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/* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
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* Copyright (C) 2011-2012 Data Differential, http://datadifferential.com/
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* Copyright (C) 2006-2009 Brian Aker All rights reserved.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* * The names of its contributors may not be used to endorse or
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* promote products derived from this software without specific prior
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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* By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this
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* code any way you wish, private, educational, or commercial. It's free.
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* Use for hash table lookup, or anything where one collision in 2^^32 is
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* acceptable. Do NOT use for cryptographic purposes.
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* http://burtleburtle.net/bob/hash/index.html
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* Modified by Brian Pontz for libmemcached
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* Add big endian support
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#include <libhashkit/common.h>
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#define hashsize(n) ((uint32_t)1<<(n))
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#define hashmask(n) (hashsize(n)-1)
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#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
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a -= c; a ^= rot(c, 4); c += b; \
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b -= a; b ^= rot(a, 6); a += c; \
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c -= b; c ^= rot(b, 8); b += a; \
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a -= c; a ^= rot(c,16); c += b; \
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b -= a; b ^= rot(a,19); a += c; \
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c -= b; c ^= rot(b, 4); b += a; \
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#define final(a,b,c) \
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c ^= b; c -= rot(b,14); \
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a ^= c; a -= rot(c,11); \
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b ^= a; b -= rot(a,25); \
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c ^= b; c -= rot(b,16); \
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a ^= c; a -= rot(c,4); \
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b ^= a; b -= rot(a,14); \
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c ^= b; c -= rot(b,24); \
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#define JENKINS_INITVAL 13
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jenkins_hash() -- hash a variable-length key into a 32-bit value
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k : the key (the unaligned variable-length array of bytes)
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length : the length of the key, counting by bytes
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initval : can be any 4-byte value
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Returns a 32-bit value. Every bit of the key affects every bit of
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the return value. Two keys differing by one or two bits will have
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totally different hash values.
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The best hash table sizes are powers of 2. There is no need to do
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mod a prime (mod is sooo slow!). If you need less than 32 bits,
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use a bitmask. For example, if you need only 10 bits, do
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h = (h & hashmask(10));
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In which case, the hash table should have hashsize(10) elements.
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uint32_t hashkit_jenkins(const char *key, size_t length, void *)
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uint32_t a,b,c; /* internal state */
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#ifndef WORDS_BIGENDIAN
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union { const void *ptr; size_t i; } u;
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/* Set up the internal state */
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a = b = c = 0xdeadbeef + ((uint32_t)length) + JENKINS_INITVAL;
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#ifndef WORDS_BIGENDIAN
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if ((u.i & 0x3) == 0)
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const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
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/*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
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/*----------------------------- handle the last (probably partial) block */
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* "k[2]&0xffffff" actually reads beyond the end of the string, but
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* then masks off the part it's not allowed to read. Because the
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* string is aligned, the masked-off tail is in the same word as the
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* rest of the string. Every machine with memory protection I've seen
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* does it on word boundaries, so is OK with this. But VALGRIND will
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* still catch it and complain. The masking trick does make the hash
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* noticably faster for short strings (like English words).
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case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
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case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
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case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
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case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
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case 8 : b+=k[1]; a+=k[0]; break;
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case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
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case 6 : b+=k[1]&0xffff; a+=k[0]; break;
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case 5 : b+=k[1]&0xff; a+=k[0]; break;
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case 4 : a+=k[0]; break;
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case 3 : a+=k[0]&0xffffff; break;
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case 2 : a+=k[0]&0xffff; break;
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case 1 : a+=k[0]&0xff; break;
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case 0 : return c; /* zero length strings require no mixing */
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else if ((u.i & 0x1) == 0)
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const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */
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/*--------------- all but last block: aligned reads and different mixing */
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a += k[0] + (((uint32_t)k[1])<<16);
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b += k[2] + (((uint32_t)k[3])<<16);
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c += k[4] + (((uint32_t)k[5])<<16);
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/*----------------------------- handle the last (probably partial) block */
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k8 = (const uint8_t *)k;
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case 12: c+=k[4]+(((uint32_t)k[5])<<16);
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b+=k[2]+(((uint32_t)k[3])<<16);
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a+=k[0]+(((uint32_t)k[1])<<16);
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case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
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b+=k[2]+(((uint32_t)k[3])<<16);
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a+=k[0]+(((uint32_t)k[1])<<16);
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case 9 : c+=k8[8]; /* fall through */
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case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
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a+=k[0]+(((uint32_t)k[1])<<16);
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case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
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a+=k[0]+(((uint32_t)k[1])<<16);
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case 5 : b+=k8[4]; /* fall through */
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case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
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case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
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case 0 : return c; /* zero length requires no mixing */
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{ /* need to read the key one byte at a time */
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#endif /* little endian */
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const uint8_t *k = (const uint8_t *)key;
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/*--------------- all but the last block: affect some 32 bits of (a,b,c) */
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a += ((uint32_t)k[1])<<8;
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a += ((uint32_t)k[2])<<16;
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a += ((uint32_t)k[3])<<24;
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b += ((uint32_t)k[5])<<8;
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b += ((uint32_t)k[6])<<16;
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b += ((uint32_t)k[7])<<24;
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c += ((uint32_t)k[9])<<8;
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c += ((uint32_t)k[10])<<16;
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c += ((uint32_t)k[11])<<24;
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/*-------------------------------- last block: affect all 32 bits of (c) */
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switch(length) /* all the case statements fall through */
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case 12: c+=((uint32_t)k[11])<<24;
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case 11: c+=((uint32_t)k[10])<<16;
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case 10: c+=((uint32_t)k[9])<<8;
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case 8 : b+=((uint32_t)k[7])<<24;
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case 7 : b+=((uint32_t)k[6])<<16;
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case 6 : b+=((uint32_t)k[5])<<8;
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case 4 : a+=((uint32_t)k[3])<<24;
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case 3 : a+=((uint32_t)k[2])<<16;
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case 2 : a+=((uint32_t)k[1])<<8;
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#ifndef WORDS_BIGENDIAN
added
removed
libhashkit/jenkins.cc
