159 lines
7.2 KiB
NASM
159 lines
7.2 KiB
NASM
;
|
||
; Command & Conquer Red Alert(tm)
|
||
; Copyright 2025 Electronic Arts Inc.
|
||
;
|
||
; This program is free software: you can redistribute it and/or modify
|
||
; it under the terms of the GNU General Public License as published by
|
||
; the Free Software Foundation, either version 3 of the License, or
|
||
; (at your option) any later version.
|
||
;
|
||
; This program is distributed in the hope that it will be useful,
|
||
; but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
; GNU General Public License for more details.
|
||
;
|
||
; You should have received a copy of the GNU General Public License
|
||
; along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||
;
|
||
|
||
;***************************************************************************
|
||
;** 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 **
|
||
;***************************************************************************
|
||
;* *
|
||
;* Project Name : Draw Shape Routines for library. *
|
||
;* *
|
||
;* File Name : DS_LSRS.ASM *
|
||
;* *
|
||
;* Programmer : Scott K. Bowen *
|
||
;* *
|
||
;* Start Date : August 24, 1993 *
|
||
;* *
|
||
;* Last Update : June 2, 1994 [BR] *
|
||
;* *
|
||
;*-------------------------------------------------------------------------*
|
||
;* Functions: *
|
||
;* Left_Scale_Reverse_Skip -- Skips past a scaled row of pixels *
|
||
;* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
|
||
;********************* Model & Processor Directives ************************
|
||
IDEAL
|
||
P386
|
||
MODEL USE32 FLAT
|
||
|
||
|
||
;******************************** Includes *********************************
|
||
INCLUDE "shape.inc"
|
||
|
||
|
||
;********************************* Code ************************************
|
||
CODESEG
|
||
|
||
;***************************************************************************
|
||
;* Left_Scale_Reverse_Skip -- Skips past a scaled row of pixels *
|
||
;* *
|
||
;* INPUT: *
|
||
;* ECX = number of uncompressed bytes to skip *
|
||
;* ESI = shape (source) buffer data address *
|
||
;* EDI = viewport (destination) address *
|
||
;* [WidthCount] = shape's width *
|
||
;* *
|
||
;* OUTPUT: *
|
||
;* ECX - negative # pixels (not bytes) overrun, or 0 *
|
||
;* EDX - XTotal initializer value *
|
||
;* ESI - updated to the current location in the shape data *
|
||
;* EDI - decremented by # pixels (not bytes) overrun *
|
||
;* [WidthCount] - decremented by # bytes skipped *
|
||
;* *
|
||
;* The value returned in EDX reflects what XTotal's accumulated value *
|
||
;* should be at the new pixel location. If no bytes are overrun, this *
|
||
;* will be whatever is stored in [XTotalInit] (which will be 0 if no *
|
||
;* pixels are left-clipped). *
|
||
;* *
|
||
;* WARNINGS: none *
|
||
;* *
|
||
;* HISTORY: *
|
||
;* 04/20/1992 PWG : Created. *
|
||
;* 08/19/1993 SKB : Split drawshp.asm into several modules. *
|
||
;* 06/02/1994 BR : Converted to 32-bit *
|
||
;*=========================================================================*
|
||
PROC Left_Scale_Reverse_Skip NOLANGUAGE NEAR
|
||
|
||
sub [WidthCount],ecx ; we process ECX bytes of real width
|
||
|
||
;--------------------------------------------------------------------
|
||
; Put shape data address in EDI so we can do a scasb on it
|
||
;--------------------------------------------------------------------
|
||
xchg esi,edi ; xchange ESI and EDI
|
||
jcxz ??getrem ; exit if no bytes to skip
|
||
|
||
;--------------------------------------------------------------------
|
||
; Search through the string and count down the info we have handled.
|
||
; If we find a run (0 followed by a count byte), then handle it.
|
||
;--------------------------------------------------------------------
|
||
??cliptop:
|
||
mov eax,0 ; set al to 0 (we're scanning for 0)
|
||
repne scasb ; scan through source data
|
||
jz short ??on_run ; if it is a run then deal with it
|
||
|
||
;--------------------------------------------------------------------
|
||
; Default exit point: store default x-scale bits & exit
|
||
;--------------------------------------------------------------------
|
||
??getrem:
|
||
mov edx,[XTotalInit] ; store out the remainder
|
||
jmp short ??out ; we're done, get outta here
|
||
|
||
;--------------------------------------------------------------------
|
||
; If we have a run then get the next byte which is the length.
|
||
;--------------------------------------------------------------------
|
||
??on_run:
|
||
mov al,[BYTE PTR edi] ; get the count of zeros to run
|
||
inc edi ; advance past the count
|
||
inc ecx ; the 0 found doesn't count
|
||
sub ecx,eax ; subtract the count from remaining
|
||
jg ??cliptop ; if more bytes left, scan again
|
||
jz ??getrem ; exactly enough bytes; exit
|
||
|
||
;--------------------------------------------------------------------
|
||
; Overrun exit point: ECX is negative by the # of bytes overrun.
|
||
; - adjust [WidthCount] by # of overrun bytes
|
||
; - compute the remainder at the new location (EDX)
|
||
; - compute the number of destination pixels to skip (ECX)
|
||
; - adjust EDI by # of overrun bytes
|
||
;--------------------------------------------------------------------
|
||
;
|
||
;............... adjust [WidthCount] by overrun bytes ...............
|
||
;
|
||
add [WidthCount],ecx ; adjust overrun in bytes
|
||
;
|
||
;................. put x-scale roundoff bits in EDX .................
|
||
;
|
||
mov eax,ecx ; get the number of bytes we overran
|
||
neg eax ; negate it since overun is negative
|
||
add eax,[LeftClipBytes] ; add the number of bytes we leftclip
|
||
mul [ScaleX] ; convert to pixels plus roundoff bits
|
||
mov edx,0 ; clear EDX
|
||
mov dl,al ; DL = x-scaling roundoff bits
|
||
;
|
||
;................ put negative overrun pixels in ECX ................
|
||
;
|
||
shr eax,8 ; EAX = total # left pixels
|
||
sub eax,[LeftClipPixels] ; EAX = # pixels overrun
|
||
mov ecx,eax ; store # overrun pixels
|
||
neg ecx ; make it negative
|
||
;
|
||
;................ adjust dest ptr by overrun pixels .................
|
||
;
|
||
sub esi,eax ; decrement ESI (EDI) by overrun pixels
|
||
|
||
;--------------------------------------------------------------------
|
||
; Put shape address back into ESI, adjust EDI
|
||
;--------------------------------------------------------------------
|
||
??out:
|
||
xchg esi,edi ; xchange ESI and EDI
|
||
ret ; return back to the real function
|
||
|
||
ENDP Left_Scale_Reverse_Skip
|
||
|
||
END
|
||
|
||
;**************************** End of ds_lsrs.asm ****************************
|
||
|