source: trunk/minix/lib/i86/string/_strnlen.s@ 9

!       _strnlen()                                      Author: Kees J. Bot
!                                                               27 Jan 1994
.sect .text; .sect .rom; .sect .data; .sect .bss

! size_t _strnlen(const char *s, size_t cx)
!       Return the length of a string.
!
.sect .text
.define __strnlen
__strnlen:
        push    bp
        mov     bp, sp
        push    di
        mov     di, 4(bp)       ! di = string
        xorb    al, al          ! Look for a zero byte
        mov     dx, cx          ! Save maximum count
        cmpb    cl, #1          ! 'Z' bit must be clear if cx = 0
        cld
  repne scasb                   ! Look for zero
        jne     no0
        inc     cx              ! Don't count zero byte
no0:    mov     ax, dx
        sub     ax, cx          ! Compute bytes scanned
        pop     di
        pop     bp
        ret