minix/lib/i386/string/_strncmp.s

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2005-04-21 16:53:53 +02:00
! strncmp() Author: Kees J. Bot
! 1 Jan 1994
.sect .text; .sect .rom; .sect .data; .sect .bss
! int strncmp(const char *s1, const char *s2, size_t ecx)
! Compare two strings.
!
.sect .text
.define __strncmp
.align 16
__strncmp:
push ebp
mov ebp, esp
push esi
push edi
test ecx, ecx ! Max length is zero?
je done
mov esi, 8(ebp) ! esi = string s1
mov edi, 12(ebp) ! edi = string s2
cld
compare:
cmpsb ! Compare two bytes
jne done
cmpb -1(esi), 0 ! End of string?
je done
dec ecx ! Length limit reached?
jne compare
done: seta al ! al = (s1 > s2)
setb ah ! ah = (s1 < s2)
subb al, ah
movsxb eax, al ! eax = (s1 > s2) - (s1 < s2), i.e. -1, 0, 1
pop edi
pop esi
pop ebp
ret