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Annotation of 43BSDReno/lib/libc/vax/string/memchr.s, revision 1.1.1.1

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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