source: trunk/minix/lib/i386/string/_strncmp.s@ 9

!       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