usr/src/lib/libc/vax/string/memchr.s

/*-
 * Copyright (c) 1990 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
        .asciz "@(#)memchr.s    5.1 (Berkeley) 5/29/90"
#endif /* LIBC_SCCS and not lint */

/*
 * Find the first occurence of c in the memory at cp (length n).
 * Return pointer to match or null pointer.
 *
 * This code optimises the usual case (0 < n < 65535).
 *
 * void *
 * memchr(cp, c, n)
 *      char *cp, c;
 *      size_t n;
 */

#include "DEFS.h"

ENTRY(memchr, 0)
        movq    4(ap),r1        # r1 = cp; r2 = c
        movl    12(ap),r0       # r0 = n
        movzwl  $65535,r4       # handy constant
0:
        cmpl    r0,r4           # check for annoying locc limit
        bgtru   3f

        /* n <= 65535 */
        locc    r2,r0,(r1)      # search n bytes for c
        beql    2f              # done if not found (r0 already 0)
1:      /* found character c at (r1) */
        movl    r1,r0
2:
        ret

3:      /* n > 65535 */
        locc    r2,r4,(r1)      # search 65535 bytes for c
        beql    1b              # done if found
        decw    r0              # from 0 to 65535
        subl2   r0,r4           # adjust n
        brb     0b              # and loop