root/common/lib/libc/arch/arm/string/strcpy_thumb.S
/*-
 * 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: strcpy_thumb.S,v 1.3 2017/01/14 03:00:13 christos Exp $")

#ifdef _LIBC
#ifdef STRLCPY
WEAK_ALIAS(strlcpy, _strlcpy)
#define strlcpy _strlcpy
#endif
#ifdef STRNCPY
WEAK_ALIAS(strncpy, _strncpy)
#define strncpy _strncpy
#endif
#ifdef STRCPY
WEAK_ALIAS(strcpy, _strcpy)
#define strcpy _strcpy
#endif
#endif

/*
 * These are "naive" versions of the str*cpy routines designed to be simple
 * and small.
 */

#if defined(STRLCPY)
/* LINTSTUB: size_t strlcpy(char *, const char *, size_t) */
ENTRY(strlcpy)
        adds    r3, r1, #1              /* save src pointer (+ NUL) */
        subs    r2, r2, #1              /* make sure there's room for a NUL */
        blt     3f                      /*   no room, do the strlen */
        adds    r2, r2, r0              /* get end of dst */
        subs    r0, r0, r1              /* bias against r1 so one incr */
1:      cmp     r0, r2                  /* room for another char? */
        beq     2f                      /*   no, write NUL and do the strlen */
        ldrb    r3, [r1]                /* read a byte */
        strb    r3, [r0, r1]            /* write a byte */
        adds    r1, r1, #1              /* advance to next byte */
        cmp     r3, #0                  /* was it a NUL? */
        bne     1b                      /*   no, do next byte */
        b       4f                      /*   yes, end of string, so return */
2:      movs    r3, #0                  /* NUL */
        strb    r3, [r0]                /* write to end of string */
3:      ldrb    r3, [r1]                /* read a byte */
        adds    r1, r1, #1              /* advance to next byte */
        cmp     r3, #0                  /* was it a NUL? */
        bne     3b                      /*   no, get next byte */
4:      subs    r0, r1, r3              /* return length of src string */
        RET
END(strlcpy)
#elif defined(STRNCPY)
/* LINTSTUB: char * strncpy(char *, const char *, size_t) */
ENTRY(strncpy)
        mov     ip, r0                  /* we want to preserve r0 */
        adds    r2, r2, r0              /* get end of dst buffer */
        subs    r1, r1, r0              /* allows to only increment once */
1:      cmp     r0, r2                  /* are at the end of dst already? */
        beq     3f                      /*   yes, just return. */
        ldrb    r3, [r1, r0]            /* read a byte */
        strb    r3, [r0]                /* write a byte */
        adds    r0, r0, #1              /* advance a byte */
        cmp     r3, #0                  /* was it a NUL? */
        bne     1b                      /*   no, try next byte */
2:      cmp     r0, r2                  /* are at the end of dst already? */
        beq     3f                      /*   yes, exit loop
        strb    r3, [r0]                /* write a NUL */
        adds    r0, r0, #1              /* advance a bytes */
        b       2b                      /* until dst is filled */
3:      mov     r0, ip                  /* return dst pointer */
        RET
END(strncpy)
#else
/* LINTSTUB: char * strcpy(char *, const char *) */
ENTRY(strcpy)
        subs    r2, r0, r1              /* we want to preserve r0 */
1:      ldrb    r3, [r1]                /* read a byte */
        strb    r3, [r2, r1]            /* write a byte */
        adds    r1, r1, #1              /* advance to next byte */
        cmp     r3, #0                  /* was it a NUL? */
        bne     1b                      /*   no, try next byte */
        RET                             /* return dst pointer */
END(strcpy)
#endif