1 UNIT crc32;
2
3 {$I-}
4 {$V-}
5 {$S+}
6 {$F+}
7 { $D-}
8 { $L-}
9 {$R-}
10 {$X+}
11
12 {$IFNDEF WINDOWS}
13 {$O+} {Make units overlayable}
14 {$X-} {Turn off extended syntax}
15 {$ENDIF}
16
17 {$IFDEF WINDOWS}
18 {$DEFINE BASMINT} {Use BASM for interrupts under windows}
19 {$ENDIF}
20
21 {. $DEFINE OPRO} {Remove dot to use with OPRO}
22
23 INTERFACE
24
25 { Use a type LONGINT variable to store the crc value. }
26 { Initialise the variable to $FFFFFFFF before running the crc routine. }
27 { VERY IMPORTANT!!!! -> This routine was developed for data communications}
28 { and returns the crc bytes in LOW to HIGH order, NOT byte reversed! }
29 { To turn the valu into a 'normal' LONGINT, you must reverse the bytes! }
30 { e.g. }
31 { VAR }
32 { l, crc: LONGINT; }
33 { list: ARRAY[0..1023] OF BYTE; }
34 { counter: INTEGER; }
35 { }
36 { BEGIN }
37 { crc := $FFFFFFFF; (* initialise *) }
38 { FillChar(list,SizeOf(list),1); (* dummy array *) }
39 { FOR counter := 0 TO (Pred(SizeOf(list))) DO (* run thru *) }
40 { crc := UpdC32(buf[counter],crc); (* finding crc *) }
41 { FOR counter := 1 TO 4 DO (* reverse *) }
42 { l := (l SHL 8) OR BYTE(crc); (* the bytes *) }
43 { (* l now contains the 'normalized' crc *) }
44 { }
45
UpdC32null46 FUNCTION UpdC32(octet: BYTE; crc: LONGINT) : LONGINT;
47
48 IMPLEMENTATION
49 (* Converted to Turbo Pascal (tm) V4.0 March, 1988 by J.R.Louvau *)
50 (* Copyright (C) 1986 Gary S. Brown. You may use this program, or *)
51 (* code or tables extracted from it, as desired without restriction. *)
52 (* *)
53 (* First, the polynomial itself and its table of feedback terms. The *)
54 (* polynomial is *)
55 (* 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+X^0 *)
56 (* Note that we take it "backwards" and put the highest-order term in *)
57 (* the lowest-order bit. The X^32 term is "implied"; the LSB is the *)
58 (* X^31 term, etc. The X^0 term (usually shown as "+1") results in *)
59 (* the MSB being 1. *)
60 (* *)
61 (* Note that the usual hardware shift register implementation, which *)
62 (* is what we're using (we're merely optimizing it by doing eight-bit *)
63 (* chunks at a time) shifts bits into the lowest-order term. In our *)
64 (* implementation, that means shifting towards the right. Why do we *)
65 (* do it this way? Because the calculated CRC must be transmitted in *)
66 (* order from highest-order term to lowest-order term. UARTs transmit *)
67 (* characters in order from LSB to MSB. By storing the CRC this way, *)
68 (* we hand it to the UART in the order low-byte to high-byte; the UART *)
69 (* sends each low-bit to hight-bit; and the result is transmission bit *)
70 (* by bit from highest- to lowest-order term without requiring any bit *)
71 (* shuffling on our part. Reception works similarly. *)
72 (* *)
73 (* The feedback terms table consists of 256, 32-bit entries. Notes: *)
74 (* *)
75 (* The table can be generated at runtime if desired; code to do so *)
76 (* is shown later. It might not be obvious, but the feedback *)
77 (* terms simply represent the results of eight shift/xor opera- *)
78 (* tions for all combinations of data and CRC register values. *)
79 (* *)
80 (* The values must be right-shifted by eight bits by the "updcrc" *)
81 (* logic; the shift must be unsigned (bring in zeroes). On some *)
82 (* hardware you could probably optimize the shift in assembler by *)
