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@@ -0,0 +1,231 @@
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+unit crc;
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+
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+{
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+ crc32.c -- compute the CRC-32 of a data stream
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+ Copyright (C) 1995-1998 Mark Adler
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+
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+ Pascal tranlastion
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+ Copyright (C) 1998 by Jacques Nomssi Nzali
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+ For conditions of distribution and use, see copyright notice in readme.txt
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+}
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+
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+interface
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+
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+function crc32(crc : cardinal; buf : Pbyte; len : cardinal) : cardinal;
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+
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+{ Update a running crc with the bytes buf[0..len-1] and return the updated
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+ crc. If buf is NULL, this function returns the required initial value
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+ for the crc. Pre- and post-conditioning (one's complement) is performed
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+ within this function so it shouldn't be done by the application.
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+ Usage example:
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+
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+ var
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+ crc : cardinal;
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+ begin
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+ crc := crc32(0, nil, 0);
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+
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+ while (read_buffer(buffer, length) <> EOF) do
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+ crc := crc32(crc, buffer, length);
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+
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+ if (crc <> original_crc) then error();
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+ end;
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+
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+}
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+
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+function get_crc_table : Pcardinal; { can be used by asm versions of crc32() }
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+
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+
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+implementation
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+
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+{$IFDEF DYNAMIC_CRC_TABLE}
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+
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+{local}
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+const
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+ crc_table_empty : boolean = TRUE;
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+{local}
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+var
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+ crc_table : array[0..256-1] of uLongf;
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+
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+
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+{
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+ Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
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+ x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
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+
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+ Polynomials over GF(2) are represented in binary, one bit per coefficient,
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+ with the lowest powers in the most significant bit. Then adding polynomials
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+ is just exclusive-or, and multiplying a polynomial by x is a right shift by
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+ one. If we call the above polynomial p, and represent a byte as the
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+ polynomial q, also with the lowest power in the most significant bit (so the
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+ byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
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+ where a mod b means the remainder after dividing a by b.
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+
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+ This calculation is done using the shift-register method of multiplying and
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+ taking the remainder. The register is initialized to zero, and for each
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+ incoming bit, x^32 is added mod p to the register if the bit is a one (where
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+ x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
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+ x (which is shifting right by one and adding x^32 mod p if the bit shifted
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+ out is a one). We start with the highest power (least significant bit) of
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+ q and repeat for all eight bits of q.
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+
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+ The table is simply the CRC of all possible eight bit values. This is all
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+ the information needed to generate CRC's on data a byte at a time for all
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+ combinations of CRC register values and incoming bytes.
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+}
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+{local}
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+procedure make_crc_table;
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+var
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+ c : cardinal;
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+ n,k : integer;
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+ poly : cardinal; { polynomial exclusive-or pattern }
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+
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+const
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+ { terms of polynomial defining this crc (except x^32): }
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+ p: array [0..13] of Byte = (0,1,2,4,5,7,8,10,11,12,16,22,23,26);
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+
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+begin
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+ { make exclusive-or pattern from polynomial ($EDB88320) }
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+ poly := longint(0);
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+ for n := 0 to (sizeof(p) div sizeof(Byte))-1 do
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+ poly := poly or (longint(1) shl (31 - p[n]));
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+
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+ for n := 0 to 255 do
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+ begin
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+ c := cardinal(n);
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+ for k := 0 to 7 do
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+ begin
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+ if (c and 1) <> 0 then
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+ c := poly xor (c shr 1)
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+ else
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+ c := (c shr 1);
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+ end;
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+ crc_table[n] := c;
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+ end;
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+ crc_table_empty := FALSE;
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+end;
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+
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+{$ELSE}
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+
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+{ ========================================================================
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+ Table of CRC-32's of all single-byte values (made by make_crc_table) }
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+
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+{local}
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+const
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+ crc_table : array[0..256-1] of cardinal = (
