strncat.s

早期freebsd实现

/*
 * Copyright (c) 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This code is derived from software contributed to Berkeley by
 * Computer Consoles Inc.
 */

#if defined(LIBC_SCCS) && !defined(lint)
	.asciz "@(#)strncat.s	8.1 (Berkeley) 6/4/93"
#endif /* LIBC_SCCS and not lint */

/*
 * Concatenate s2 on the end of s1.  S1's space must be large enough.
 * At most n characters are moved.
 * Return s1.
 * 
 * char *strncat(s1, s2, n)
 * register char *s1, *s2;
 * register n;
 */
#include "DEFS.h"

ENTRY(strncat, 0)
	tstl	12(fp)
	jgtr	n_ok
	movl	4(fp),r0
	ret
n_ok:
	movl	8(fp),r0
	movl	r0,r1
	cmps2			# r0 points at null at end of s2
	subl3	8(fp),r0,r2	# r2 = numberof non-null chars in s2
	cmpl	12(fp),r2
	jgeq	r2_ok
	movl	12(fp),r2	# r2 = min (n, length(s2))
r2_ok:
	movl	4(fp),r0
	movl	r0,r1
	cmps2			# r1 points at null at end of s1
	movl	8(fp),r0	# source for copy
	movs3			# actual copy
	clrb	(r1)		# null terminated string !
	movl	4(fp),r0
	ret