193 lines
7.9 KiB
NASM
193 lines
7.9 KiB
NASM
IDEAL
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; This CRC-32 routine and tables were converted from code discovered
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; in the DEZIP.PAS V2.0 by R. P. Byrne. The comments there are:
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;
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; Converted to Turbo Pascal (tm) V4.0 March, 1988 by J.R.Louvau
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; COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or
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; code or tables extracted from it, as desired without restriction.
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;
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; First, the polynomial itself and its table of feedback terms. The
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; polynomial is
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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+X^0
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;
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; Note that we take it "backwards" and put the highest-order term in
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; the lowest-order bit. The X^32 term is "implied"; the LSB is the
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; X^31 term, etc. The X^0 term (usually shown as "+1") results in
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; the MSB being 1.
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;
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; Note that the usual hardware shift register implementation, which
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; is what we're using (we're merely optimizing it by doing eight-bit
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; chunks at a time) shifts bits into the lowest-order term. In our
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; implementation, that means shifting towards the right. Why do we
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; do it this way? Because the calculated CRC must be transmitted in
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; order from highest-order term to lowest-order term. UARTs transmit
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; characters in order from LSB to MSB. By storing the CRC this way,
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; we hand it to the UART in the order low-byte to high-byte; the UART
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; sends each low-bit to high-bit; and the result is transmission bit
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; by bit from highest- to lowest-order term without requiring any bit
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; shuffling on our part. Reception works similarly.
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;
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; The feedback terms table consists of 256, 32-bit entries. Notes:
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;
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; The table can be generated at runtime if desired; code to do so
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; is shown later. It might not be obvious, but the feedback
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; terms simply represent the results of eight shift/xor opera-
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; tions for all combinations of data and CRC register values.
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;
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; The values must be right-shifted by eight bits by the "updcrc"
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; logic; the shift must be unsigned (bring in zeroes). On some
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; hardware you could probably optimize the shift in assembler by
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; using byte-swap instructions.
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; polynomial $edb88320
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;
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; <End of Pascal version comments>
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;
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; The Pascal logic is:
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;
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; Function UpdC32(Octet: Byte; Crc: LongInt) : LongInt;
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; Begin
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;
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; UpdC32 := CRC_32_TAB[Byte(Crc XOR LongInt(Octet))] XOR ((Crc SHR 8)
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; AND $00FFFFFF);
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;
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; End {UpdC32};
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;
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; This routine computes the 32 bit CRC used by PKZIP and its derivatives,
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; and by Chuck Forsberg's "ZMODEM" protocol. The block CRC computation
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; should start with high-values (0ffffffffh), and finish by inverting all
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; bits.
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;
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; This TASM conversion done by:
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;
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; Edwin T. Floyd [76067,747]
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; #9 Adams Park Ct.
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; Columbus, GA 31909
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; 404-576-3305 (work)
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; 404-322-0076 (home)
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;
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; Borland's Turbo Assembler - TASM is required to assemble this program.
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;
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SEGMENT code BYTE PUBLIC
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ASSUME cs:code
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; 0
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crc32tab dd 000000000h, 077073096h, 0ee0e612ch, 0990951bah
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dd 0076dc419h, 0706af48fh, 0e963a535h, 09e6495a3h
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dd 00edb8832h, 079dcb8a4h, 0e0d5e91eh, 097d2d988h
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dd 009b64c2bh, 07eb17cbdh, 0e7b82d07h, 090bf1d91h
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; 1
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dd 01db71064h, 06ab020f2h, 0f3b97148h, 084be41deh
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dd 01adad47dh, 06ddde4ebh, 0f4d4b551h, 083d385c7h
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dd 0136c9856h, 0646ba8c0h, 0fd62f97ah, 08a65c9ech
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dd 014015c4fh, 063066cd9h, 0fa0f3d63h, 08d080df5h
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; 2
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dd 03b6e20c8h, 04c69105eh, 0d56041e4h, 0a2677172h
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dd 03c03e4d1h, 04b04d447h, 0d20d85fdh, 0a50ab56bh
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dd 035b5a8fah, 042b2986ch, 0dbbbc9d6h, 0acbcf940h
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dd 032d86ce3h, 045df5c75h, 0dcd60dcfh, 0abd13d59h
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; 3
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dd 026d930ach, 051de003ah, 0c8d75180h, 0bfd06116h
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dd 021b4f4b5h, 056b3c423h, 0cfba9599h, 0b8bda50fh
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dd 02802b89eh, 05f058808h, 0c60cd9b2h, 0b10be924h