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+ $00000000, $77073096, $ee0e612c, $990951ba, $076dc419,
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+ $706af48f, $e963a535, $9e6495a3, $0edb8832, $79dcb8a4,
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+ $e0d5e91e, $97d2d988, $09b64c2b, $7eb17cbd, $e7b82d07,
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+ $90bf1d91, $1db71064, $6ab020f2, $f3b97148, $84be41de,
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+ $1adad47d, $6ddde4eb, $f4d4b551, $83d385c7, $136c9856,
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+ $646ba8c0, $fd62f97a, $8a65c9ec, $14015c4f, $63066cd9,
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+ $fa0f3d63, $8d080df5, $3b6e20c8, $4c69105e, $d56041e4,
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+ $a2677172, $3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b,
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+ $35b5a8fa, $42b2986c, $dbbbc9d6, $acbcf940, $32d86ce3,
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+ $45df5c75, $dcd60dcf, $abd13d59, $26d930ac, $51de003a,
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+ $c8d75180, $bfd06116, $21b4f4b5, $56b3c423, $cfba9599,
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+ $b8bda50f, $2802b89e, $5f058808, $c60cd9b2, $b10be924,
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+ $2f6f7c87, $58684c11, $c1611dab, $b6662d3d, $76dc4190,
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+ $01db7106, $98d220bc, $efd5102a, $71b18589, $06b6b51f,
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+ $9fbfe4a5, $e8b8d433, $7807c9a2, $0f00f934, $9609a88e,
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+ $e10e9818, $7f6a0dbb, $086d3d2d, $91646c97, $e6635c01,
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+ $6b6b51f4, $1c6c6162, $856530d8, $f262004e, $6c0695ed,
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+ $1b01a57b, $8208f4c1, $f50fc457, $65b0d9c6, $12b7e950,
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+ $8bbeb8ea, $fcb9887c, $62dd1ddf, $15da2d49, $8cd37cf3,
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+ $fbd44c65, $4db26158, $3ab551ce, $a3bc0074, $d4bb30e2,
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+ $4adfa541, $3dd895d7, $a4d1c46d, $d3d6f4fb, $4369e96a,
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+ $346ed9fc, $ad678846, $da60b8d0, $44042d73, $33031de5,
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+ $aa0a4c5f, $dd0d7cc9, $5005713c, $270241aa, $be0b1010,
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+ $c90c2086, $5768b525, $206f85b3, $b966d409, $ce61e49f,
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+ $5edef90e, $29d9c998, $b0d09822, $c7d7a8b4, $59b33d17,
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+ $2eb40d81, $b7bd5c3b, $c0ba6cad, $edb88320, $9abfb3b6,
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+ $03b6e20c, $74b1d29a, $ead54739, $9dd277af, $04db2615,
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+ $73dc1683, $e3630b12, $94643b84, $0d6d6a3e, $7a6a5aa8,
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+ $e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1, $f00f9344,
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+ $8708a3d2, $1e01f268, $6906c2fe, $f762575d, $806567cb,
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+ $196c3671, $6e6b06e7, $fed41b76, $89d32be0, $10da7a5a,
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+ $67dd4acc, $f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5,
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+ $d6d6a3e8, $a1d1937e, $38d8c2c4, $4fdff252, $d1bb67f1,
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+ $a6bc5767, $3fb506dd, $48b2364b, $d80d2bda, $af0a1b4c,
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+ $36034af6, $41047a60, $df60efc3, $a867df55, $316e8eef,
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+ $4669be79, $cb61b38c, $bc66831a, $256fd2a0, $5268e236,
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+ $cc0c7795, $bb0b4703, $220216b9, $5505262f, $c5ba3bbe,
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+ $b2bd0b28, $2bb45a92, $5cb36a04, $c2d7ffa7, $b5d0cf31,
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+ $2cd99e8b, $5bdeae1d, $9b64c2b0, $ec63f226, $756aa39c,
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+ $026d930a, $9c0906a9, $eb0e363f, $72076785, $05005713,
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+ $95bf4a82, $e2b87a14, $7bb12bae, $0cb61b38, $92d28e9b,
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+ $e5d5be0d, $7cdcefb7, $0bdbdf21, $86d3d2d4, $f1d4e242,
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+ $68ddb3f8, $1fda836e, $81be16cd, $f6b9265b, $6fb077e1,
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+ $18b74777, $88085ae6, $ff0f6a70, $66063bca, $11010b5c,
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+ $8f659eff, $f862ae69, $616bffd3, $166ccf45, $a00ae278,
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+ $d70dd2ee, $4e048354, $3903b3c2, $a7672661, $d06016f7,
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+ $4969474d, $3e6e77db, $aed16a4a, $d9d65adc, $40df0b66,
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+ $37d83bf0, $a9bcae53, $debb9ec5, $47b2cf7f, $30b5ffe9,
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+ $bdbdf21c, $cabac28a, $53b39330, $24b4a3a6, $bad03605,
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+ $cdd70693, $54de5729, $23d967bf, $b3667a2e, $c4614ab8,
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+ $5d681b02, $2a6f2b94, $b40bbe37, $c30c8ea1, $5a05df1b,
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+ $2d02ef8d);
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+
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+{$ENDIF}
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+
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+{ =========================================================================
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+ This function can be used by asm versions of crc32() }
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+
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+function get_crc_table : {const} Pcardinal;
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+begin
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+{$ifdef DYNAMIC_CRC_TABLE}
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+ if (crc_table_empty) then
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+ make_crc_table;
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+{$endif}
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+ get_crc_table := {const} Pcardinal(@crc_table);
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+end;
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+
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+{ ========================================================================= }
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+
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+function crc32 (crc : cardinal; buf : Pbyte; len : cardinal): cardinal;
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+begin
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+ if (buf = nil) then
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+ crc32 := 0
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+ else
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+ begin
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+
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+{$IFDEF DYNAMIC_CRC_TABLE}
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+ if crc_table_empty then
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+ make_crc_table;
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+{$ENDIF}
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+
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+ crc := crc xor cardinal($ffffffff);
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+ while (len >= 8) do
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+ begin
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+ {DO8(buf)}
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+
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+ dec(len, 8);
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+ end;
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+ if (len <> 0) then
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+ repeat
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+ {DO1(buf)}
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+ crc := crc_table[(integer(crc) xor buf^) and $ff] xor (crc shr 8);
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+ inc(buf);
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+
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+ dec(len);
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+ until (len = 0);
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+ crc32 := crc xor cardinal($ffffffff);
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+ end;
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+end;
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+
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+
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+end.
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daniel