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    1   /*
    2    *  Licensed to the Apache Software Foundation (ASF) under one
    3    *  or more contributor license agreements.  See the NOTICE file
    4    *  distributed with this work for additional information
    5    *  regarding copyright ownership.  The ASF licenses this file
    6    *  to you under the Apache License, Version 2.0 (the
    7    *  "License"); you may not use this file except in compliance
    8    *  with the License.  You may obtain a copy of the License at
    9    *
    10   *    http://www.apache.org/licenses/LICENSE-2.0
    11   *
    12   *  Unless required by applicable law or agreed to in writing,
    13   *  software distributed under the License is distributed on an
    14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    15   *  KIND, either express or implied.  See the License for the
    16   *  specific language governing permissions and limitations
    17   *  under the License.
    18   *
    19   */
    20  package org.apache.mina.filter.codec.statemachine;
    21
    22  import org.apache.mina.core.buffer.IoBuffer;
    23  import org.apache.mina.filter.codec.ProtocolDecoderException;
    24  import org.apache.mina.filter.codec.ProtocolDecoderOutput;
    25
    26  /**
    27   * {@link DecodingState} which decodes a single <code>CRLF</code>.
    28   * If it is found, the bytes are consumed and <code>true</code>
    29   * is provided as the product. Otherwise, read bytes are pushed back
    30   * to the stream, and <code>false</code> is provided as the
    31   * product.
    32   * Note that if we find a CR but do not find a following LF, we raise
    33   * an error.
    34   *
    35   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
    36   */
    37  public abstract class CrLfDecodingState implements DecodingState {
    38      /**
    39       * Carriage return character
    40       */
    41      private static final byte CR = 13;
    42
    43      /**
    44       * Line feed character
    45       */
    46      private static final byte LF = 10;
    47
    48      private boolean hasCR;
    49
    50      /**
    51       * {@inheritDoc}
    52       */
    53      public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out) throws Exception {
    54          boolean found = false;
    55          boolean finished = false;
    56          while (in.hasRemaining()) {
    57              byte b = in.get();
    58              if (!hasCR) {
    59                  if (b == CR) {
    60                      hasCR = true;
    61                  } else {
    62                      if (b == LF) {
    63                          found = true;
    64                      } else {
    65                          in.position(in.position() - 1);
    66                          found = false;
    67                      }
    68                      finished = true;
    69                      break;
    70                  }
    71              } else {
    72                  if (b == LF) {
    73                      found = true;
    74                      finished = true;
    75                      break;
    76                  }
    77
    78                  throw new ProtocolDecoderException("Expected LF after CR but was: " + (b & 0xff));
    79              }
    80          }
    81
    82          if (finished) {
    83              hasCR = false;
    84              return finishDecode(found, out);
    85          }
    86
    87          return this;
    88      }
    89
    90      /**
    91       * {@inheritDoc}
    92       */
    93      public DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception {
    94          return finishDecode(false, out);
    95      }
    96
    97      /**
    98       * Invoked when this state has found a <code>CRLF</code>.
    99       *
    100      * @param foundCRLF <code>true</code> if <code>CRLF</code> was found.
    101      * @param out the current {@link ProtocolDecoderOutput} used to write
    102      *        decoded messages.
    103      * @return the next state if a state transition was triggered (use
    104      *         <code>this</code> for loop transitions) or <code>null</code> if
    105      *         the state machine has reached its end.
    106      * @throws Exception if the read data violated protocol specification.
    107      */
    108     protected abstract DecodingState finishDecode(boolean foundCRLF, ProtocolDecoderOutput out) throws Exception;
    109 }