71 lines
1.4 KiB
Java
71 lines
1.4 KiB
Java
/* Copyright (C) 1999 Cygnus Solutions
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package java.util.zip;
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/**
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* @author Per Bothner
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* @date April 1, 1999.
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*/
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/*
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* Written using on-line Java Platform 1.2 API Specification, as well
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* as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
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* The actual CRC32 algorithm is taken from RFC 1952.
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* Status: Believed complete and correct.
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*/
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public class CRC32 implements Checksum
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{
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int crc = 0;
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static int[] crc_table = make_crc_table();
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/* Make the table for a fast CRC. */
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static int[] make_crc_table ()
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{
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int[] crc_table = new int[256];
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for (int n = 0; n < 256; n++)
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{
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int c = n;
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for (int k = 8; --k >= 0; )
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{
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if ((c & 1) != 0)
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c = 0xedb88320 ^ (c >>> 1);
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else
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c = c >>> 1;
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}
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crc_table[n] = c;
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}
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return crc_table;
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}
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public long getValue ()
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{
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return (long) crc & 0xffffffffL;
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}
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public void reset () { crc = 0; }
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public void update (int bval)
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{
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int c = ~crc;
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c = crc_table[(c ^ bval) & 0xff] ^ (c >>> 8);
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crc = ~c;
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}
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public void update (byte[] buf, int off, int len)
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{
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int c = ~crc;
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while (--len >= 0)
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c = crc_table[(c ^ buf[off++]) & 0xff] ^ (c >>> 8);
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crc = ~c;
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}
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public void update (byte[] buf) { update(buf, 0, buf.length); }
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}
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