135 lines
6.8 KiB
NASM
135 lines
6.8 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 S T U D I O S I N C **
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;***************************************************************************
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;* *
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;* Project Name : Command & Conquer *
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;* *
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;* File Name : COORDA.ASM *
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;* *
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;* Programmer : Barry W. Green *
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;* *
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;* Start Date : February 17, 1995 *
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;* *
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;* Last Update : February 17, 1995 [BWG] *
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;* *
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;*-------------------------------------------------------------------------*
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;* Functions: *
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;* Cardinal_To_Fixed -- Converts cardinal numbers into a fixed point number. *
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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 Cardinal_To_Fixed :NEAR
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GLOBAL Fixed_To_Cardinal :NEAR
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CODESEG
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;***********************************************************************************************
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;* Cardinal_To_Fixed -- Converts cardinal numbers into a fixed point number. *
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;* *
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;* This utility function will convert cardinal numbers into a fixed point fraction. The *
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;* use of fixed point numbers occurs throughout the product -- since it is a convenient *
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;* tool. The fixed point number is based on the formula: *
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;* *
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;* result = cardinal / base *
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;* *
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;* The accuracy of the fixed point number is limited to 1/256 as the lowest and up to *
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;* 256 as the largest. *
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;* *
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;* INPUT: base -- The key number to base the fraction about. *
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;* *
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;* cardinal -- The other number (hey -- what do you call it?) *
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;* *
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;* OUTPUT: Returns with the fixed point number of the "cardinal" parameter as it relates *
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;* to the "base" parameter. *
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;* *
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;* WARNINGS: none *
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;* *
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;* HISTORY: *
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;* 02/17/1995 BWG : Created. *
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;*=============================================================================================*/
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;unsigned int Cardinal_To_Fixed(unsigned base, unsigned cardinal);
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PROC Cardinal_To_Fixed C near
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USES ebx, edx
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ARG base:DWORD
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ARG cardinal:DWORD
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mov eax,0FFFFh ; establish default return value
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mov ebx,[base]
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or ebx,ebx
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jz near ??retneg1 ; if base==0, return 65535
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mov eax,[cardinal] ; otherwise, return (cardinal*256)/base
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shl eax,8
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xor edx,edx
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div ebx
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??retneg1:
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ret
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ENDP Cardinal_To_Fixed
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;***********************************************************************************************
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;* Fixed_To_Cardinal -- Converts a fixed point number into a cardinal number. *
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;* *
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;* Use this routine to convert a fixed point number into a cardinal number. *
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;* *
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;* INPUT: base -- The base number that the original fixed point number was created from. *
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;* *
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;* fixed -- The fixed point number to convert. *
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;* *
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;* OUTPUT: Returns with the reconverted number. *
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;* *
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;* WARNINGS: none *
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;* *
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;* HISTORY: *
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;* 02/17/1995 BWG : Created. *
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;*=============================================================================================*/
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;unsigned int Fixed_To_Cardinal(unsigned base, unsigned fixed);
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PROC Fixed_To_Cardinal C near
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USES edx
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ARG base:DWORD
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ARG fixed:DWORD
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mov eax,[base]
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mul [fixed]
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add eax,080h ; eax = (base * fixed) + 0x80
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test eax,0FF000000h ; if high byte set, return FFFF
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jnz ??rneg1
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shr eax,8 ; else, return eax/256
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ret
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??rneg1 :
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mov eax,0FFFFh ; establish default return value
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ret
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ENDP Fixed_To_Cardinal
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END
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