/*----------------------------------------------------------------------------*\
 *  CRC-32 version 2.0.0 by Craig Bruce, 2006-04-29.
 *
 *  This program generates the CRC-32 values for the files named in the
 *  command-line arguments.  These are the same CRC-32 values used by GZIP,
 *  PKZIP, and ZMODEM.  The Crc32_ComputeBuf() can also be detached and
 *  used independently.
 *
 *  THIS PROGRAM IS PUBLIC-DOMAIN SOFTWARE.
 *
 *  Based on the byte-oriented implementation "File Verification Using CRC"
 *  by Mark R. Nelson in Dr. Dobb's Journal, May 1992, pp. 64-67.
 *
 *  v1.0.0: original release.
 *  v1.0.1: fixed printf formats.
 *  v1.0.2: fixed something else.
 *  v1.0.3: replaced CRC constant table by generator function.
 *  v1.0.4: reformatted code, made ANSI C.  1994-12-05.
 *  v2.0.0: rewrote to use memory buffer & static table, 2006-04-29.
 *  v2.1.0: modified by Nico, 2013-04-20
 \*----------------------------------------------------------------------------*/

#include "crc32.h"

/*----------------------------------------------------------------------------*\
 *  NAME:
 *     Crc32_ComputeBuf() - computes the CRC-32 value of a memory buffer
 *  DESCRIPTION:
 *     Computes or accumulates the CRC-32 value for a memory buffer.
 *     The 'inCrc32' gives a previously accumulated CRC-32 value to allow
 *     a CRC to be generated for multiple sequential buffer-fuls of data.
 *     The 'inCrc32' for the first buffer must be zero.
 *  ARGUMENTS:
 *     inCrc32 - accumulated CRC-32 value, must be 0 on first call
 *     buf     - buffer to compute CRC-32 value for
 *     bufLen  - number of bytes in buffer
 *  RETURNS:
 *     crc32 - computed CRC-32 value
 *  ERRORS:
 *     (no errors are possible)
 \*----------------------------------------------------------------------------*/

