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strlen_naive.S revision 1.7 
      1 /*-
      2  * Copyright (c) 2013 The NetBSD Foundation, Inc.
      3  * All rights reserved.
      4  *
      5  * This code is derived from software contributed to The NetBSD Foundation
      6  * by Matt Thomas of 3am Software Foundry.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     19  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     20  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     21  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     22  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     23  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     24  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     25  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     26  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     27  * POSSIBILITY OF SUCH DAMAGE.
     28  */
     29 #include <machine/asm.h>
     30 
     31 RCSID("$NetBSD: strlen_naive.S,v 1.7 2013/08/19 02:13:13 matt Exp $")
     32 
     33 #ifdef STRNLEN
     34 /* LINTSTUB: size_t strnlen(const char *, size_t) */
     35 ENTRY(strnlen)
     36 	adds	r3, r0, #1	/* start of src + NUL */
     37 #ifdef __thumb__
     38 	adds	r2, r0, r1	/* &src[maxlen] */
     39 	mov	ip, r2
     40 #else
     41 	adds	ip, r0, r1	/* &src[maxlen] */
     42 #endif
     43 1:	cmp	r0, ip		/* is this of string? */
     44 	beq	2f		/*   yes it is */
     45 #ifdef __thumb__
     46 	ldrb	r2, [r0]	/* read a byte */
     47 	adds	r0, r0, #1	/* advance to next byte */
     48 #else
     49 	ldrb	r2, [r0], #1	/* read a byte */
     50 #endif
     51 	cmp	r2, #0		/* is it a NUL? */
     52 	bne	1b		/*   no, get next byte */
     53 	subs	r0, r0, r3	/* get difference between start and end */
     54 	RET			/* return */
     55 2:	mov	r0, r1		/* get maxlen */
     56 	RET			/* return */
     57 END(strnlen)
     58 #else /* STRNLEN */
     59 /* LINTSTUB: size_t strlen(const char *) */
     60 ENTRY(strlen)
     61 	adds	r2, r0, #1	/* start of src + NUL */
     62 1:
     63 #ifdef __thumb__
     64 	ldrb	r3, [r0]	/* read a byte */
     65 	adds	r0, r0, #1
     66 #else
     67 	ldrb	r3, [r0], #1	/* read a byte */
     68 #endif
     69 	cmp	r3, #0		/* is it a NUL? */
     70 	bne	1b		/*   no, get next byte */
     71 	subs	r0, r0, r2	/* return difference between start and end */
     72 	RET
     73 END(strlen)
     74 #endif /* !STRNLEN */
     75