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1   /*
2    * Copyright 2016 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.redis;
17  
18  import io.netty.channel.ChannelHandlerContext;
19  import io.netty.handler.codec.CodecException;
20  import io.netty.handler.codec.MessageToMessageDecoder;
21  import io.netty.util.ReferenceCountUtil;
22  import io.netty.util.internal.UnstableApi;
23  
24  import java.util.ArrayDeque;
25  import java.util.ArrayList;
26  import java.util.Deque;
27  import java.util.List;
28  
29  /**
30   * Aggregates {@link RedisMessage} parts into {@link ArrayRedisMessage}. This decoder
31   * should be used together with {@link RedisDecoder}.
32   */
33  @UnstableApi
34  public final class RedisArrayAggregator extends MessageToMessageDecoder<RedisMessage> {
35  
36      private final Deque<AggregateState> depths = new ArrayDeque<AggregateState>(4);
37  
38      @Override
39      protected void decode(ChannelHandlerContext ctx, RedisMessage msg, List<Object> out) throws Exception {
40          if (msg instanceof ArrayHeaderRedisMessage) {
41              msg = decodeRedisArrayHeader((ArrayHeaderRedisMessage) msg);
42              if (msg == null) {
43                  return;
44              }
45          } else {
46              ReferenceCountUtil.retain(msg);
47          }
48  
49          while (!depths.isEmpty()) {
50              AggregateState current = depths.peek();
51              current.children.add(msg);
52  
53              // if current aggregation completed, go to parent aggregation.
54              if (current.children.size() == current.length) {
55                  msg = new ArrayRedisMessage(current.children);
56                  depths.pop();
57              } else {
58                  // not aggregated yet. try next time.
59                  return;
60              }
61          }
62  
63          out.add(msg);
64      }
65  
66      private RedisMessage decodeRedisArrayHeader(ArrayHeaderRedisMessage header) {
67          if (header.isNull()) {
68              return ArrayRedisMessage.NULL_INSTANCE;
69          } else if (header.length() == 0L) {
70              return ArrayRedisMessage.EMPTY_INSTANCE;
71          } else if (header.length() > 0L) {
72              // Currently, this codec doesn't support `long` length for arrays because Java's List.size() is int.
73              if (header.length() > Integer.MAX_VALUE) {
74                  throw new CodecException("this codec doesn't support longer length than " + Integer.MAX_VALUE);
75              }
76  
77              // start aggregating array
78              depths.push(new AggregateState((int) header.length()));
79              return null;
80          } else {
81              throw new CodecException("bad length: " + header.length());
82          }
83      }
84  
85      private static final class AggregateState {
86          private final int length;
87          private final List<RedisMessage> children;
88          AggregateState(int length) {
89              this.length = length;
90              this.children = new ArrayList<RedisMessage>(length);
91          }
92      }
93  }