CRC.cpp

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// -*- C++ -*-
/***************************************************************************
 *
 * The IPPL Framework
 *
 * This program was prepared by PSI.
 * All rights in the program are reserved by PSI.
 * Neither PSI nor the author(s)
 * makes any warranty, express or implied, or assumes any liability or
 * responsibility for the use of this software
 *
 * Visit www.amas.web.psi for more details
 *
 ***************************************************************************/

// -*- C++ -*-
/***************************************************************************
 *
 * The IPPL Framework
 *
 *
 * Visit http://people.web.psi.ch/adelmann/ for more details
 *
 ***************************************************************************/

/***************************************************************************
 *
 * Simple routine to calculate 32-bit CRC, assuming 32-bit integers.
 *
 ***************************************************************************/

// include files
#include "Message/CRC.h"

/* a table of values used in the calculation of the CRC for a buffer */
static CRCTYPE crctab[256] =
{
    0x00000000, 0x00007e00, 0x0000fc00, 0x00008200,
    0x000007ff, 0x000079ff, 0x0000fbff, 0x000085ff,
    0x00000fff, 0x000071ff, 0x0000f3ff, 0x00008dff,
    0x00000800, 0x00007600, 0x0000f400, 0x00008a00,
    0x00001fff, 0x000061ff, 0x0000e3ff, 0x00009dff,
    0x00001800, 0x00006600, 0x0000e400, 0x00009a00,
    0x00001000, 0x00006e00, 0x0000ec00, 0x00009200,
    0x000017ff, 0x000069ff, 0x0000ebff, 0x000095ff,
    0x00003fff, 0x000041ff, 0x0000c3ff, 0x0000bdff,
    0x00003800, 0x00004600, 0x0000c400, 0x0000ba00,
    0x00003000, 0x00004e00, 0x0000cc00, 0x0000b200,
    0x000037ff, 0x000049ff, 0x0000cbff, 0x0000b5ff,
    0x00002000, 0x00005e00, 0x0000dc00, 0x0000a200,
    0x000027ff, 0x000059ff, 0x0000dbff, 0x0000a5ff,
    0x00002fff, 0x000051ff, 0x0000d3ff, 0x0000adff,
    0x00002800, 0x00005600, 0x0000d400, 0x0000aa00,
    0x00007fff, 0x000001ff, 0x000083ff, 0x0000fdff,
    0x00007800, 0x00000600, 0x00008400, 0x0000fa00,
    0x00007000, 0x00000e00, 0x00008c00, 0x0000f200,
    0x000077ff, 0x000009ff, 0x00008bff, 0x0000f5ff,
    0x00006000, 0x00001e00, 0x00009c00, 0x0000e200,
    0x000067ff, 0x000019ff, 0x00009bff, 0x0000e5ff,
    0x00006fff, 0x000011ff, 0x000093ff, 0x0000edff,
    0x00006800, 0x00001600, 0x00009400, 0x0000ea00,
    0x00004000, 0x00003e00, 0x0000bc00, 0x0000c200,
    0x000047ff, 0x000039ff, 0x0000bbff, 0x0000c5ff,
    0x00004fff, 0x000031ff, 0x0000b3ff, 0x0000cdff,
    0x00004800, 0x00003600, 0x0000b400, 0x0000ca00,
    0x00005fff, 0x000021ff, 0x0000a3ff, 0x0000ddff,
    0x00005800, 0x00002600, 0x0000a400, 0x0000da00,
    0x00005000, 0x00002e00, 0x0000ac00, 0x0000d200,
    0x000057ff, 0x000029ff, 0x0000abff, 0x0000d5ff,
    0x0000ffff, 0x000081ff, 0x000003ff, 0x00007dff,
    0x0000f800, 0x00008600, 0x00000400, 0x00007a00,
    0x0000f000, 0x00008e00, 0x00000c00, 0x00007200,
    0x0000f7ff, 0x000089ff, 0x00000bff, 0x000075ff,
    0x0000e000, 0x00009e00, 0x00001c00, 0x00006200,
    0x0000e7ff, 0x000099ff, 0x00001bff, 0x000065ff,
    0x0000efff, 0x000091ff, 0x000013ff, 0x00006dff,
    0x0000e800, 0x00009600, 0x00001400, 0x00006a00,
    0x0000c000, 0x0000be00, 0x00003c00, 0x00004200,
    0x0000c7ff, 0x0000b9ff, 0x00003bff, 0x000045ff,
    0x0000cfff, 0x0000b1ff, 0x000033ff, 0x00004dff,
    0x0000c800, 0x0000b600, 0x00003400, 0x00004a00,
    0x0000dfff, 0x0000a1ff, 0x000023ff, 0x00005dff,
    0x0000d800, 0x0000a600, 0x00002400, 0x00005a00,
    0x0000d000, 0x0000ae00, 0x00002c00, 0x00005200,
    0x0000d7ff, 0x0000a9ff, 0x00002bff, 0x000055ff,
    0x00008000, 0x0000fe00, 0x00007c00, 0x00000200,
    0x000087ff, 0x0000f9ff, 0x00007bff, 0x000005ff,
    0x00008fff, 0x0000f1ff, 0x000073ff, 0x00000dff,
    0x00008800, 0x0000f600, 0x00007400, 0x00000a00,
    0x00009fff, 0x0000e1ff, 0x000063ff, 0x00001dff,
    0x00009800, 0x0000e600, 0x00006400, 0x00001a00,
    0x00009000, 0x0000ee00, 0x00006c00, 0x00001200,
    0x000097ff, 0x0000e9ff, 0x00006bff, 0x000015ff,
    0x0000bfff, 0x0000c1ff, 0x000043ff, 0x00003dff,
    0x0000b800, 0x0000c600, 0x00004400, 0x00003a00,
    0x0000b000, 0x0000ce00, 0x00004c00, 0x00003200,
    0x0000b7ff, 0x0000c9ff, 0x00004bff, 0x000035ff,
    0x0000a000, 0x0000de00, 0x00005c00, 0x00002200,
    0x0000a7ff, 0x0000d9ff, 0x00005bff, 0x000025ff,
    0x0000afff, 0x0000d1ff, 0x000053ff, 0x00002dff,
    0x0000a800, 0x0000d600, 0x00005400, 0x00002a00,
};


/* calculate the CRC for the given buffer of bytes, of length icnt */
CRCTYPE crc(void *icp, int icnt)
{
    int initcrc = -1;
    int cnt = icnt;
    CRCTYPE crc = (CRCTYPE)initcrc;
    unsigned char *cp = (unsigned char *)icp;
    while (cnt--)
        crc=((crc>>8)&0xffffff)^crctab[(crc&0xff)^*cp++];

    return(crc);
}