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dd 02f6f7c87h, 058684c11h, 0c1611dabh, 0b6662d3dh
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; 4
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dd 076dc4190h, 001db7106h, 098d220bch, 0efd5102ah
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dd 071b18589h, 006b6b51fh, 09fbfe4a5h, 0e8b8d433h
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dd 07807c9a2h, 00f00f934h, 09609a88eh, 0e10e9818h
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dd 07f6a0dbbh, 0086d3d2dh, 091646c97h, 0e6635c01h
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; 5
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dd 06b6b51f4h, 01c6c6162h, 0856530d8h, 0f262004eh
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dd 06c0695edh, 01b01a57bh, 08208f4c1h, 0f50fc457h
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dd 065b0d9c6h, 012b7e950h, 08bbeb8eah, 0fcb9887ch
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dd 062dd1ddfh, 015da2d49h, 08cd37cf3h, 0fbd44c65h
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; 6
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dd 04db26158h, 03ab551ceh, 0a3bc0074h, 0d4bb30e2h
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dd 04adfa541h, 03dd895d7h, 0a4d1c46dh, 0d3d6f4fbh
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dd 04369e96ah, 0346ed9fch, 0ad678846h, 0da60b8d0h
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dd 044042d73h, 033031de5h, 0aa0a4c5fh, 0dd0d7cc9h
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; 7
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dd 05005713ch, 0270241aah, 0be0b1010h, 0c90c2086h
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dd 05768b525h, 0206f85b3h, 0b966d409h, 0ce61e49fh
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dd 05edef90eh, 029d9c998h, 0b0d09822h, 0c7d7a8b4h
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dd 059b33d17h, 02eb40d81h, 0b7bd5c3bh, 0c0ba6cadh
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; 8
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dd 0edb88320h, 09abfb3b6h, 003b6e20ch, 074b1d29ah
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dd 0ead54739h, 09dd277afh, 004db2615h, 073dc1683h
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dd 0e3630b12h, 094643b84h, 00d6d6a3eh, 07a6a5aa8h
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dd 0e40ecf0bh, 09309ff9dh, 00a00ae27h, 07d079eb1h
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; 9
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dd 0f00f9344h, 08708a3d2h, 01e01f268h, 06906c2feh
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dd 0f762575dh, 0806567cbh, 0196c3671h, 06e6b06e7h
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dd 0fed41b76h, 089d32be0h, 010da7a5ah, 067dd4acch
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dd 0f9b9df6fh, 08ebeeff9h, 017b7be43h, 060b08ed5h
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; A
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dd 0d6d6a3e8h, 0a1d1937eh, 038d8c2c4h, 04fdff252h
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dd 0d1bb67f1h, 0a6bc5767h, 03fb506ddh, 048b2364bh
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dd 0d80d2bdah, 0af0a1b4ch, 036034af6h, 041047a60h
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dd 0df60efc3h, 0a867df55h, 0316e8eefh, 04669be79h
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; B
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dd 0cb61b38ch, 0bc66831ah, 0256fd2a0h, 05268e236h
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dd 0cc0c7795h, 0bb0b4703h, 0220216b9h, 05505262fh
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dd 0c5ba3bbeh, 0b2bd0b28h, 02bb45a92h, 05cb36a04h
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dd 0c2d7ffa7h, 0b5d0cf31h, 02cd99e8bh, 05bdeae1dh
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; C
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dd 09b64c2b0h, 0ec63f226h, 0756aa39ch, 0026d930ah
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dd 09c0906a9h, 0eb0e363fh, 072076785h, 005005713h
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dd 095bf4a82h, 0e2b87a14h, 07bb12baeh, 00cb61b38h
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dd 092d28e9bh, 0e5d5be0dh, 07cdcefb7h, 00bdbdf21h
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; D
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dd 086d3d2d4h, 0f1d4e242h, 068ddb3f8h, 01fda836eh
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dd 081be16cdh, 0f6b9265bh, 06fb077e1h, 018b74777h
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dd 088085ae6h, 0ff0f6a70h, 066063bcah, 011010b5ch
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dd 08f659effh, 0f862ae69h, 0616bffd3h, 0166ccf45h
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; E
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dd 0a00ae278h, 0d70dd2eeh, 04e048354h, 03903b3c2h
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dd 0a7672661h, 0d06016f7h, 04969474dh, 03e6e77dbh
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dd 0aed16a4ah, 0d9d65adch, 040df0b66h, 037d83bf0h
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dd 0a9bcae53h, 0debb9ec5h, 047b2cf7fh, 030b5ffe9h
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; F
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dd 0bdbdf21ch, 0cabac28ah, 053b39330h, 024b4a3a6h
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dd 0bad03605h, 0cdd70693h, 054de5729h, 023d967bfh
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dd 0b3667a2eh, 0c4614ab8h, 05d681b02h, 02a6f2b94h
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dd 0b40bbe37h, 0c30c8ea1h, 05a05df1bh, 02d02ef8dh
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MODEL TPASCAL
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PUBLIC UpdateCRC32
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PROC UpdateCRC32 FAR initcrc:DWORD,inbuf:DWORD,inlen:WORD
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; UpdateCRC32 takes an initial CRC value and updates it with inlen bytes from
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; inbuf. The updated CRC is returned in DX:AX. The Pascal declaration is:
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; Function UpdateCRC32(InitCRC : LongInt; Var InBuf; InLen : Word) : LongInt;
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; Stomps registers: AX,BX,CX,DX,ES,SI
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push ds
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lds si,[inbuf] ; ds:si := ^inbuf
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les ax,[initcrc] ; dx:ax := initcrc
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mov dx,es
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mov cx,[inlen] ; cx := inlen
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or cx,cx
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jz @@done
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@@loop:
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xor bh,bh
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mov bl,al
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lodsb
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xor bl,al
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mov al,ah
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mov ah,dl
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mov dl,dh
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xor dh,dh
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shl bx,1
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shl bx,1
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les bx,[crc32tab+bx]
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xor ax,bx
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mov bx,es
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xor dx,bx
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loop @@loop
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@@done:
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pop ds
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ret
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ENDP
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ENDS
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END
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