sysdeps/vax/strrchr.s

   1 /*
   2  * Copyright (c) 1988 Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #if defined(LIBC_SCCS) && !defined(lint)
  35         .asciz "@(#)strrchr.s   5.4 (Berkeley) 6/1/90"
  36 #endif /* LIBC_SCCS and not lint */
  37
  38 /*
  39  * Find the last occurrence of c in the string cp.
  40  * Return pointer to match or null pointer.
  41  *
  42  * char *
  43  * strrchr(cp, c)
  44  *      char *cp, c;
  45  */
  46 #include "DEFS.h"
  47
  48         .lcomm  tbl,256
  49
  50 ENTRY(strrchr, 0)
  51         movzwl  $65535,r4       /* handy 65535 */
  52         movq    4(ap),r1        /* r1 = cp; r2 = c */
  53         movzbl  r2,r2
  54         beql    Lzero           /* special case for c == '\0' */
  55
  56         clrl    r5              /* r5 = pointer to last match */
  57
  58 /*
  59  * Fancy scanc version.  Alas, it is not reentrant.
  60  */
  61         movab   tbl,r3          /* r3 = address of table */
  62         bbss    $0,(r3),Lreent  /* ensure not reentering */
  63         movab   (r3)[r2],r4
  64         incb    (r4)            /* mark both '\0' and c */
  65 0:
  66         scanc   $65535,(r1),(r3),$1     /* look for c or '\0' */
  67         beql    0b              /* keep looking */
  68         tstb    (r1)
  69         beql    1f              /* done if '\0' */
  70         movab   (r1)+,r5        /* save most recently found, and skip over it */
  71         jbr     0b              /* keep looking */
  72 1:
  73         movl    r5,r0           /* return last found (if any) */
  74         clrb    (r4)            /* clean up table */
  75         clrb    (r3)
  76         ret
  77
  78 /*
  79  * Special case for \0.
  80  */
  81 Lzero:
  82         locc    $0,r4,(r1)      /* just find end of string */
  83         beql    Lzero           /* still looking */
  84         movl    r1,r0           /* found it */
  85         ret
  86
  87 /*
  88  * Slower reentrant version is two two-step searches.  The first
  89  * phase runs until we know where the string ends; it locates any
  90  * occurrences of c within a 65535-byte block.  Once we have found
  91  * the end of the string, we find any further occurrences before
  92  * that location.
  93  */
  94 Lreent:
  95 0:      /* first phase */
  96         movl    r1,r3
  97         locc    $0,r4,(r3)      /* look for '\0' */
  98         bneq    1f
  99         locc    r2,r4,(r3)      /* continue phase 1 search for c */
 100         beql    0b
 101         movab   (r1)+,r5        /* found c: save and increment pointer */
 102         brb     0b              /* and continue */
 103
 104 1:      /* second phase */
 105         subl3   r3,r1,r0        /* length of short block */
 106         movl    r3,r1
 107 2:
 108         locc    r2,r0,(r1)      /* look for c */
 109         beql    3f              /* skip if not found */
 110         movab   (r1)+,r5        /* save pointer as before */
 111         sobgtr  r0,2b           /* adjust count and loop */
 112 3:
 113         movl    r5,r0           /* return stashed pointer */
 114         ret
 115
 116 weak_alias (strrchr, rindex)