The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/sys/hash.h

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    1 /*-
    2  * Copyright (c) 2001 Tobias Weingartner
    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  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   24  *
   25  * $OpenBSD: hash.h,v 1.4 2004/05/25 18:37:23 jmc Exp $
   26  * $FreeBSD$
   27  */
   28 
   29 #ifndef _SYS_HASH_H_
   30 #define _SYS_HASH_H_
   31 #include <sys/types.h>
   32 
   33 /* Convenience */
   34 #ifndef HASHINIT
   35 #define HASHINIT        5381
   36 #define HASHSTEP(x,c)   (((x << 5) + x) + (c))
   37 #endif
   38 
   39 /*
   40  * Return a 32-bit hash of the given buffer.  The init
   41  * value should be 0, or the previous hash value to extend
   42  * the previous hash.
   43  */
   44 static __inline uint32_t
   45 hash32_buf(const void *buf, size_t len, uint32_t hash)
   46 {
   47         const unsigned char *p = buf;
   48 
   49         while (len--)
   50                 hash = HASHSTEP(hash, *p++);
   51 
   52         return hash;
   53 }
   54 
   55 /*
   56  * Return a 32-bit hash of the given string.
   57  */
   58 static __inline uint32_t
   59 hash32_str(const void *buf, uint32_t hash)
   60 {
   61         const unsigned char *p = buf;
   62 
   63         while (*p)
   64                 hash = HASHSTEP(hash, *p++);
   65 
   66         return hash;
   67 }
   68 
   69 /*
   70  * Return a 32-bit hash of the given string, limited by N.
   71  */
   72 static __inline uint32_t
   73 hash32_strn(const void *buf, size_t len, uint32_t hash)
   74 {
   75         const unsigned char *p = buf;
   76 
   77         while (*p && len--)
   78                 hash = HASHSTEP(hash, *p++);
   79 
   80         return hash;
   81 }
   82 
   83 /*
   84  * Return a 32-bit hash of the given string terminated by C,
   85  * (as well as 0).  This is mainly here as a helper for the
   86  * namei() hashing of path name parts.
   87  */
   88 static __inline uint32_t
   89 hash32_stre(const void *buf, int end, const char **ep, uint32_t hash)
   90 {
   91         const unsigned char *p = buf;
   92 
   93         while (*p && (*p != end))
   94                 hash = HASHSTEP(hash, *p++);
   95 
   96         if (ep)
   97                 *ep = p;
   98 
   99         return hash;
  100 }
  101 
  102 /*
  103  * Return a 32-bit hash of the given string, limited by N,
  104  * and terminated by C (as well as 0).  This is mainly here
  105  * as a helper for the namei() hashing of path name parts.
  106  */
  107 static __inline uint32_t
  108 hash32_strne(const void *buf, size_t len, int end, const char **ep,
  109     uint32_t hash)
  110 {
  111         const unsigned char *p = buf;
  112 
  113         while (*p && (*p != end) && len--)
  114                 hash = HASHSTEP(hash, *p++);
  115 
  116         if (ep)
  117                 *ep = p;
  118 
  119         return hash;
  120 }
  121 #endif /* !_SYS_HASH_H_ */

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