sysdeps/vax/strchr.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  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #if defined(LIBC_SCCS) && !defined(lint)
  31         .asciz "@(#)strchr.s    5.4 (Berkeley) 6/1/90"
  32 #endif /* LIBC_SCCS and not lint */
  33
  34 /*
  35  * Find the first occurrence of c in the string cp.
  36  * Return pointer to match or null pointer.
  37  *
  38  * char *
  39  * strchr(cp, c)
  40  *      char *cp, c;
  41  */
  42 #include "DEFS.h"
  43
  44         .lcomm  tbl,256
  45
  46 ENTRY(strchr, 0)
  47         movzwl  $65535,r4       /* handy constant */
  48         movq    4(ap),r1        /* r1 = cp; r2 = c */
  49         movzbl  r2,r2
  50         beql    Lzero           /* special case for c == '\0' */
  51
  52 /*
  53  * Fancy scanc version.  Alas, it is not reentrant.
  54  */
  55         movab   tbl,r3          /* r3 = base of table */
  56         bbss    $0,(r3),Lreent  /* ensure not reentering */
  57         movab   (r3)[r2],r5
  58         incb    (r5)            /* mark both '\0' and c */
  59 0:
  60         scanc   r4,(r1),(r3),$1 /* look for c or '\0' */
  61         beql    0b              /* still looking */
  62         movl    r1,r0           /* return whatever we found */
  63         tstb    (r0)
  64         bneq    1f              #       unless it was '\0':
  65         clrl    r0              #       then return NULL
  66 1:
  67         clrb    (r5)            /* clean up table */
  68         clrb    (r3)
  69         ret
  70
  71 /*
  72  * Special case for \0.
  73  */
  74 Lzero:
  75         locc    r2,r4,(r1)      /* just find end of string */
  76         beql    Lzero           /* still looking */
  77         movl    r1,r0           /* found it */
  78         ret
  79
  80 /*
  81  * Slower reentrant version is two two-step searches.  The first
  82  * phase runs until we know where the string ends; it locates the
  83  * first occurrence of c within a 65535-byte block.  If we find
  84  * the end of the string first, we switch to the second phase,
  85  * were we look only up to the known end of string.
  86  */
  87 Lreent:
  88 0:      /* first phase */
  89         movl    r1,r3
  90         locc    $0,r4,(r3)      /* look for '\0' */
  91         bneq    1f
  92         locc    r2,r4,(r3)      /* look for c */
  93         beql    0b              /* not found: reset pointer and loop */
  94         movl    r1,r0           /* found: return it */
  95         ret
  96 1:      /* second phase */
  97         subl3   r3,r1,r0        /* length of short block */
  98         locc    r2,r0,(r3)      /* look for c */
  99         beql    2f              /* not found: return NULL */
 100         movl    r1,r0
 101 2:      ret
 102
 103 weak_alias (strchr, index)