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 /*      $OpenBSD: hash.h,v 1.4 2004/05/25 18:37:23 jmc Exp $    */
    2 
    3 /*
    4  * Copyright (c) 2001 Tobias Weingartner
    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 ``AS IS'' AND ANY EXPRESS OR
   17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   26  */
   27 
   28 #ifndef _SYS_HASH_H_
   29 #define _SYS_HASH_H_
   30 #include <sys/types.h>
   31 
   32 /*
   33  * Note: SMALL_KERNEL might be used to shrink these, right now I
   34  * do not see the point, as my kernel did not grow appreciably when
   35  * I switched to these from other inline code.  This may have to be
   36  * revisited when/if these functions become more prevalent in the
   37  * kernel.
   38  */
   39 
   40 /* Convenience */
   41 #ifndef HASHINIT
   42 #define HASHINIT        5381
   43 #define HASHSTEP(x,c)   (((x << 5) + x) + (c))
   44 #endif
   45 
   46 /*
   47  * Return a 32-bit hash of the given buffer.  The init
   48  * value should be 0, or the previous hash value to extend
   49  * the previous hash.
   50  */
   51 static __inline uint32_t
   52 hash32_buf(const void *buf, size_t len, uint32_t hash)
   53 {
   54         const unsigned char *p = buf;
   55 
   56         while (len--)
   57                 hash = HASHSTEP(hash, *p++);
   58 
   59         return hash;
   60 }
   61 
   62 /*
   63  * Return a 32-bit hash of the given string.
   64  */
   65 static __inline uint32_t
   66 hash32_str(const void *buf, uint32_t hash)
   67 {
   68         const unsigned char *p = buf;
   69 
   70         while (*p)
   71                 hash = HASHSTEP(hash, *p++);
   72 
   73         return hash;
   74 }
   75 
   76 /*
   77  * Return a 32-bit hash of the given string, limited by N.
   78  */
   79 static __inline uint32_t
   80 hash32_strn(const void *buf, size_t len, uint32_t hash)
   81 {
   82         const unsigned char *p = buf;
   83 
   84         while (*p && len--)
   85                 hash = HASHSTEP(hash, *p++);
   86 
   87         return hash;
   88 }
   89 
   90 /*
   91  * Return a 32-bit hash of the given string terminated by C,
   92  * (as well as 0).  This is mainly here as a helper for the
   93  * namei() hashing of path name parts.
   94  */
   95 static __inline uint32_t
   96 hash32_stre(const void *buf, int end, char **ep, uint32_t hash)
   97 {
   98         const unsigned char *p = buf;
   99 
  100         while (*p && (*p != end))
  101                 hash = HASHSTEP(hash, *p++);
  102 
  103         if (ep)
  104                 *ep = (char *)p;
  105 
  106         return hash;
  107 }
  108 
  109 /*
  110  * Return a 32-bit hash of the given string, limited by N,
  111  * and terminated by C (as well as 0).  This is mainly here
  112  * as a helper for the namei() hashing of path name parts.
  113  */
  114 static __inline uint32_t
  115 hash32_strne(const void *buf, size_t len, int end, char **ep, uint32_t hash)
  116 {
  117         const unsigned char *p = buf;
  118 
  119         while (*p && (*p != end) && len--)
  120                 hash = HASHSTEP(hash, *p++);
  121 
  122         if (ep)
  123                 *ep = (char *)p;
  124 
  125         return hash;
  126 }
  127 #endif /* !_SYS_HASH_H_ */

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