1 /* CheckedInputStream.java - Compute checksum of data being read 2 Copyright (C) 1999, 2000 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., 59 Temple Place, Suite 330, Boston, MA 19 02111-1307 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.util.zip; 39 40 import java.io.FilterInputStream; 41 import java.io.InputStream; 42 import java.io.IOException; 43 44 /* Written using on-line Java Platform 1.2 API Specification 45 * and JCL book. 46 * Believed complete and correct. 47 */ 48 49 /** 50 * InputStream that computes a checksum of the data being read using a 51 * supplied Checksum object. 52 * 53 * @see Checksum 54 * 55 * @author Tom Tromey 56 * @date May 17, 1999 57 */ 58 public class CheckedInputStream extends FilterInputStream 59 { 60 /** 61 * Creates a new CheckInputStream on top of the supplied OutputStream 62 * using the supplied Checksum. 63 */ CheckedInputStream(InputStream in, Checksum sum)64 public CheckedInputStream (InputStream in, Checksum sum) 65 { 66 super (in); 67 this.sum = sum; 68 } 69 70 /** 71 * Returns the Checksum object used. To get the data checksum computed so 72 * far call <code>getChecksum.getValue()</code>. 73 */ getChecksum()74 public Checksum getChecksum () 75 { 76 return sum; 77 } 78 79 /** 80 * Reads one byte, updates the checksum and returns the read byte 81 * (or -1 when the end of file was reached). 82 */ read()83 public int read () throws IOException 84 { 85 int x = in.read(); 86 if (x != -1) 87 sum.update(x); 88 return x; 89 } 90 91 /** 92 * Reads at most len bytes in the supplied buffer and updates the checksum 93 * with it. Returns the number of bytes actually read or -1 when the end 94 * of file was reached. 95 */ read(byte[] buf, int off, int len)96 public int read (byte[] buf, int off, int len) throws IOException 97 { 98 int r = in.read(buf, off, len); 99 if (r != -1) 100 sum.update(buf, off, r); 101 return r; 102 } 103 104 /** 105 * Skips n bytes by reading them in a temporary buffer and updating the 106 * the checksum with that buffer. Returns the actual number of bytes skiped 107 * which can be less then requested when the end of file is reached. 108 */ skip(long n)109 public long skip (long n) throws IOException 110 { 111 if (n == 0) 112 return 0; 113 114 int min = (int) Math.min(n, 1024); 115 byte[] buf = new byte[min]; 116 117 long s = 0; 118 while (n > 0) 119 { 120 int r = in.read(buf, 0, min); 121 if (r == -1) 122 break; 123 n -= r; 124 s += r; 125 min = (int) Math.min(n, 1024); 126 sum.update(buf, 0, r); 127 } 128 129 return s; 130 } 131 132 /** The checksum object. */ 133 private Checksum sum; 134 } 135