diff options
Diffstat (limited to 'gcc-4.7/libiberty/hashtab.c')
| -rw-r--r-- | gcc-4.7/libiberty/hashtab.c | 990 |
1 files changed, 0 insertions, 990 deletions
diff --git a/gcc-4.7/libiberty/hashtab.c b/gcc-4.7/libiberty/hashtab.c deleted file mode 100644 index dfaec0f31..000000000 --- a/gcc-4.7/libiberty/hashtab.c +++ /dev/null @@ -1,990 +0,0 @@ -/* An expandable hash tables datatype. - Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2009, 2010 - Free Software Foundation, Inc. - Contributed by Vladimir Makarov (vmakarov@cygnus.com). - -This file is part of the libiberty library. -Libiberty is free software; you can redistribute it and/or -modify it under the terms of the GNU Library General Public -License as published by the Free Software Foundation; either -version 2 of the License, or (at your option) any later version. - -Libiberty is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU -Library General Public License for more details. - -You should have received a copy of the GNU Library General Public -License along with libiberty; see the file COPYING.LIB. If -not, write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor, -Boston, MA 02110-1301, USA. */ - -/* This package implements basic hash table functionality. It is possible - to search for an entry, create an entry and destroy an entry. - - Elements in the table are generic pointers. - - The size of the table is not fixed; if the occupancy of the table - grows too high the hash table will be expanded. - - The abstract data implementation is based on generalized Algorithm D - from Knuth's book "The art of computer programming". Hash table is - expanded by creation of new hash table and transferring elements from - the old table to the new table. */ - -#ifdef HAVE_CONFIG_H -#include "config.h" -#endif - -#include <sys/types.h> - -#ifdef HAVE_STDLIB_H -#include <stdlib.h> -#endif -#ifdef HAVE_STRING_H -#include <string.h> -#endif -#ifdef HAVE_MALLOC_H -#include <malloc.h> -#endif -#ifdef HAVE_LIMITS_H -#include <limits.h> -#endif -#ifdef HAVE_INTTYPES_H -#include <inttypes.h> -#endif -#ifdef HAVE_STDINT_H -#include <stdint.h> -#endif - -#include <stdio.h> - -#include "libiberty.h" -#include "ansidecl.h" -#include "hashtab.h" - -#ifndef CHAR_BIT -#define CHAR_BIT 8 -#endif - -static unsigned int higher_prime_index (unsigned long); -static hashval_t htab_mod_1 (hashval_t, hashval_t, hashval_t, int); -static hashval_t htab_mod (hashval_t, htab_t); -static hashval_t htab_mod_m2 (hashval_t, htab_t); -static hashval_t hash_pointer (const void *); -static int eq_pointer (const void *, const void *); -static int htab_expand (htab_t); -static PTR *find_empty_slot_for_expand (htab_t, hashval_t); - -/* At some point, we could make these be NULL, and modify the - hash-table routines to handle NULL specially; that would avoid - function-call overhead for the common case of hashing pointers. */ -htab_hash htab_hash_pointer = hash_pointer; -htab_eq htab_eq_pointer = eq_pointer; - -/* Table of primes and multiplicative inverses. - - Note that these are not minimally reduced inverses. Unlike when generating - code to divide by a constant, we want to be able to use the same algorithm - all the time. All of these inverses (are implied to) have bit 32 set. - - For the record, here's the function that computed the table; it's a - vastly simplified version of the function of the same name from gcc. */ - -#if 0 -unsigned int -ceil_log2 (unsigned int x) -{ - int i; - for (i = 31; i >= 0 ; --i) - if (x > (1u << i)) - return i+1; - abort (); -} - -unsigned int -choose_multiplier (unsigned int d, unsigned int *mlp, unsigned char *shiftp) -{ - unsigned long long mhigh; - double nx; - int lgup, post_shift; - int pow, pow2; - int n = 32, precision = 32; - - lgup = ceil_log2 (d); - pow = n + lgup; - pow2 = n + lgup - precision; - - nx = ldexp (1.0, pow) + ldexp (1.0, pow2); - mhigh = nx / d; - - *shiftp = lgup - 1; - *mlp = mhigh; - return mhigh >> 32; -} -#endif - -struct prime_ent -{ - hashval_t prime; - hashval_t inv; - hashval_t inv_m2; /* inverse of prime-2 */ - hashval_t