Category : Assembly Language Source Code
Archive   : RHSTDLIB.ZIP
Filename : ATOI.ASM

stdlib segment para public 'slcode'
assume cs:stdlib
;
;
; ATOI- Converts the string pointed at by ES:DI to a signed integer value
; and returns this integer in the AX register.
;
; Returns with the carry flag clear if no error, set if overflow.
;
public sl_atoi
sl_atoi proc far
push di
call far ptr sl_atoi2
pop di
ret
sl_atoi endp
;
public sl_atoi2
sl_atoi2 proc far
push cx
push dx
xor cx, cx
mov ah, ch ;Assume it's positive
cmp byte ptr es:[di], '-'
jne DoAtoI
;
; Set up for negative numbers.
;
inc di ;Skip "-"
mov ah, 1 ;Flag negative value.
;
DoAtoI: call NAtoI
jc WasError ;Quit if error.
cmp ah, 0
je IsPositive
neg cx
clc
jmp WasError ;Not really an error.
;
IsPositive: or cx, cx ;See if overflow
clc
jns WasError ;Not an error
stc ;Error if negative.
WasError: mov ax, cx
pop dx
pop cx
ret
sl_atoi2 endp
;
;
;
; ATOU- Just like ATOI but this guy only does unsigned numbers.
;
public sl_atou
sl_atou proc far
push di
call far ptr sl_atou2
pop di
ret
sl_atou endp
;
;
public sl_atou2
sl_atou2 proc far
push cx
push dx
xor cx, cx
call NAtoI
mov ax, cx
pop dx
pop cx
ret
sl_atou2 endp
;
;
;
;
NAtoI proc near
pushf
cld
;
lp: mov al, es:[di] ;Get byte at es:di
inc di
xor al, '0'
cmp al, 10
ja NotDigit
shl cx, 1
jc Error
mov dx, cx
shl cx, 1
jc Error
shl cx, 1
jc Error
add cx, dx
jc Error
add cl, al
adc ch, 0
jc Error
jmp lp
;
NotDigit: popf
clc
ret
;
Error: popf
stc
ret
NAtoI endp
;
stdlib ends
end