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

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

! char *_strncat(char *s1, const char *s2, size_t dx)
!       Append string s2 to s1.
!
.sect .text
.define __strncat
__strncat:
        push    bp
        mov     bp, sp
        push    si
        push    di
        mov     di, 4(bp)       ! String s1
        mov     cx, #-1
        xorb    al, al          ! Null byte
        cld
  repne scasb                   ! Look for the zero byte in s1
        dec     di              ! Back one up (and clear 'Z' flag)
        push    di              ! Save end of s1
        mov     di, 6(bp)       ! di = string s2
        mov     cx, dx          ! Maximum count
  repne scasb                   ! Look for the end of s2
        jne     no0
        inc     cx              ! Exclude null byte
no0:    sub     dx, cx          ! Number of bytes in s2
        mov     cx, dx
        mov     si, 6(bp)       ! si = string s2
        pop     di              ! di = end of string s1
    rep movsb                   ! Copy bytes
        stosb                   ! Add a terminating null
        mov     ax, 4(bp)       ! Return s1
        pop     di
        pop     si
        pop     bp
        ret