1 /* MessageDigestSpi.java --- The message digest service provider interface. 2 Copyright (C) 1999, 2005 Free Software Foundation, Inc. 3 4 This file is part of GNU Classpath. 5 6 GNU Classpath is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 GNU Classpath is distributed in the hope that it will be useful, but 12 WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GNU Classpath; see the file COPYING. If not, write to the 18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19 02110-1301 USA. 20 21 Linking this library statically or dynamically with other modules is 22 making a combined work based on this library. Thus, the terms and 23 conditions of the GNU General Public License cover the whole 24 combination. 25 26 As a special exception, the copyright holders of this library give you 27 permission to link this library with independent modules to produce an 28 executable, regardless of the license terms of these independent 29 modules, and to copy and distribute the resulting executable under 30 terms of your choice, provided that you also meet, for each linked 31 independent module, the terms and conditions of the license of that 32 module. An independent module is a module which is not derived from 33 or based on this library. If you modify this library, you may extend 34 this exception to your version of the library, but you are not 35 obligated to do so. If you do not wish to do so, delete this 36 exception statement from your version. */ 37 38 package java.security; 39 40 import java.nio.ByteBuffer; 41 42 /** 43 This is the Service Provider Interface (SPI) for MessageDigest 44 class in java.security. It provides the back end functionality 45 for the MessageDigest class so that it can compute message 46 hashes. The default hashes are SHA-1 and MD5. A message hash 47 takes data of arbitrary length and produces a unique number 48 representing it. 49 50 Cryptography service providers who want to implement their 51 own message digest hashes need only to subclass this class. 52 53 The implementation of a Cloneable interface is left to up to 54 the programmer of a subclass. 55 56 @version 0.0 57 58 @author Mark Benvenuto (ivymccough@worldnet.att.net) 59 */ 60 public abstract class MessageDigestSpi 61 { 62 /** 63 Default constructor of the MessageDigestSpi class 64 */ MessageDigestSpi()65 public MessageDigestSpi() 66 { 67 } 68 69 /** 70 Returns the length of the digest. It may be overridden by the 71 provider to return the length of the digest. Default is to 72 return 0. It is concrete for backwards compatibility with JDK1.1 73 message digest classes. 74 75 @return Length of Digest in Bytes 76 77 @since 1.2 78 */ engineGetDigestLength()79 protected int engineGetDigestLength() 80 { 81 return 0; 82 } 83 84 /** 85 Updates the digest with the specified byte. 86 87 @param input the byte to update digest with 88 */ engineUpdate(byte input)89 protected abstract void engineUpdate(byte input); 90 91 92 /** 93 Updates the digest with the specified bytes starting with the 94 offset and proceeding for the specified length. 95 96 @param input the byte array to update digest with 97 @param offset the offset of the byte to start with 98 @param len the number of the bytes to update with 99 */ engineUpdate(byte[]input, int offset, int len)100 protected abstract void engineUpdate(byte[]input, int offset, int len); 101 102 /** 103 * Updates this digest with the remaining bytes of a byte buffer. 104 * 105 * @param input The input buffer. 106 * @since 1.5 107 */ engineUpdate(ByteBuffer input)108 protected void engineUpdate (ByteBuffer input) 109 { 110 byte[] buf = new byte[1024]; 111 while (input.hasRemaining()) 112 { 113 int n = Math.min(input.remaining(), buf.length); 114 input.get (buf, 0, n); 115 engineUpdate (buf, 0, n); 116 } 117 } 118 119 /** 120 Computes the final digest of the stored bytes and returns 121 them. It performs any necessary padding. The message digest 122 should reset sensitive data after performing the digest. 123 124 @return An array of bytes containing the digest 125 */ engineDigest()126 protected abstract byte[] engineDigest(); 127 128 /** 129 Computes the final digest of the stored bytes and returns 130 them. It performs any necessary padding. The message digest 131 should reset sensitive data after performing the digest. This 132 method is left concrete for backwards compatibility with JDK1.1 133 message digest classes. 134 135 @param buf An array of bytes to store the digest 136 @param offset An offset to start storing the digest at 137 @param len The length of the buffer 138 @return Returns the length of the buffer 139 140 @since 1.2 141 */ engineDigest(byte[]buf, int offset, int len)142 protected int engineDigest(byte[]buf, int offset, int len) 143 throws DigestException 144 { 145 if (engineGetDigestLength() > len) 146 throw new DigestException("Buffer is too small."); 147 148 byte[] tmp = engineDigest(); 149 if (tmp.length > len) 150 throw new DigestException("Buffer is too small"); 151 152 System.arraycopy(tmp, 0, buf, offset, tmp.length); 153 return tmp.length; 154 } 155 156 /** 157 Resets the digest engine. Reinitializes internal variables 158 and clears sensitive data. 159 */ engineReset()160 protected abstract void engineReset(); 161 162 /** 163 Returns a clone of this class. 164 165 If cloning is not supported, then by default the class throws a 166 CloneNotSupportedException. The MessageDigestSpi provider 167 implementation has to overload this class in order to be 168 cloneable. 169 */ clone()170 public Object clone() throws CloneNotSupportedException 171 { 172 return super.clone(); 173 } 174 } 175