/*- * See the file LICENSE for redistribution information. * * Copyright (c) 1996-2002 * Sleepycat Software. All rights reserved. */ /* * Copyright (c) 1990, 1993 * Margo Seltzer. All rights reserved. */ /* * Copyright (c) 1990, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Margo Seltzer. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include "db_config.h" #ifndef lint static const char revid[] = "$Id: hash_func.c,v 1.1.1.1 2003/02/15 04:56:06 zarzycki Exp $"; #endif /* not lint */ #ifndef NO_SYSTEM_INCLUDES #include <sys/types.h> #endif #include "db_int.h" /* * __ham_func2 -- * Phong Vo's linear congruential hash. * * PUBLIC: u_int32_t __ham_func2 __P((DB *, const void *, u_int32_t)); */ #define DCHARHASH(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c)) u_int32_t __ham_func2(dbp, key, len) DB *dbp; const void *key; u_int32_t len; { const u_int8_t *e, *k; u_int32_t h; u_int8_t c; if (dbp != NULL) COMPQUIET(dbp, NULL); k = key; e = k + len; for (h = 0; k != e;) { c = *k++; if (!c && k > e) break; DCHARHASH(h, c); } return (h); } /* * __ham_func3 -- * Ozan Yigit's original sdbm hash. * * Ugly, but fast. Break the string up into 8 byte units. On the first time * through the loop get the "leftover bytes" (strlen % 8). On every other * iteration, perform 8 HASHC's so we handle all 8 bytes. Essentially, this * saves us 7 cmp & branch instructions. * * PUBLIC: u_int32_t __ham_func3 __P((DB *, const void *, u_int32_t)); */ u_int32_t __ham_func3(dbp, key, len) DB *dbp; const void *key; u_int32_t len; { const u_int8_t *k; u_int32_t n, loop; if (dbp != NULL) COMPQUIET(dbp, NULL); if (len == 0) return (0); #define HASHC n = *k++ + 65599 * n n = 0; k = key; loop = (len + 8 - 1) >> 3; switch (len & (8 - 1)) { case 0: do { HASHC; case 7: HASHC; case 6: HASHC; case 5: HASHC; case 4: HASHC; case 3: HASHC; case 2: HASHC; case 1: HASHC; } while (--loop); } return (n); } /* * __ham_func4 -- * Chris Torek's hash function. Although this function performs only * slightly worse than __ham_func5 on strings, it performs horribly on * numbers. * * PUBLIC: u_int32_t __ham_func4 __P((DB *, const void *, u_int32_t)); */ u_int32_t __ham_func4(dbp, key, len) DB *dbp; const void *key; u_int32_t len; { const u_int8_t *k; u_int32_t h, loop; if (dbp != NULL) COMPQUIET(dbp, NULL); if (len == 0) return (0); #define HASH4a h = (h << 5) - h + *k++; #define HASH4b h = (h << 5) + h + *k++; #define HASH4 HASH4b h = 0; k = key; loop = (len + 8 - 1) >> 3; switch (len & (8 - 1)) { case 0: do { HASH4; case 7: HASH4; case 6: HASH4; case 5: HASH4; case 4: HASH4; case 3: HASH4; case 2: HASH4; case 1: HASH4; } while (--loop); } return (h); } /* * Fowler/Noll/Vo hash * * The basis of the hash algorithm was taken from an idea sent by email to the * IEEE Posix P1003.2 mailing list from Phong Vo (kpv@research.att.com) and * Glenn Fowler (gsf@research.att.com). Landon Curt Noll (chongo@toad.com) * later improved on their algorithm. * * The magic is in the interesting relationship between the special prime * 16777619 (2^24 + 403) and 2^32 and 2^8. * * This hash produces the fewest collisions of any function that we've seen so * far, and works well on both numbers and strings. * * PUBLIC: u_int32_t __ham_func5 __P((DB *, const void *, u_int32_t)); */ u_int32_t __ham_func5(dbp, key, len) DB *dbp; const void *key; u_int32_t len; { const u_int8_t *k, *e; u_int32_t h; if (dbp != NULL) COMPQUIET(dbp, NULL); k = key; e = k + len; for (h = 0; k < e; ++k) { h *= 16777619; h ^= *k; } return (h); } /* * __ham_test -- * * PUBLIC: u_int32_t __ham_test __P((DB *, const void *, u_int32_t)); */ u_int32_t __ham_test(dbp, key, len) DB *dbp; const void *key; u_int32_t len; { COMPQUIET(dbp, NULL); COMPQUIET(len, 0); return ((u_int32_t)*(char *)key); }