shift; -}; - -static struct prime_ent const prime_tab[] = { - { 7, 0x24924925, 0x9999999b, 2 }, - { 13, 0x3b13b13c, 0x745d1747, 3 }, - { 31, 0x08421085, 0x1a7b9612, 4 }, - { 61, 0x0c9714fc, 0x15b1e5f8, 5 }, - { 127, 0x02040811, 0x0624dd30, 6 }, - { 251, 0x05197f7e, 0x073260a5, 7 }, - { 509, 0x01824366, 0x02864fc8, 8 }, - { 1021, 0x00c0906d, 0x014191f7, 9 }, - { 2039, 0x0121456f, 0x0161e69e, 10 }, - { 4093, 0x00300902, 0x00501908, 11 }, - { 8191, 0x00080041, 0x00180241, 12 }, - { 16381, 0x000c0091, 0x00140191, 13 }, - { 32749, 0x002605a5, 0x002a06e6, 14 }, - { 65521, 0x000f00e2, 0x00110122, 15 }, - { 131071, 0x00008001, 0x00018003, 16 }, - { 262139, 0x00014002, 0x0001c004, 17 }, - { 524287, 0x00002001, 0x00006001, 18 }, - { 1048573, 0x00003001, 0x00005001, 19 }, - { 2097143, 0x00004801, 0x00005801, 20 }, - { 4194301, 0x00000c01, 0x00001401, 21 }, - { 8388593, 0x00001e01, 0x00002201, 22 }, - { 16777213, 0x00000301, 0x00000501, 23 }, - { 33554393, 0x00001381, 0x00001481, 24 }, - { 67108859, 0x00000141, 0x000001c1, 25 }, - { 134217689, 0x000004e1, 0x00000521, 26 }, - { 268435399, 0x00000391, 0x000003b1, 27 }, - { 536870909, 0x00000019, 0x00000029, 28 }, - { 1073741789, 0x0000008d, 0x00000095, 29 }, - { 2147483647, 0x00000003, 0x00000007, 30 }, - /* Avoid "decimal constant so large it is unsigned" for 4294967291. */ - { 0xfffffffb, 0x00000006, 0x00000008, 31 } -}; - -/* The following function returns an index into the above table of the - nearest prime number which is greater than N, and near a power of two. */ - -static unsigned int -higher_prime_index (unsigned long n) -{ - unsigned int low = 0; - unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]); - - while (low != high) - { - unsigned int mid = low + (high - low) / 2; - if (n > prime_tab[mid].prime) - low = mid + 1; - else - high = mid; - } - - /* If we've run out of primes, abort. */ - if (n > prime_tab[low].prime) - { - fprintf (stderr, "Cannot find prime bigger than %lu\n", n); - abort (); - } - - return low; -} - -/* Returns a hash code for P. */ - -static hashval_t -hash_pointer (const PTR p) -{ - return (hashval_t) ((intptr_t)p >> 3); -} - -/* Returns non-zero if P1 and P2 are equal. */ - -static int -eq_pointer (const PTR p1, const PTR p2) -{ - return p1 == p2; -} - - -/* The parens around the function names in the next two definitions - are essential in order to prevent macro expansions of the name. - The bodies, however, are expanded as expected, so they are not - recursive definitions. */ - -/* Return the current size of given hash table. */ - -#define htab_size(htab) ((htab)->size) - -size_t -(htab_size) (htab_t htab) -{ - return htab_size (htab); -} - -/* Return the current number of elements in given hash table. */ - -#define htab_elements(htab) ((htab)->n_elements - (htab)->n_deleted) - -size_t -(htab_elements) (htab_t htab) -{ - return htab_elements (htab); -} - -/* Return X % Y. */ - -static inline hashval_t -htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift) -{ - /* The multiplicative inverses computed above are for 32-bit types, and - requires that we be able to compute a highpart multiply. */ -#ifdef UNSIGNED_64BIT_TYPE - __extension__ typedef UNSIGNED_64BIT_TYPE ull; - if (sizeof (hashval_t) * CHAR_BIT <= 32) - { - hashval_t t1, t2, t3, t4, q, r; - - t1 = ((ull)x * inv) >> 32; - t2 = x - t1; - t3 = t2 >> 1; - t4 = t1 + t3; - q = t4 >> shift; - r = x - (q * y); - - return r; - } -#endif - - /* Otherwise just use the native division routines. */ - return x % y; -} - -/* Compute the primary hash for HASH given HTAB's current size. */ - -static inline hashval_t -htab_mod (hashval_t hash, htab_t htab) -{ - const struct prime_ent *p = &prime_tab[htab->size_prime_index]; - return htab_mod_1 (hash, p->prime, p->inv, p->shift); -} - -/* Compute the secondary hash for HASH given HTAB's current size. */ - -static inline hashval_t -htab_mod_m2 (hashval_t hash, htab_t htab) -{ - const struct prime_ent *p = &prime_tab[htab->size_prime_index]; - return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift); -} - -/* This function creates table with length