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Diffstat (limited to 'openjdk/java/util/zip/Adler32.java')
| -rw-r--r-- | openjdk/java/util/zip/Adler32.java | 205 |
1 files changed, 0 insertions, 205 deletions
diff --git a/openjdk/java/util/zip/Adler32.java b/openjdk/java/util/zip/Adler32.java deleted file mode 100644 index fc1536aa..00000000 --- a/openjdk/java/util/zip/Adler32.java +++ /dev/null @@ -1,205 +0,0 @@ -/* Adler32.java - Computes Adler32 data checksum of a data stream - Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc. - -This file is part of GNU Classpath. - -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. - -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., 51 Franklin Street, Fifth Floor, Boston, MA -02110-1301 USA. - -Linking this library statically or dynamically with other modules is -making a combined work based on this library. Thus, the terms and -conditions of the GNU General Public License cover the whole -combination. - -As a special exception, the copyright holders of this library give you -permission to link this library with independent modules to produce an -executable, regardless of the license terms of these independent -modules, and to copy and distribute the resulting executable under -terms of your choice, provided that you also meet, for each linked -independent module, the terms and conditions of the license of that -module. An independent module is a module which is not derived from -or based on this library. If you modify this library, you may extend -this exception to your version of the library, but you are not -obligated to do so. If you do not wish to do so, delete this -exception statement from your version. */ - -package java.util.zip; - -/* - * Written using on-line Java Platform 1.2 API Specification, as well - * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998). - * The actual Adler32 algorithm is taken from RFC 1950. - * Status: Believed complete and correct. - */ - -/** - * Computes Adler32 checksum for a stream of data. An Adler32 - * checksum is not as reliable as a CRC32 checksum, but a lot faster to - * compute. - *<p> - * The specification for Adler32 may be found in RFC 1950. - * (ZLIB Compressed Data Format Specification version 3.3) - *<p> - *<p> - * From that document: - *<p> - * "ADLER32 (Adler-32 checksum) - * This contains a checksum value of the uncompressed data - * (excluding any dictionary data) computed according to Adler-32 - * algorithm. This algorithm is a 32-bit extension and improvement - * of the Fletcher algorithm, used in the ITU-T X.224 / ISO 8073 - * standard. - *<p> - * Adler-32 is composed of two sums accumulated per byte: s1 is - * the sum of all bytes, s2 is the sum of all s1 values. Both sums - * are done modulo 65521. s1 is initialized to 1, s2 to zero. The - * Adler-32 checksum is stored as s2*65536 + s1 in most- - * significant-byte first (network) order." - *<p> - * "8.2. The Adler-32 algorithm - *<p> - * The Adler-32 algorithm is much faster than the CRC32 algorithm yet - * still provides an extremely low probability of undetected errors. - *<p> - * The modulo on unsigned long accumulators can be delayed for 5552 - * bytes, so the modulo operation time is negligible. If the bytes - * are a, b, c, the second sum is 3a + 2b + c + 3, and so is position - * and order sensitive, unlike the first sum, which is just a - * checksum. That 65521 is prime is important to avoid a possible - * large class of two-byte errors that leave the check unchanged. - * (The Fletcher checksum uses 255, which is not prime and which also - * makes the Fletcher check insensitive to single byte changes 0 <-> - * 255.) - *<p> - * The sum s1 is initialized to 1 instead of zero to make the length - * of the sequence part of s2, so that the length does not have to be - * checked separately. (Any sequence of zeroes has a Fletcher - * checksum of zero.)" - * - * @author John Leuner, Per Bothner - * @since JDK 1.1 - * - * @see InflaterInputStream - * @see DeflaterOutputStream - */ -public class Adler32 implements Checksum -{ - - /** largest prime smaller than 65536 */ - private static final int BASE = 65521; - - private int adler; //we do all in int. - - //Note that java doesn't have unsigned integers, - //so we have to be careful with what arithmetic - //we do. We return the checksum as a long to - //avoid sign confusion. - - /** - * Creates a new instance of the <code>Adler32</code> class. - * The checksum starts off with a value of 1. - */ - public Adler32 () - { - reset(); - } - - /** - * Resets the Adler32 checksum to the initial value. - */ - public void reset () - { - adler = 1; //Initialize to 1 - } - - /** - * Updates the checksum with the byte b. - * - * @param bval the data value to add. The high byte of the int is ignored. - */ - public void update (int bval) - { - //We could make a length 1 byte array and call update again, but I - //would rather not have that overhead - int s1 = adler & 0xffff; - int s2 = adler >>> 16; - - s1 = (s1 + (bval & 0xFF)) % BASE; - s2 = (s1 + s2) % BASE; - - adler = (s2 << 16) + s1; - } - - /** - * Updates the checksum with the bytes taken from the array. - * - * @param buffer an array of bytes - */ - public void update (byte[] buffer) - { - update(buffer, 0, buffer.length); - } - - /** - * Updates the checksum with the bytes taken from the array. - * - * @param buf an array of bytes - * @param off the start of the data used for this update - * @param len the number of bytes to use for this update - */ - public void update (byte[] buf, int off, int len) - { - //(By Per Bothner) - int s1 = adler & 0xffff; - int s2 = adler >>> 16; - - while (len > 0) - { - // We can defer the modulo operation: - // s1 maximally grows from 65521 to 65521 + 255 * 3800 - // s2 maximally grows by 3800 * median(s1) = 2090079800 < 2^31 - int n = 3800; - if (n > len) - n = len; - len -= n; - while (--n >= 0) - { - s1 = s1 + (buf[off++] & 0xFF); - s2 = s2 + s1; - } - s1 %= BASE; - s2 %= BASE; - } - - /*Old implementation, borrowed from somewhere: - int n; - - while (len-- > 0) { - - s1 = (s1 + (bs[offset++] & 0xff)) % BASE; - s2 = (s2 + s1) % BASE; - }*/ - - adler = (s2 << 16) | s1; - } - - /** - * Returns the Adler32 data checksum computed so far. - */ - public long getValue() - { - return (long) adler & 0xffffffffL; - } -} |