44 lines
981 B
ArmAsm
Executable file
44 lines
981 B
ArmAsm
Executable file
! memcmp() Author: Kees J. Bot
|
|
! 27 Jan 1994
|
|
.sect .text; .sect .rom; .sect .data; .sect .bss
|
|
|
|
! int memcmp(const void *s1, const void *s2, size_t n)
|
|
! Compare two chunks of memory.
|
|
!
|
|
.sect .text
|
|
.define _memcmp
|
|
_memcmp:
|
|
cld
|
|
push bp
|
|
mov bp, sp
|
|
push si
|
|
push di
|
|
xor ax, ax ! Prepare return value
|
|
mov si, 4(bp) ! String s1
|
|
mov di, 6(bp) ! String s2
|
|
mov cx, 8(bp) ! Length
|
|
cmp cx, #16
|
|
jb cbyte ! Don't bother being smart with short arrays
|
|
mov dx, si
|
|
or dx, di
|
|
andb dl, #1
|
|
jnz cbyte ! Bit 0 set, use byte compare
|
|
cword: sar cx, #1
|
|
adcb dl, dl ! Save carry
|
|
repe cmps ! Compare words
|
|
mov cx, #2 ! Recompare the last word
|
|
sub si, cx
|
|
sub di, cx
|
|
addb cl, dl ! One more byte?
|
|
cbyte: test cx, cx ! Set 'Z' flag if cx = 0
|
|
last:
|
|
repe cmpsb ! Look for the first differing byte
|
|
je equal
|
|
ja after
|
|
sub ax, #2 ! if (s1 < s2) ax -= 2;
|
|
after: inc ax ! ax++, now it's -1 or 1
|
|
equal: mov dx, si ! For bcmp() to play with
|
|
pop di
|
|
pop si
|
|
pop bp
|
|
ret
|