unsigned long crc32_compute(unsigned long inCrc32, const void *buf, size_t bufLen) {
    static const unsigned long crcTable[256] = {
        0x00000000,0x77073096,0xEE0E612C,0x990951BA,0x076DC419,0x706AF48F,0xE963A535,
        0x9E6495A3,0x0EDB8832,0x79DCB8A4,0xE0D5E91E,0x97D2D988,0x09B64C2B,0x7EB17CBD,
        0xE7B82D07,0x90BF1D91,0x1DB71064,0x6AB020F2,0xF3B97148,0x84BE41DE,0x1ADAD47D,
        0x6DDDE4EB,0xF4D4B551,0x83D385C7,0x136C9856,0x646BA8C0,0xFD62F97A,0x8A65C9EC,
        0x14015C4F,0x63066CD9,0xFA0F3D63,0x8D080DF5,0x3B6E20C8,0x4C69105E,0xD56041E4,
        0xA2677172,0x3C03E4D1,0x4B04D447,0xD20D85FD,0xA50AB56B,0x35B5A8FA,0x42B2986C,
        0xDBBBC9D6,0xACBCF940,0x32D86CE3,0x45DF5C75,0xDCD60DCF,0xABD13D59,0x26D930AC,
        0x51DE003A,0xC8D75180,0xBFD06116,0x21B4F4B5,0x56B3C423,0xCFBA9599,0xB8BDA50F,
        0x2802B89E,0x5F058808,0xC60CD9B2,0xB10BE924,0x2F6F7C87,0x58684C11,0xC1611DAB,
        0xB6662D3D,0x76DC4190,0x01DB7106,0x98D220BC,0xEFD5102A,0x71B18589,0x06B6B51F,
        0x9FBFE4A5,0xE8B8D433,0x7807C9A2,0x0F00F934,0x9609A88E,0xE10E9818,0x7F6A0DBB,
        0x086D3D2D,0x91646C97,0xE6635C01,0x6B6B51F4,0x1C6C6162,0x856530D8,0xF262004E,
        0x6C0695ED,0x1B01A57B,0x8208F4C1,0xF50FC457,0x65B0D9C6,0x12B7E950,0x8BBEB8EA,
        0xFCB9887C,0x62DD1DDF,0x15DA2D49,0x8CD37CF3,0xFBD44C65,0x4DB26158,0x3AB551CE,
        0xA3BC0074,0xD4BB30E2,0x4ADFA541,0x3DD895D7,0xA4D1C46D,0xD3D6F4FB,0x4369E96A,
        0x346ED9FC,0xAD678846,0xDA60B8D0,0x44042D73,0x33031DE5,0xAA0A4C5F,0xDD0D7CC9,
        0x5005713C,0x270241AA,0xBE0B1010,0xC90C2086,0x5768B525,0x206F85B3,0xB966D409,
        0xCE61E49F,0x5EDEF90E,0x29D9C998,0xB0D09822,0xC7D7A8B4,0x59B33D17,0x2EB40D81,
        0xB7BD5C3B,0xC0BA6CAD,0xEDB88320,0x9ABFB3B6,0x03B6E20C,0x74B1D29A,0xEAD54739,
        0x9DD277AF,0x04DB2615,0x73DC1683,0xE3630B12,0x94643B84,0x0D6D6A3E,0x7A6A5AA8,
        0xE40ECF0B,0x9309FF9D,0x0A00AE27,0x7D079EB1,0xF00F9344,0x8708A3D2,0x1E01F268,
        0x6906C2FE,0xF762575D,0x806567CB,0x196C3671,0x6E6B06E7,0xFED41B76,0x89D32BE0,
        0x10DA7A5A,0x67DD4ACC,0xF9B9DF6F,0x8EBEEFF9,0x17B7BE43,0x60B08ED5,0xD6D6A3E8,
        0xA1D1937E,0x38D8C2C4,0x4FDFF252,0xD1BB67F1,0xA6BC5767,0x3FB506DD,0x48B2364B,
        0xD80D2BDA,0xAF0A1B4C,0x36034AF6,0x41047A60,0xDF60EFC3,0xA867DF55,0x316E8EEF,
        0x4669BE79,0xCB61B38C,0xBC66831A,0x256FD2A0,0x5268E236,0xCC0C7795,0xBB0B4703,
        0x220216B9,0x5505262F,0xC5BA3BBE,0xB2BD0B28,0x2BB45A92,0x5CB36A04,0xC2D7FFA7,
        0xB5D0CF31,0x2CD99E8B,0x5BDEAE1D,0x9B64C2B0,0xEC63F226,0x756AA39C,0x026D930A,
        0x9C0906A9,0xEB0E363F,0x72076785,0x05005713,0x95BF4A82,0xE2B87A14,0x7BB12BAE,
        0x0CB61B38,0x92D28E9B,0xE5D5BE0D,0x7CDCEFB7,0x0BDBDF21,0x86D3D2D4,0xF1D4E242,
        0x68DDB3F8,0x1FDA836E,0x81BE16CD,0xF6B9265B,0x6FB077E1,0x18B74777,0x88085AE6,
        0xFF0F6A70,0x66063BCA,0x11010B5C,0x8F659EFF,0xF862AE69,0x616BFFD3,0x166CCF45,
        0xA00AE278,0xD70DD2EE,0x4E048354,0x3903B3C2,0xA7672661,0xD06016F7,0x4969474D,
        0x3E6E77DB,0xAED16A4A,0xD9D65ADC,0x40DF0B66,0x37D83BF0,0xA9BCAE53,0xDEBB9EC5,
        0x47B2CF7F,0x30B5FFE9,0xBDBDF21C,0xCABAC28A,0x53B39330,0x24B4A3A6,0xBAD03605,
        0xCDD70693,0x54DE5729,0x23D967BF,0xB3667A2E,0xC4614AB8,0x5D681B02,0x2A6F2B94,
        0xB40BBE37,0xC30C8EA1,0x5A05DF1B,0x2D02EF8D
    };
    unsigned long crc32;
    unsigned char *byteBuf;
    size_t i;

    /** accumulate crc32 for buffer **/
    crc32 = inCrc32 ^ 0xFFFFFFFF;
    byteBuf = (unsigned char*) buf;
    for (i = 0; i < bufLen; i++) {
        crc32 = (crc32 >> 8) ^ crcTable[(crc32 ^ byteBuf[i]) & 0xFF];
    }
    return crc32 ^ 0xFFFFFFFF;
}
