minix/lib/libc/arch/arm/string/strncat_naive.S

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/*-
* Copyright (c) 2013 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Matt Thomas of 3am Software Foundry.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
#include <machine/asm.h>
RCSID("$NetBSD: strncat_naive.S,v 1.1 2013/01/23 05:44:52 matt Exp $")
/* LINTSTUB: char *strncat(char *, const char *, size_t) */
ENTRY(strncat)
teq r2, #0 /* count is 0? */
RETc(eq) /* yes, just return dst */
mov ip, r0 /* need to preserve r0 */
1: ldrb r3, [ip], #1 /* load next byte */
teq r3, #0 /* was it a NUL? */
bne 1b /* no, get next byte */
sub ip, ip, #1 /* back up one to the NUL */
2: subs r2, r2, #1 /* subtract 1 from the count */
blt 3f /* <0? write terminating NUL */
ldrb r3, [r1], #1 /* load next byte from append */
strb r3, [ip], #1 /* store it */
teq r3, #0 /* was it a NUL? */
bne 2b /* no, get next byte */
RET /* return */
3: mov r3, #0 /* load a NUL */
strb r3, [ip] /* store it */
RET /* return */
END(strncat)