minix/lib/i86/string/_strncat.s

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2005-04-21 16:53:53 +02:00
! _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