slightly longer than given - source length. Created hash table is initiated as empty (all the - hash table entries are HTAB_EMPTY_ENTRY). The function returns the - created hash table, or NULL if memory allocation fails. */ - -htab_t -htab_create_alloc (size_t size, htab_hash hash_f, htab_eq eq_f, - htab_del del_f, htab_alloc alloc_f, htab_free free_f) -{ - return htab_create_typed_alloc (size, hash_f, eq_f, del_f, alloc_f, alloc_f, - free_f); -} - -/* As above, but uses the variants of ALLOC_F and FREE_F which accept - an extra argument. */ - -htab_t -htab_create_alloc_ex (size_t size, htab_hash hash_f, htab_eq eq_f, - htab_del del_f, void *alloc_arg, - htab_alloc_with_arg alloc_f, - htab_free_with_arg free_f) -{ - htab_t result; - unsigned int size_prime_index; - - size_prime_index = higher_prime_index (size); - size = prime_tab[size_prime_index].prime; - - result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab)); - if (result == NULL) - return NULL; - result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR)); - if (result->entries == NULL) - { - if (free_f != NULL) - (*free_f) (alloc_arg, result); - return NULL; - } - result->size = size; - result->size_prime_index = size_prime_index; - result->hash_f = hash_f; - result->eq_f = eq_f; - result->del_f = del_f; - result->alloc_arg = alloc_arg; - result->alloc_with_arg_f = alloc_f; - result->free_with_arg_f = free_f; - return result; -} - -/* - -@deftypefn Supplemental htab_t htab_create_typed_alloc (size_t @var{size}, @ -htab_hash @var{hash_f}, htab_eq @var{eq_f}, htab_del @var{del_f}, @ -htab_alloc @var{alloc_tab_f}, htab_alloc @var{alloc_f}, @ -htab_free @var{free_f}) - -This function creates a hash table that uses two different allocators -@var{alloc_tab_f} and @var{alloc_f} to use for allocating the table itself -and its entries respectively. This is useful when variables of different -types need to be allocated with different allocators. - -The created hash table is slightly larger than @var{size} and it is -initially empty (all the hash table entries are @code{HTAB_EMPTY_ENTRY}). -The function returns the created hash table, or @code{NULL} if memory -allocation fails. - -@end deftypefn - -*/ - -htab_t -htab_create_typed_alloc (size_t size, htab_hash hash_f, htab_eq eq_f, - htab_del del_f, htab_alloc alloc_tab_f, - htab_alloc alloc_f, htab_free free_f) -{ - htab_t result; - unsigned int size_prime_index; - - size_prime_index = higher_prime_index (size); - size = prime_tab[size_prime_index].prime; - - result = (htab_t) (*alloc_tab_f) (1, sizeof (struct htab)); - if (result == NULL) - return NULL; - result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR)); - if (result->entries == NULL) - { - if (free_f != NULL) - (*free_f) (result); - return NULL; - } - result->size = size; - result->size_prime_index = size_prime_index; - result->hash_f = hash_f; - result->eq_f = eq_f; - result->del_f = del_f; - result->alloc_f = alloc_f; - result->free_f = free_f; - return result; -} - - -/* Update the function pointers and allocation parameter in the htab_t. */ - -void -htab_set_functions_ex (htab_t htab, htab_hash hash_f, htab_eq eq_f, - htab_del del_f, PTR alloc_arg, - htab_alloc_with_arg alloc_f, htab_free_with_arg free_f) -{ - htab->hash_f = hash_f; - htab->eq_f = eq_f; - htab->del_f = del_f; - htab->alloc_arg = alloc_arg; - htab->alloc_with_arg_f = alloc_f; - htab->free_with_arg_f = free_f; -} - -/* These functions exist solely for backward compatibility. */ - -#undef htab_create -htab_t -htab_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f) -{ - return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free); -} - -htab_t -htab_try_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f) -{ - return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free); -} - -/* This function frees all memory allocated for given hash table. - Naturally the hash table must already exist. */ - -void -htab_delete (htab_t htab) -{ - size_t size = htab_size (htab); - PTR *entries = htab->entries; - int i; - - if (htab->del_f) - for (i = size - 1; i >= 