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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,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. 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, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.handler.codec.smtp;
17  
18  import io.netty.buffer.ByteBuf;
19  import io.netty.channel.ChannelHandlerContext;
20  import io.netty.handler.codec.DecoderException;
21  import io.netty.handler.codec.LineBasedFrameDecoder;
22  import io.netty.util.CharsetUtil;
23  import io.netty.util.internal.UnstableApi;
24  
25  import java.util.ArrayList;
26  import java.util.Collections;
27  import java.util.List;
28  
29  /**
30   * Decoder for SMTP responses.
31   */
32  @UnstableApi
33  public final class SmtpResponseDecoder extends LineBasedFrameDecoder {
34  
35      private List<CharSequence> details;
36  
37      /**
38       * Creates a new instance that enforces the given {@code maxLineLength}.
39       */
40      public SmtpResponseDecoder(int maxLineLength) {
41          super(maxLineLength);
42      }
43  
44      @Override
45      protected SmtpResponse decode(ChannelHandlerContext ctx, ByteBuf buffer) throws Exception {
46          ByteBuf frame = (ByteBuf) super.decode(ctx, buffer);
47          if (frame == null) {
48              // No full line received yet.
49              return null;
50          }
51          try {
52              final int readable = frame.readableBytes();
53              final int readerIndex = frame.readerIndex();
54              if (readable < 3) {
55                  throw newDecoderException(buffer, readerIndex, readable);
56              }
57              final int code = parseCode(frame);
58              final int separator = frame.readByte();
59              final CharSequence detail = frame.isReadable() ? frame.toString(CharsetUtil.US_ASCII) : null;
60  
61              List<CharSequence> details = this.details;
62  
63              switch (separator) {
64              case ' ':
65                  // Marks the end of a response.
66                  this.details = null;
67                  if (details != null) {
68                      if (detail != null) {
69                          details.add(detail);
70                      }
71                  } else {
72                      if (detail == null) {
73                          details = Collections.emptyList();
74                      } else {
75                          details = Collections.singletonList(detail);
76                      }
77                  }
78                  return new DefaultSmtpResponse(code, details);
79              case '-':
80                  // Multi-line response.
81                  if (detail != null) {
82                      if (details == null) {
83                          // Using initial capacity as it is very unlikely that we will receive a multi-line response
84                          // with more then 3 lines.
85                          this.details = details = new ArrayList<CharSequence>(4);
86                      }
87                      details.add(detail);
88                  }
89                  break;
90              default:
91                  throw newDecoderException(buffer, readerIndex, readable);
92              }
93          } finally {
94              frame.release();
95          }
96          return null;
97      }
98  
99      private static DecoderException newDecoderException(ByteBuf buffer, int readerIndex, int readable) {
100         return new DecoderException(
101                 "Received invalid line: '" + buffer.toString(readerIndex, readable, CharsetUtil.US_ASCII) + '\'');
102     }
103 
104     /**
105      * Parses the io.netty.handler.codec.smtp code without any allocation, which is three digits.
106      */
107     private static int parseCode(ByteBuf buffer) {
108         final int first = parseNumber(buffer.readByte()) * 100;
109         final int second = parseNumber(buffer.readByte()) * 10;
110         final int third = parseNumber(buffer.readByte());
111         return first + second + third;
112     }
113 
114     private static int parseNumber(byte b) {
115         return Character.digit((char) b, 10);
116     }
117 }