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Annotation of sys/sys/hash.h, Revision 1.1

1.1     ! nbrk        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_ */