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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: 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: */ 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: */ 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: */ 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: */ 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: */ 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: */ 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: */ 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: */ 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: */ 170: public Object clone() throws CloneNotSupportedException 171: { 172: return super.clone(); 173: } 174: }