83 (* using byte-swap instructions. *)
84 (* polynomial $edb88320 *)
85 (* *)
86
87
88
89 CONST crc_32_tab: ARRAY[0..255] OF LONGINT = (
90 $00000000, $77073096, $ee0e612c, $990951ba, $076dc419, $706af48f, $e963a535, $9e6495a3,
91 $0edb8832, $79dcb8a4, $e0d5e91e, $97d2d988, $09b64c2b, $7eb17cbd, $e7b82d07, $90bf1d91,
92 $1db71064, $6ab020f2, $f3b97148, $84be41de, $1adad47d, $6ddde4eb, $f4d4b551, $83d385c7,
93 $136c9856, $646ba8c0, $fd62f97a, $8a65c9ec, $14015c4f, $63066cd9, $fa0f3d63, $8d080df5,
94 $3b6e20c8, $4c69105e, $d56041e4, $a2677172, $3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b,
95 $35b5a8fa, $42b2986c, $dbbbc9d6, $acbcf940, $32d86ce3, $45df5c75, $dcd60dcf, $abd13d59,
96 $26d930ac, $51de003a, $c8d75180, $bfd06116, $21b4f4b5, $56b3c423, $cfba9599, $b8bda50f,
97 $2802b89e, $5f058808, $c60cd9b2, $b10be924, $2f6f7c87, $58684c11, $c1611dab, $b6662d3d,
98 $76dc4190, $01db7106, $98d220bc, $efd5102a, $71b18589, $06b6b51f, $9fbfe4a5, $e8b8d433,
99 $7807c9a2, $0f00f934, $9609a88e, $e10e9818, $7f6a0dbb, $086d3d2d, $91646c97, $e6635c01,
100 $6b6b51f4, $1c6c6162, $856530d8, $f262004e, $6c0695ed, $1b01a57b, $8208f4c1, $f50fc457,
101 $65b0d9c6, $12b7e950, $8bbeb8ea, $fcb9887c, $62dd1ddf, $15da2d49, $8cd37cf3, $fbd44c65,
102 $4db26158, $3ab551ce, $a3bc0074, $d4bb30e2, $4adfa541, $3dd895d7, $a4d1c46d, $d3d6f4fb,
103 $4369e96a, $346ed9fc, $ad678846, $da60b8d0, $44042d73, $33031de5, $aa0a4c5f, $dd0d7cc9,
104 $5005713c, $270241aa, $be0b1010, $c90c2086, $5768b525, $206f85b3, $b966d409, $ce61e49f,
105 $5edef90e, $29d9c998, $b0d09822, $c7d7a8b4, $59b33d17, $2eb40d81, $b7bd5c3b, $c0ba6cad,
106 $edb88320, $9abfb3b6, $03b6e20c, $74b1d29a, $ead54739, $9dd277af, $04db2615, $73dc1683,
107 $e3630b12, $94643b84, $0d6d6a3e, $7a6a5aa8, $e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1,
108 $f00f9344, $8708a3d2, $1e01f268, $6906c2fe, $f762575d, $806567cb, $196c3671, $6e6b06e7,
109 $fed41b76, $89d32be0, $10da7a5a, $67dd4acc, $f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5,
110 $d6d6a3e8, $a1d1937e, $38d8c2c4, $4fdff252, $d1bb67f1, $a6bc5767, $3fb506dd, $48b2364b,
111 $d80d2bda, $af0a1b4c, $36034af6, $41047a60, $df60efc3, $a867df55, $316e8eef, $4669be79,
112 $cb61b38c, $bc66831a, $256fd2a0, $5268e236, $cc0c7795, $bb0b4703, $220216b9, $5505262f,
113 $c5ba3bbe, $b2bd0b28, $2bb45a92, $5cb36a04, $c2d7ffa7, $b5d0cf31, $2cd99e8b, $5bdeae1d,
114 $9b64c2b0, $ec63f226, $756aa39c, $026d930a, $9c0906a9, $eb0e363f, $72076785, $05005713,
115 $95bf4a82, $e2b87a14, $7bb12bae, $0cb61b38, $92d28e9b, $e5d5be0d, $7cdcefb7, $0bdbdf21,
116 $86d3d2d4, $f1d4e242, $68ddb3f8, $1fda836e, $81be16cd, $f6b9265b, $6fb077e1, $18b74777,
117 $88085ae6, $ff0f6a70, $66063bca, $11010b5c, $8f659eff, $f862ae69, $616bffd3, $166ccf45,
118 $a00ae278, $d70dd2ee, $4e048354, $3903b3c2, $a7672661, $d06016f7, $4969474d, $3e6e77db,
119 $aed16a4a, $d9d65adc, $40df0b66, $37d83bf0, $a9bcae53, $debb9ec5, $47b2cf7f, $30b5ffe9,
120 $bdbdf21c, $cabac28a, $53b39330, $24b4a3a6, $bad03605, $cdd70693, $54de5729, $23d967bf,
121 $b3667a2e, $c4614ab8, $5d681b02, $2a6f2b94, $b40bbe37, $c30c8ea1, $5a05df1b, $2d02ef8d
122 );
123
UpdC32null124 FUNCTION UpdC32(octet: BYTE; crc: LONGINT) : LONGINT;
125 BEGIN { UpdC32 }
126 UpdC32 := crc_32_tab[BYTE(crc XOR LONGINT(octet))] XOR ((crc SHR 8) AND $00FFFFFF)
127 END;
128
129 END. {unit}
130