MessageLengthDecoder


1   /*_############################################################################
2     _## 
3     _##  SNMP4J - MessageLengthDecoder.java  
4     _## 
5     _##  Copyright 2003-2007  Frank Fock and Jochen Katz (SNMP4J.org)
6     _##  
7     _##  Licensed under the Apache License, Version 2.0 (the "License");
8     _##  you may not use this file except in compliance with the License.
9     _##  You may obtain a copy of the License at
10    _##  
11    _##      http://www.apache.org/licenses/LICENSE-2.0
12    _##  
13    _##  Unless required by applicable law or agreed to in writing, software
14    _##  distributed under the License is distributed on an "AS IS" BASIS,
15    _##  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16    _##  See the License for the specific language governing permissions and
17    _##  limitations under the License.
18    _##  
19    _##########################################################################*/
20  
21  
22  package org.snmp4j.transport;
23  
24  import java.nio.ByteBuffer  ;
25  import java.io.IOException  ;
26  
27  /**
28   * The <code>MessageLengthDecoder</code> needs to be implemented for connection
29   * oriented transport mappings, because those transport mappings have no message
30   * boundaries. To determine the message length, the message header is decoded
31   * in a protocol specific way.
32   *
33   * @author Frank Fock
34   * @version 1.7
35   * @since 1.7
36   */
37  public interface MessageLengthDecoder {
38  
39    /**
40     * Returns the minimum length of the header to be decoded. Typically this
41     * is a constant value.
42     * @return
43     *    the minimum length in bytes.
44     */
45    int getMinHeaderLength();
46  
47    /**
48     * Returns the total message length to read (including header) and
49     * the actual header length.
50     * @param buf
51     *    a ByteBuffer with a minimum of {@link #getMinHeaderLength()}.
52     * @return
53     *    the total message length in bytes and the actual header length in bytes.
54     * @throws IOException
55     *    if the header cannot be decoded.
56     */
57    MessageLength getMessageLength(ByteBuffer   buf) throws IOException  ;
58  
59  }
60
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