001: /*
002: * @(#)CheckedInputStream.java 1.23 06/10/10
003: *
004: * Copyright 1990-2006 Sun Microsystems, Inc. All Rights Reserved.
005: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
006: *
007: * This program is free software; you can redistribute it and/or
008: * modify it under the terms of the GNU General Public License version
009: * 2 only, as published by the Free Software Foundation.
010: *
011: * This program is distributed in the hope that it will be useful, but
012: * WITHOUT ANY WARRANTY; without even the implied warranty of
013: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014: * General Public License version 2 for more details (a copy is
015: * included at /legal/license.txt).
016: *
017: * You should have received a copy of the GNU General Public License
018: * version 2 along with this work; if not, write to the Free Software
019: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
020: * 02110-1301 USA
021: *
022: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
023: * Clara, CA 95054 or visit www.sun.com if you need additional
024: * information or have any questions.
025: *
026: */
027:
028: package java.util.zip;
029:
030: import java.io.FilterInputStream;
031: import java.io.InputStream;
032: import java.io.IOException;
033:
034: /**
035: * An input stream that also maintains a checksum of the data being read.
036: * The checksum can then be used to verify the integrity of the input data.
037: *
038: * @see Checksum
039: * @version 1.16, 02/02/00
040: * @author David Connelly
041: */
042: public class CheckedInputStream extends FilterInputStream {
043: private Checksum cksum;
044:
045: /**
046: * Creates an input stream using the specified Checksum.
047: * @param in the input stream
048: * @param cksum the Checksum
049: */
050: public CheckedInputStream(InputStream in, Checksum cksum) {
051: super (in);
052: this .cksum = cksum;
053: }
054:
055: /**
056: * Reads a byte. Will block if no input is available.
057: * @return the byte read, or -1 if the end of the stream is reached.
058: * @exception IOException if an I/O error has occurred
059: */
060: public int read() throws IOException {
061: int b = in.read();
062: if (b != -1) {
063: cksum.update(b);
064: }
065: return b;
066: }
067:
068: /**
069: * Reads into an array of bytes. Will block until some input
070: * is available.
071: * @param buf the buffer into which the data is read
072: * @param off the start offset of the data
073: * @param len the maximum number of bytes read
074: * @return the actual number of bytes read, or -1 if the end
075: * of the stream is reached.
076: * @exception IOException if an I/O error has occurred
077: */
078: public int read(byte[] buf, int off, int len) throws IOException {
079: len = in.read(buf, off, len);
080: if (len != -1) {
081: cksum.update(buf, off, len);
082: }
083: return len;
084: }
085:
086: /**
087: * Skips specified number of bytes of input.
088: * @param n the number of bytes to skip
089: * @return the actual number of bytes skipped
090: * @exception IOException if an I/O error has occurred
091: */
092: public long skip(long n) throws IOException {
093: byte[] buf = new byte[512];
094: long total = 0;
095: while (total < n) {
096: long len = n - total;
097: len = read(buf, 0, len < buf.length ? (int) len
098: : buf.length);
099: if (len == -1) {
100: return total;
101: }
102: total += len;
103: }
104: return total;
105: }
106:
107: /**
108: * Returns the Checksum for this input stream.
109: * @return the Checksum value
110: */
111: public Checksum getChecksum() {
112: return cksum;
113: }
114: }
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