} for controlling the inbound flow of {@code DATA} frames from the remote endpoint.
22   */
23  @UnstableApi
24  public interface Http2LocalFlowController extends Http2FlowController {
25      /**
26       * Sets the writer to be use for sending {@code WINDOW_UPDATE} frames. This must be called before any flow
27       * controlled data is received.
28       *
29       * @param frameWriter the HTTP/2 frame writer.
30       */
31      Http2LocalFlowController frameWriter(Http2FrameWriter frameWriter);
32  
33      /**
34       * Receives an inbound {@code DATA} frame from the remote endpoint and applies flow control policies to it for both
35       * the {@code stream} as well as the connection. If any flow control policies have been violated, an exception is
36       * raised immediately, otherwise the frame is considered to have "passed" flow control.
37       * <p/>
38       * If {@code stream} is {@code null} or closed, flow control should only be applied to the connection window and the
39       * bytes are immediately consumed.
40       *
41       * @param stream the subject stream for the received frame. The connection stream object must not be used. If {@code
42       * stream} is {@code null} or closed, flow control should only be applied to the connection window and the bytes are
43       * immediately consumed.
44       * @param data payload buffer for the frame.
45       * @param padding additional bytes that should be added to obscure the true content size. Must be between 0 and
46       *                256 (inclusive).
47       * @param endOfStream Indicates whether this is the last frame to be sent from the remote endpoint for this stream.
48       * @throws Http2Exception if any flow control errors are encountered.
49       */
50      void receiveFlowControlledFrame(Http2Stream stream, ByteBuf data, int padding,
51                                      boolean endOfStream) throws Http2Exception;
52  
53      /**
54       * Indicates that the application has consumed a number of bytes for the given stream and is therefore ready to
55       * receive more data from the remote endpoint. The application must consume any bytes that it receives or the flow
56       * control window will collapse. Consuming bytes enables the flow controller to send {@code WINDOW_UPDATE} to
57       * restore a portion of the flow control window for the stream.
58       * <p/>
59       * If {@code stream} is {@code null} or closed (i.e. {@link Http2Stream#state()} method returns {@link
60       * Http2Stream.State#CLOSED}), calling this method has no effect.
61       *
62       * @param stream the stream for which window space should be freed. The connection stream object must not be used.
63       * If {@code stream} is {@code null} or closed (i.e. {@link Http2Stream#state()} method returns {@link
64       * Http2Stream.State#CLOSED}), calling this method has no effect.
65       * @param numBytes the number of bytes to be returned to the flow control window.
66       * @return true if a {@code WINDOW_UPDATE} was sent, false otherwise.
67       * @throws Http2Exception if the number of bytes returned exceeds the {@link #unconsumedBytes(Http2Stream)} for the
68       * stream.
69       */
70      boolean consumeBytes(Http2Stream stream, int numBytes) throws Http2Exception;
71  
72      /**
73       * The number of bytes for the given stream that have been received but not yet consumed by the
74       * application.
75       *
76       * @param stream the stream for which window space should be freed.
77       * @return the number of unconsumed bytes for the stream.
78       */
79      int unconsumedBytes(Http2Stream stream);
80  
81      /**
82       * Get the initial flow control window size for the given stream. This quantity is measured in number of bytes. Note
83       * the unavailable window portion can be calculated by {@link #initialWindowSize()} - {@link
84       * #windowSize(Http2Stream)}.
85       */
86      int initialWindowSize(Http2Stream stream);
87  }