0; i--) - if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY) - (*htab->del_f) (entries[i]); - - if (htab->free_f != NULL) - { - (*htab->free_f) (entries); - (*htab->free_f) (htab); - } - else if (htab->free_with_arg_f != NULL) - { - (*htab->free_with_arg_f) (htab->alloc_arg, entries); - (*htab->free_with_arg_f) (htab->alloc_arg, htab); - } -} - -/* This function clears all entries in the given hash table. */ - -void -htab_empty (htab_t htab) -{ - size_t size = htab_size (htab); - PTR *entries = htab->entries; - int i; - - if (htab->del_f) - for (i = size - 1; i >= 0; i--) - if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY) - (*htab->del_f) (entries[i]); - - /* Instead of clearing megabyte, downsize the table. */ - if (size > 1024*1024 / sizeof (PTR)) - { - int nindex = higher_prime_index (1024 / sizeof (PTR)); - int nsize = prime_tab[nindex].prime; - - if (htab->free_f != NULL) - (*htab->free_f) (htab->entries); - else if (htab->free_with_arg_f != NULL) - (*htab->free_with_arg_f) (htab->alloc_arg, htab->entries); - if (htab->alloc_with_arg_f != NULL) - htab->entries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize, - sizeof (PTR *)); - else - htab->entries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *)); - htab->size = nsize; - htab->size_prime_index = nindex; - } - else - memset (entries, 0, size * sizeof (PTR)); - htab->n_deleted = 0; - htab->n_elements = 0; -} - -/* Similar to htab_find_slot, but without several unwanted side effects: - - Does not call htab->eq_f when it finds an existing entry. - - Does not change the count of elements/searches/collisions in the - hash table. - This function also assumes there are no deleted entries in the table. - HASH is the hash value for the element to be inserted. */ - -static PTR * -find_empty_slot_for_expand (htab_t htab, hashval_t hash) -{ - hashval_t index = htab_mod (hash, htab); - size_t size = htab_size (htab); - PTR *slot = htab->entries + index; - hashval_t hash2; - - if (*slot == HTAB_EMPTY_ENTRY) - return slot; - else if (*slot == HTAB_DELETED_ENTRY) - abort (); - - hash2 = htab_mod_m2 (hash, htab); - for (;;) - { - index += hash2; - if (index >= size) - index -= size; - - slot = htab->entries + index; - if (*slot == HTAB_EMPTY_ENTRY) - return slot; - else if (*slot == HTAB_DELETED_ENTRY) - abort (); - } -} - -/* The following function changes size of memory allocated for the - entries and repeatedly inserts the table elements. The occupancy - of the table after the call will be about 50%. Naturally the hash - table must already exist. Remember also that the place of the - table entries is changed. If memory allocation failures are allowed, - this function will return zero, indicating that the table could not be - expanded. If all goes well, it will return a non-zero value. */ - -static int -htab_expand (htab_t htab) -{ - PTR *oentries; - PTR *olimit; - PTR *p; - PTR *nentries; - size_t nsize, osize, elts; - unsigned int oindex, nindex; - - oentries = htab->entries; - oindex = htab->size_prime_index; - osize = htab->size; - olimit = oentries + osize; - elts = htab_elements (htab); - - /* Resize only when table after removal of unused elements is either - too full or too empty. */ - if (elts * 2 > osize || (elts * 8 < osize && osize > 32)) - { - nindex = higher_prime_index (elts * 2); - nsize = prime_tab[nindex].prime; - } - else - { - nindex = oindex; - nsize = osize; - } - - if (htab->alloc_with_arg_f != NULL) - nentries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize, - sizeof (PTR *)); - else - nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *)); - if (nentries == NULL) - return 0; - htab->entries = nentries; - htab->size = nsize; - htab->size_prime_index = nindex; - htab->n_elements -= htab->n_deleted; - htab->n_deleted = 0; - - p = oentries; - do - { - PTR x = *p; - - if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY) - { - PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x)); - - *q = x; - } - - p++; - } - while (p < olimit); - - if (htab->free_f != NULL) - (*htab->free_f) (oentries); - else if (htab->free_with_arg_f != NULL) - (*htab->free_with_arg_f) (htab->alloc_arg, oentries); - return 1; -} - -/* This function searches for a hash table entry equal to the given - element. It cannot be used to insert or delete an element. */ - -PTR -htab_find_with_hash (htab_t htab, const PTR element, hashval_t hash) -{ - hashval_t index, hash2; - size_t size; - PTR entry; - - htab->searches++; - size = htab_size (htab); - index = htab_mod (hash, htab); - - entry = htab->entries[index]; - if (entry == HTAB_EMPTY_ENTRY - || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element))) - return entry; - - hash2 = htab_mod_m2 (hash, htab); - for (;;) - { - htab->collisions++; - index += hash2; - if (index >= size) - index -= size; - - entry = htab->entries[index]; - if (entry == HTAB_EMPTY_ENTRY - || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element))) - return entry; - } -} - -/* Like htab_find_slot_with_hash, but compute the hash value from the - element. */ - -PTR -htab_find (htab_t htab, const PTR element) -{ - return htab_find_with_hash (htab, element, (*htab->hash_f) (element)); -} - -/* This function searches for a hash table slot containing an entry - equal to the given element. To delete an entry, call this with - insert=NO_INSERT, then call htab_clear_slot on the slot returned - (possibly after doing some checks). To insert an entry, call this - with insert=INSERT, then write the value you want into the returned - slot. When inserting an entry, NULL may be returned if memory - allocation fails. */ - -PTR * -htab_find_slot_with_hash (htab_t htab, const PTR element, - hashval_t hash, enum insert_option insert) -{ - PTR *first_deleted_slot; - hashval_t index, hash2; - size_t size; - PTR entry; - - size = htab_size (htab); - if (insert == INSERT && size * 3 <= htab->n_elements * 4) - { - if (htab_expand (htab) == 0) - return NULL; - size = htab_size (htab); - } - - index = htab_mod (hash, htab); - - htab->searches++; - first_deleted_slot = NULL; - - entry = htab->entries[index]; - if (entry == HTAB_EMPTY_ENTRY) - goto empty_entry; - else if (entry == HTAB_DELETED_ENTRY) - first_deleted_slot = &htab->entries[index]; - else if ((*htab->eq_f) (entry, element)) - return &htab->entries[index]; - - hash2 = htab_mod_m2 (hash, htab); - for (;;) - { - htab->collisions++; - index += hash2; - if (index >= size) - index -= size; - - entry = htab->entries[index]; - if (entry == HTAB_EMPTY_ENTRY) - goto empty_entry; - else if (entry == HTAB_DELETED_ENTRY) - { - if (!first_deleted_slot) - first_deleted_slot = &htab->entries[index]; - } - else if ((*htab->eq_f) (entry, element)) - return &htab->entries[index]; - } - - empty_entry: - if (insert == NO_INSERT) - return NULL; - - if (first_deleted_slot) - { - htab->n_deleted--; - *first_deleted_slot = HTAB_EMPTY_ENTRY; - return first_deleted_slot; - } - - htab->n_elements++; - return &htab->entries[index]; -} - -/* Like htab_find_slot_with_hash, but compute the hash value from the - element. */ - -PTR * -htab_find_slot (htab_t htab, const PTR element, enum insert_option insert) -{ - return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element), - insert); -} - -/* This function deletes an element with the given value from hash - table (the hash is computed from the element). If there is no matching - element in the hash table, this function does nothing. */ - -void -htab_remove_elt (htab_t htab, PTR element) -{ - htab_remove_elt_with_hash (htab, element, (*htab->hash_f) (element)); -} - - -/* This function deletes an element with the given value from hash - table. If there is no matching element in the hash table, this - function does nothing. */ - -void -htab_remove_elt_with_hash (htab_t htab, PTR element, hashval_t hash) -{ - PTR *slot; - - slot = htab_find_slot_with_hash (htab, element, hash, NO_INSERT); - if (*slot == HTAB_EMPTY_ENTRY) - return; - - if (htab->del_f) - (*htab->del_f) (*slot); - - *slot = HTAB_DELETED_ENTRY; - htab->n_deleted++; -} - -/* This function clears a specified slot in a hash table. It is - useful when you've already done the lookup and don't want to do it - again. */ - -void -htab_clear_slot (htab_t htab, PTR *slot) -{ - if (slot < htab->entries || slot >= htab->entries + htab_size (htab) - || *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY) - abort (); - - if (htab->del_f) - (*htab->del_f) (*slot); - - *slot = HTAB_DELETED_ENTRY; - htab->n_deleted++; -} - -/* This function scans over the entire hash table calling - CALLBACK for each live entry. If CALLBACK returns false, - the iteration stops. INFO is passed as CALLBACK's second - argument. */ - -void -htab_traverse_noresize (htab_t htab, htab_trav callback, PTR info) -{ - PTR *slot; - PTR *limit; - - slot = htab->entries; - limit = slot + htab_size (htab); - - do - { - PTR x = *slot; - - if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY) - if (!(*callback) (slot, info)) - break; - } - while (++slot < limit); -} - -/* Like htab_traverse_noresize, but does resize the table when it is - too empty to improve effectivity of subsequent calls. */ - -void -htab_traverse (htab_t htab, htab_trav callback, PTR info) -{ - size_t size = htab_size (htab); - if (htab_elements (htab) * 8 < size && size > 32) - htab_expand (htab); - - htab_traverse_noresize (htab, callback, info); -} - -/* Return the fraction of fixed collisions during all work with given - hash table. */ - -double -htab_collisions (htab_t htab) -{ - if (htab->searches == 0) - return 0.0; - - return (double) htab->collisions / (double) htab->searches; -} - -/* Hash P as a null-terminated string. - - Copied from gcc/hashtable.c. Zack had the following to say with respect - to applicability, though note that unlike hashtable.c, this hash table - implementation re-hashes rather than chain buckets. - - http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html - From: Zack Weinberg <zackw@panix.com> - Date: Fri, 17 Aug 2001 02:15:56 -0400 - - I got it by extracting all the identifiers from all the source code - I had lying around in mid-1999, and testing many recurrences of - the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either - prime numbers or the appropriate identity. This was the best one. - I don't remember exactly what constituted "best", except I was - looking at bucket-length distributions mostly. - - So it should be very good at hashing identifiers, but might not be - as good at arbitrary strings. - - I'll add that it thoroughly trounces the hash functions recommended - for this use at http://burtleburtle.net/bob/hash/index.html, both - on speed and bucket distribution. I haven't tried it against the - function they just started using for Perl's hashes. */ - -hashval_t -htab_hash_string (const PTR p) -{ - const unsigned char *str = (const unsigned char *) p; - hashval_t r = 0; - unsigned char c; - - while ((c = *str++) != 0) - r = r * 67 + c - 113; - - return r; -} - -/* DERIVED FROM: --------------------------------------------------------------------- -lookup2.c, by Bob Jenkins, December 1996, Public Domain. -hash(), hash2(), hash3, and mix() are externally useful functions. -Routines to test the hash are included if SELF_TEST is defined. -You can use this free for any purpose. It has no warranty. --------------------------------------------------------------------- -*/ - -/* --------------------------------------------------------------------- -mix -- mix 3 32-bit values reversibly. -For every delta with one or two bit set, and the deltas of all three - high bits or all three low bits, whether the original value of a,b,c - is almost all zero or is uniformly distributed, -* If mix() is run forward or backward, at least 32 bits in a,b,c - have at least 1/4 probability of changing. -* If mix() is run forward, every bit of c will change between 1/3 and - 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.) -mix() was built out of 36 single-cycle latency instructions in a - structure that could supported 2x parallelism, like so: - a -= b; - a -= c; x = (c>>13); - b -= c; a ^= x; - b -= a; x = (a<<8); - c -= a; b ^= x; - c -= b; x = (b>>13); - ... - Unfortunately, superscalar Pentiums and Sparcs can't take advantage - of that parallelism. They've also turned