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Annotation of 43BSDReno/lib/libc/vax/string/memchr.s, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1990 The Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms are permitted
        !             6:  * provided that: (1) source distributions retain this entire copyright
        !             7:  * notice and comment, and (2) distributions including binaries display
        !             8:  * the following acknowledgement:  ``This product includes software
        !             9:  * developed by the University of California, Berkeley and its contributors''
        !            10:  * in the documentation or other materials provided with the distribution
        !            11:  * and in all advertising materials mentioning features or use of this
        !            12:  * software. Neither the name of the University nor the names of its
        !            13:  * contributors may be used to endorse or promote products derived
        !            14:  * from this software without specific prior written permission.
        !            15:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            16:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            17:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            18:  */
        !            19: 
        !            20: #if defined(LIBC_SCCS) && !defined(lint)
        !            21:        .asciz "@(#)memchr.s    5.1 (Berkeley) 5/29/90"
        !            22: #endif /* LIBC_SCCS and not lint */
        !            23: 
        !            24: /*
        !            25:  * Find the first occurence of c in the memory at cp (length n).
        !            26:  * Return pointer to match or null pointer.
        !            27:  *
        !            28:  * This code optimises the usual case (0 < n < 65535).
        !            29:  *
        !            30:  * void *
        !            31:  * memchr(cp, c, n)
        !            32:  *     char *cp, c;
        !            33:  *     size_t n;
        !            34:  */
        !            35: 
        !            36: #include "DEFS.h"
        !            37: 
        !            38: ENTRY(memchr, 0)
        !            39:        movq    4(ap),r1        # r1 = cp; r2 = c
        !            40:        movl    12(ap),r0       # r0 = n
        !            41:        movzwl  $65535,r4       # handy constant
        !            42: 0:
        !            43:        cmpl    r0,r4           # check for annoying locc limit
        !            44:        bgtru   3f
        !            45: 
        !            46:        /* n <= 65535 */
        !            47:        locc    r2,r0,(r1)      # search n bytes for c
        !            48:        beql    2f              # done if not found (r0 already 0)
        !            49: 1:     /* found character c at (r1) */
        !            50:        movl    r1,r0
        !            51: 2:
        !            52:        ret
        !            53: 
        !            54: 3:     /* n > 65535 */
        !            55:        locc    r2,r4,(r1)      # search 65535 bytes for c
        !            56:        beql    1b              # done if found
        !            57:        decw    r0              # from 0 to 65535
        !            58:        subl2   r0,r4           # adjust n
        !            59:        brb     0b              # and loop

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