diff options
Diffstat (limited to 'libjava/java/util/zip/CRC32.java')
| -rw-r--r-- | libjava/java/util/zip/CRC32.java | 69 |
1 files changed, 57 insertions, 12 deletions
diff --git a/libjava/java/util/zip/CRC32.java b/libjava/java/util/zip/CRC32.java index 1abbcad..c6d9ed4 100644 --- a/libjava/java/util/zip/CRC32.java +++ b/libjava/java/util/zip/CRC32.java @@ -1,17 +1,30 @@ -/* Copyright (C) 1999 Free Software Foundation +/* CRC32.java - Computes CRC32 data checksum of a data stream + Copyright (C) 1999, 2000 Free Software Foundation, Inc. - This file is part of libgcj. +This file is part of GNU Classpath. -This software is copyrighted work licensed under the terms of the -Libgcj License. Please consult the file "LIBGCJ_LICENSE" for -details. */ +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. -package java.util.zip; +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA +02111-1307 USA. -/** - * @author Per Bothner - * @date April 1, 1999. - */ +As a special exception, if you link this library with other files to +produce an executable, this library does not by itself cause the +resulting executable to be covered by the GNU General Public License. +This exception does not however invalidate any other reasons why the +executable file might be covered by the GNU General Public License. */ + +package java.util.zip; /* * Written using on-line Java Platform 1.2 API Specification, as well @@ -20,14 +33,29 @@ package java.util.zip; * Status: Believed complete and correct. */ +/** + * Computes CRC32 data checksum of a data stream. + * The actual CRC32 algorithm is described in RFC 1952 + * (GZIP file format specification version 4.3). + * Can be used to get the CRC32 over a stream if used with checked input/output + * streams. + * + * @see InflaterInputStream + * @see InflaterOutputStream + * + * @author Per Bothner + * @date April 1, 1999. + */ public class CRC32 implements Checksum { + /** The crc data checksum so far. */ private int crc = 0; + /** The fast CRC table. Computed once when the CRC32 class is loaded. */ private static int[] crc_table = make_crc_table(); - /* Make the table for a fast CRC. */ - static int[] make_crc_table () + /** Make the table for a fast CRC. */ + private static int[] make_crc_table () { int[] crc_table = new int[256]; for (int n = 0; n < 256; n++) @@ -45,11 +73,17 @@ public class CRC32 implements Checksum return crc_table; } + /** + * Returns the CRC32 data checksum computed so far. + */ public long getValue () { return (long) crc & 0xffffffffL; } + /** + * Resets the CRC32 data checksum as if no update was ever called. + */ public void reset () { crc = 0; } public void update (int bval) @@ -59,6 +93,13 @@ public class CRC32 implements Checksum crc = ~c; } + /** + * Adds the byte array to the data checksum. + * + * @param buf the buffer which contains the data + * @param off the offset in the buffer where the data starts + * @param len the length of the data + */ public void update (byte[] buf, int off, int len) { int c = ~crc; @@ -66,5 +107,9 @@ public class CRC32 implements Checksum c = crc_table[(c ^ buf[off++]) & 0xff] ^ (c >>> 8); crc = ~c; } + + /** + * Adds the complete byte array to the data checksum. + */ public void update (byte[] buf) { update(buf, 0, buf.length); } } |