some of those single-cycle - latency instructions into multi-cycle latency instructions. Still, - this is the fastest good hash I could find. There were about 2^^68 - to choose from. I only looked at a billion or so. --------------------------------------------------------------------- -*/ -/* same, but slower, works on systems that might have 8 byte hashval_t's */ -#define mix(a,b,c) \ -{ \ - a -= b; a -= c; a ^= (c>>13); \ - b -= c; b -= a; b ^= (a<< 8); \ - c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \ - a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \ - b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \ - c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \ - a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \ - b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \ - c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \ -} - -/* --------------------------------------------------------------------- -hash() -- hash a variable-length key into a 32-bit value - k : the key (the unaligned variable-length array of bytes) - len : the length of the key, counting by bytes - level : can be any 4-byte value -Returns a 32-bit value. Every bit of the key affects every bit of -the return value. Every 1-bit and 2-bit delta achieves avalanche. -About 36+6len instructions. - -The best hash table sizes are powers of 2. There is no need to do -mod a prime (mod is sooo slow!). If you need less than 32 bits, -use a bitmask. For example, if you need only 10 bits, do - h = (h & hashmask(10)); -In which case, the hash table should have hashsize(10) elements. - -If you are hashing n strings (ub1 **)k, do it like this: - for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h); - -By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this -code any way you wish, private, educational, or commercial. It's free. - -See http://burtleburtle.net/bob/hash/evahash.html -Use for hash table lookup, or anything where one collision in 2^32 is -acceptable. Do NOT use for cryptographic purposes. --------------------------------------------------------------------- -*/ - -hashval_t -iterative_hash (const PTR k_in /* the key */, - register size_t length /* the length of the key */, - register hashval_t initval /* the previous hash, or - an arbitrary value */) -{ - register const unsigned char *k = (const unsigned char *)k_in; - register hashval_t a,b,c,len; - - /* Set up the internal state */ - len = length; - a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */ - c = initval; /* the previous hash value */ - - /*---------------------------------------- handle most of the key */ -#ifndef WORDS_BIGENDIAN - /* On a little-endian machine, if the data is 4-byte aligned we can hash - by word for better speed. This gives nondeterministic results on - big-endian machines. */ - if (sizeof (hashval_t) == 4 && (((size_t)k)&3) == 0) - while (len >= 12) /* aligned */ - { - a += *(hashval_t *)(k+0); - b += *(hashval_t *)(k+4); - c += *(hashval_t *)(k+8); - mix(a,b,c); - k += 12; len -= 12; - } - else /* unaligned */ -#endif - while (len >= 12) - { - a += (k[0] +((hashval_t)k[1]<<8) +((hashval_t)k[2]<<16) +((hashval_t)k[3]<<24)); - b += (k[4] +((hashval_t)k[5]<<8) +((hashval_t)k[6]<<16) +((hashval_t)k[7]<<24)); - c += (k[8] +((hashval_t)k[9]<<8) +((hashval_t)k[10]<<16)+((hashval_t)k[11]<<24)); - mix(a,b,c); - k += 12; len -= 12; - } - - /*------------------------------------- handle the last 11 bytes */ - c += length; - switch(len) /* all the case statements fall through */ - { - case 11: c+=((hashval_t)k[10]<<24); - case 10: c+=((hashval_t)k[9]<<16); - case 9 : c+=((hashval_t)k[8]<<8); - /* the first byte of c is reserved for the length */ - case 8 : b+=((hashval_t)k[7]<<24); - case 7 : b+=((hashval_t)k[6]<<16); - case 6 : b+=((hashval_t)k[5]<<8); - case 5 : b+=k[4]; - case 4 : a+=((hashval_t)k[3]<<24); - case 3 : a+=((hashval_t)k[2]<<16); - case 2 : a+=((hashval_t)k[1]<<8); - case 1 : a+=k[0]; - /* case 0: nothing left to add */ - } - mix(a,b,c); - /*-------------------------------------------- report the result */ - return c; -} |