114 lines
3.0 KiB
NASM
114 lines
3.0 KiB
NASM
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; Command & Conquer Red Alert(tm)
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; Copyright 2025 Electronic Arts Inc.
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;
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;***************************************************************************
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;** C O N F I D E N T I A L --- W E S T W O O D A S S O C I A T E S **
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;***************************************************************************
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;* *
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;* Project Name : Westwood Library *
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;* *
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;* File Name : CRC.ASM *
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;* *
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;* Programmer : Joe L. Bostic *
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;* *
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;* Start Date : June 12, 1992 *
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;* *
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;* Last Update : February 10, 1995 [BWG] *
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;* *
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;*-------------------------------------------------------------------------*
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;* Functions: *
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;* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
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IDEAL
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P386
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MODEL USE32 FLAT
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GLOBAL C Calculate_CRC :NEAR
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CODESEG
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; LONG Calculate_CRC(VOID *buffer, LONG length);
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PROC Calculate_CRC C near
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USES esi
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ARG buffer:DWORD
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ARG length:DWORD
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LOCAL crc:DWORD
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; Load pointer to data block.
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mov [crc],0
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pushad
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mov esi,[buffer]
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cld
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; Clear CRC to default (NULL) value.
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xor ebx,ebx
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; Fetch the length of the data block to CRC.
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mov ecx,[length]
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jecxz short ??fini
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; Prepare the length counters.
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mov edx,ecx
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and dl,011b
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shr ecx,2
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; Perform the bulk of the CRC scanning.
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jecxz short ??remainder
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??accumloop:
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lodsd
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rol ebx,1
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add ebx,eax
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loop ??accumloop
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; Handle the remainder bytes.
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??remainder:
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or dl,dl
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jz short ??fini
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mov ecx,edx
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xor eax,eax
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and ecx,0FFFFh
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push ecx
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??nextbyte:
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lodsb
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ror eax,8
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loop ??nextbyte
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pop ecx
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neg ecx
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add ecx,4
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shl ecx,3
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ror eax,cl
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;??nextbyte:
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; shl eax,8
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; lodsb
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; loop ??nextbyte
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rol ebx,1
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add ebx,eax
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??fini:
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mov [crc],ebx
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popad
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mov eax,[crc]
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ret
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ENDP Calculate_CRC
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END
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