strcspn.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2005 David Schultz <das@FreeBSD.ORG>
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD: releng/12.0/sys/libkern/strcspn.c 326271 2017-11-27 15:20:12Z pfg $");
   31 
   32 #include <sys/libkern.h>
   33 #include <sys/types.h>
   34 #include <sys/limits.h>
   35 
   36 #define IDX(c)  ((u_char)(c) / LONG_BIT)
   37 #define BIT(c)  ((u_long)1 << ((u_char)(c) % LONG_BIT))
   38 
   39 size_t 
   40 strcspn(const char * __restrict s, const char * __restrict charset) 
   41 {
   42         /*
   43          * NB: idx and bit are temporaries whose use causes gcc 3.4.2 to
   44          * generate better code.  Without them, gcc gets a little confused.
   45          */
   46         const char *s1;
   47         u_long bit;
   48         u_long tbl[(UCHAR_MAX + 1) / LONG_BIT];
   49         int idx;
   50 
   51         if(*s == '\0')
   52                 return (0);
   53 
   54 #if LONG_BIT == 64      /* always better to unroll on 64-bit architectures */
   55         tbl[0] = 1;
   56         tbl[3] = tbl[2] = tbl[1] = 0;
   57 #else
   58         for (tbl[0] = idx = 1; idx < sizeof(tbl) / sizeof(tbl[0]); idx++)
   59                 tbl[idx] = 0;
   60 #endif
   61         for (; *charset != '\0'; charset++) {
   62                 idx = IDX(*charset);
   63                 bit = BIT(*charset);
   64                 tbl[idx] |= bit;
   65         }
   66 
   67         for(s1 = s; ; s1++) {
   68                 idx = IDX(*s1);
   69                 bit = BIT(*s1);
   70                 if ((tbl[idx] & bit) != 0)
   71                         break;
   72         }
   73         return (s1 - s);
   74 }

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FreeBSD/Linux Kernel Cross Reference sys/libkern/strcspn.c

FreeBSD/Linux Kernel Cross Reference
sys/libkern/strcspn.c