www.pudn.com > CRGAB.zip > MEMRITE.ASM
TITLE MEMRITE
PAGE 60,132
;MEMRITE.ASM
COMMENT @
This sub-routine writes directly to video ram on the specified
video page. It first checks for mono text mode, then whether
a VGA or EGA is currently active. If neither is the case
it defaults to CGA.
extern void far pascal memrite(
int atr,int row,int col,int page,int dir,char far *str
);
Can easily be modified for Turbo Pascal 4.0+ by accomodating
Turbo Pascal string format. In fact I debugged this in TP 4.0
and changed the string handling code for C, the " pascal "
function modifier saves me from moving stuff around on the stack
and messing up working code.
Will link with any memory model except tiny
@ Modified ** 10/29/89 ** Michael Kelly
MAXSTR EQU 8192
VMODE EQU BYTE PTR ES:[0049h]
VCOLS EQU WORD PTR ES:[004Ah]
VPAGE_SIZE EQU WORD PTR ES:[004Ch]
VROWS EQU BYTE PTR ES:[0084h]
INFO_BYTE EQU BYTE PTR ES:[0087h]
BYTES_PER_ROW EQU WORD PTR [BP-2] ;local variables
IS_CGA_ADAPT EQU WORD PTR [BP-4]
ATR_PARAM EQU [BP+18] ;proc arguments
ROW_PARAM EQU [BP+16]
COL_PARAM EQU [BP+14]
PAGE_PARAM EQU [BP+12]
DIR_PARAM EQU [BP+10]
STR_PARAM EQU [BP+6]
CSEG SEGMENT BYTE PUBLIC 'CODE'
ASSUME CS:CSEG
PUBLIC MEMRITE
MEMRITE PROC FAR
START: PUSH BP
MOV BP,SP
SUB SP,4
PUSH DS
PUSH SI
PUSH ES
PUSH DI
PUSHF
CLD
XOR CX,CX
MOV IS_CGA_ADAPT,0 ;check the video hardware
MOV DX,0B000h
XOR DI,DI ;assume mono video segment
MOV AX,40h ;and memory ofset of 0 for now.
MOV ES,AX
MOV AL,VMODE
CMP AL,7 ;check video mode
JE MRITE_02
MOV DX,0B800h
CMP AL,3
JBE MRITE_01
JMP EXIT
MRITE_01:
MOV AX,1A00h
INT 10h
CMP AL,1Ah
JNE MRITE_011
CMP BL,2
JNE MRITE_02
MOV IS_CGA_ADAPT,1
JMP SHORT MRITE_02
MRITE_011:
MOV AH,12h
MOV BL,10h
INT 10h
CMP BL,10h
JNE MRITE_012
MOV IS_CGA_ADAPT,1
JMP SHORT MRITE_02
MRITE_012:
MOV AX,40h
MOV ES,AX
TEST INFO_BYTE,8
JZ MRITE_02
MOV IS_CGA_ADAPT,1
MRITE_02: MOV AX,40h
MOV ES,AX
MOV AX,VCOLS
SHL AX,1
MOV BYTES_PER_ROW,AX
MOV BX,PAGE_PARAM ;Calc offset of video page
CMP BX,0 ;using shifts and adds.
JE MRITE_03
MOV AX,VPAGE_SIZE
OR BX,BX
JZ MRITE_03
CMP BX,7
JBE MRITE_021
JMP EXIT ;Assume Max page # is 7.
MRITE_021: CMP BX,1
JA MRITE_022
MOV DI,AX
JMP SHORT MRITE_03
MRITE_022: CMP BX,2
JA MRITE_023
SHL AX,1
MOV DI,AX
JMP SHORT MRITE_03
MRITE_023: CMP BX,3
JA MRITE_024
MOV DI,AX
SHL AX,1
ADD DI,AX
JMP SHORT MRITE_03
MRITE_024: CMP BX,4
JA MRITE_025
SHL AX,1
SHL AX,1
MOV DI,AX
JMP SHORT MRITE_03
MRITE_025: CMP BX,5
JA MRITE_026
MOV DI,AX
SHL AX,1
SHL AX,1
ADD DI,AX
JMP SHORT MRITE_03
MRITE_026: CMP BX,6
JA MRITE_027
SHL AX,1
MOV DI,AX
SHL AX,1
ADD DI,AX
JMP SHORT MRITE_03
MRITE_027: PUSH AX
SHL AX,1
MOV DI,AX
SHL AX,1
ADD DI,AX
POP AX
ADD DI,AX
MRITE_03:
MOV AX,ROW_PARAM ;get screen row and sub 1
DEC AX
JZ MRITE_04
MOV BX,BYTES_PER_ROW
MUL BL ;then mul to get memory offset.
MRITE_04:
MOV BX,COL_PARAM ;throw in video column calc.
XOR BH,BH
DEC BX
SHL BX,1
ADD AX,BX
ADD DI,AX ;sum page row and col to get
MOV ES,DX ;right place in screen memory.
MOV AX,ATR_PARAM
MOV AH,AL
LDS SI,STR_PARAM
MOV CX,MAXSTR
MRITE_05:
CMP IS_CGA_ADAPT,0 ;now we jump to routines depending
JNE MRITE_09 ;on screen writing direction
;and wether we must hassle with a
;Cga video adapter to avoid the
;abominable snow man.
OR BYTE PTR DIR_PARAM,0
JNZ MRITE_07
MRITE_06: LODSB ;horizontal write until
OR AL,AL ;'\0' char found.
JZ EXIT
STOSW
LOOP MRITE_06
JMP EXIT
MRITE_07: LODSB ;vertical write until
OR AL,AL ;'\0' char found.
JZ EXIT
MOV WORD PTR ES:[DI],AX
ADD DI,BYTES_PER_ROW
LOOP MRITE_07
JMP EXIT
;same thing but with
;Cga sync hassle.
MRITE_09: MOV DX,03DAh ;Crt status reg
OR BYTE PTR DIR_PARAM,0 ;to detect retrace sync.
JNZ MRITE_13
MRITE_10: LODSB
OR AL,AL
JZ EXIT ;done if we've found '\0' char.
MOV BX,AX
CLI ;turn off interrupts and use two
MRITE_11: IN AL,DX ;loop to snag start of horiz video sync.
AND AL,1
JNZ MRITE_11
MRITE_12: IN AL,DX
AND AL,1 ;if bit 0 = 1, we're in horiz sync.
JZ MRITE_12
XCHG AX,BX ;get char/attr pair and stuff in memory
STOSW ;during horiz sync.
STI
LOOP MRITE_10 ;repeat until '\0' char found.
JMP EXIT
MRITE_13: ADD DI,2 ;same as above but writes vertcally
MRITE_14: DEC DI ;down the screen.
DEC DI
LODSB
OR AL,AL
JZ EXIT
MRITE_15: MOV BX,AX
CLI
MRITE_16: IN AL,DX
AND AL,1
JNZ MRITE_16
MRITE_17: IN AL,DX
AND AL,1
JZ MRITE_17
XCHG AX,BX
STOSW
STI
ADD DI,BYTES_PER_ROW
LOOP MRITE_14
EXIT:
POPF ;restore flags & regs
POP DI
POP ES
POP SI
POP DS
MOV SP,BP
POP BP
RET 14 ;discard params & return
MEMRITE ENDP
CSEG ENDS
END START