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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: /** 41: This is the Service Provider Interface (SPI) for MessageDigest 42: class in java.security. It provides the back end functionality 43: for the MessageDigest class so that it can compute message 44: hashes. The default hashes are SHA-1 and MD5. A message hash 45: takes data of arbitrary length and produces a unique number 46: representing it. 47: 48: Cryptography service providers who want to implement their 49: own message digest hashes need only to subclass this class. 50: 51: The implementation of a Cloneable interface is left to up to 52: the programmer of a subclass. 53: 54: @version 0.0 55: 56: @author Mark Benvenuto (ivymccough@worldnet.att.net) 57: */ 58: public abstract class MessageDigestSpi 59: { 60: /** 61: Default constructor of the MessageDigestSpi class 62: */ 63: public MessageDigestSpi() 64: { 65: } 66: 67: /** 68: Returns the length of the digest. It may be overridden by the 69: provider to return the length of the digest. Default is to 70: return 0. It is concrete for backwards compatibility with JDK1.1 71: message digest classes. 72: 73: @return Length of Digest in Bytes 74: 75: @since 1.2 76: */ 77: protected int engineGetDigestLength() 78: { 79: return 0; 80: } 81: 82: /** 83: Updates the digest with the specified byte. 84: 85: @param input the byte to update digest with 86: */ 87: protected abstract void engineUpdate(byte input); 88: 89: 90: /** 91: Updates the digest with the specified bytes starting with the 92: offset and proceeding for the specified length. 93: 94: @param input the byte array to update digest with 95: @param offset the offset of the byte to start with 96: @param len the number of the bytes to update with 97: */ 98: protected abstract void engineUpdate(byte[]input, int offset, int len); 99: 100: /** 101: Computes the final digest of the stored bytes and returns 102: them. It performs any necessary padding. The message digest 103: should reset sensitive data after performing the digest. 104: 105: @return An array of bytes containing the digest 106: */ 107: protected abstract byte[] engineDigest(); 108: 109: /** 110: Computes the final digest of the stored bytes and returns 111: them. It performs any necessary padding. The message digest 112: should reset sensitive data after performing the digest. This 113: method is left concrete for backwards compatibility with JDK1.1 114: message digest classes. 115: 116: @param buf An array of bytes to store the digest 117: @param offset An offset to start storing the digest at 118: @param len The length of the buffer 119: @return Returns the length of the buffer 120: 121: @since 1.2 122: */ 123: protected int engineDigest(byte[]buf, int offset, int len) 124: throws DigestException 125: { 126: if (engineGetDigestLength() > len) 127: throw new DigestException("Buffer is too small."); 128: 129: byte[] tmp = engineDigest(); 130: if (tmp.length > len) 131: throw new DigestException("Buffer is too small"); 132: 133: System.arraycopy(tmp, 0, buf, offset, tmp.length); 134: return tmp.length; 135: } 136: 137: /** 138: Resets the digest engine. Reinitializes internal variables 139: and clears sensitive data. 140: */ 141: protected abstract void engineReset(); 142: 143: /** 144: Returns a clone of this class. 145: 146: If cloning is not supported, then by default the class throws a 147: CloneNotSupportedException. The MessageDigestSpi provider 148: implementation has to overload this class in order to be 149: cloneable. 150: */ 151: public Object clone() throws CloneNotSupportedException 152: { 153: return super.clone(); 154: } 155: }
GNU Classpath (0.20) |