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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  
16  package io.netty.handler.codec.http2;
17  
18  import io.netty.buffer.ByteBuf;
19  import io.netty.util.internal.UnstableApi;
20  
21  /**
22   * Decodes HPACK-encoded headers blocks into {@link Http2Headers}.
23   */
24  @UnstableApi
25  public interface Http2HeadersDecoder {
26      /**
27       * Configuration related elements for the {@link Http2HeadersDecoder} interface
28       */
29      interface Configuration {
30          /**
31           * Represents the value for
32           * <a href="https://tools.ietf.org/html/rfc7540#section-6.5.2">SETTINGS_HEADER_TABLE_SIZE</a>.
33           * This method should only be called by Netty (not users) as a result of a receiving a {@code SETTINGS} frame.
34           */
35          void maxHeaderTableSize(long max) throws Http2Exception;
36  
37          /**
38           * Represents the value for
39           * <a href="https://tools.ietf.org/html/rfc7540#section-6.5.2">SETTINGS_HEADER_TABLE_SIZE</a>. The initial value
40           * returned by this method must be {@link Http2CodecUtil#DEFAULT_HEADER_TABLE_SIZE}.
41           */
42          long maxHeaderTableSize();
43  
44          /**
45           * Configure the maximum allowed size in bytes of each set of headers.
46           * <p>
47           * This method should only be called by Netty (not users) as a result of a receiving a {@code SETTINGS} frame.
48           * @param max <a href="https://tools.ietf.org/html/rfc7540#section-6.5.2">SETTINGS_MAX_HEADER_LIST_SIZE</a>.
49           *      If this limit is exceeded the implementation should attempt to keep the HPACK header tables up to date
50           *      by processing data from the peer, but a {@code RST_STREAM} frame will be sent for the offending stream.
51           * @param goAwayMax Must be {@code >= max}. A {@code GO_AWAY} frame will be generated if this limit is exceeded
52           *                  for any particular stream.
53           * @throws Http2Exception if limits exceed the RFC's boundaries or {@code max > goAwayMax}.
54           */
55          void maxHeaderListSize(long max, long goAwayMax) throws Http2Exception;
56  
57          /**
58           * Represents the value for
59           * <a href="https://tools.ietf.org/html/rfc7540#section-6.5.2">SETTINGS_MAX_HEADER_LIST_SIZE</a>.
60           */
61          long maxHeaderListSize();
62  
63          /**
64           * Represents the upper bound in bytes for a set of headers before a {@code GO_AWAY} should be sent.
65           * This will be {@code <=}
66           * <a href="https://tools.ietf.org/html/rfc7540#section-6.5.2">SETTINGS_MAX_HEADER_LIST_SIZE</a>.
67           */
68          long maxHeaderListSizeGoAway();
69      }
70  
71      /**
72       * Decodes the given headers block and returns the headers.
73       */
74      Http2Headers decodeHeaders(int streamId, ByteBuf headerBlock) throws Http2Exception;
75  
76      /**
77       * Get the {@link Configuration} for this {@link Http2HeadersDecoder}
78       */
79      Configuration configuration();
80  }