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Diffstat (limited to 'hashtable.c')
| -rw-r--r-- | hashtable.c | 303 |
1 files changed, 303 insertions, 0 deletions
diff --git a/hashtable.c b/hashtable.c new file mode 100644 index 0000000..68d34e8 --- /dev/null +++ b/hashtable.c @@ -0,0 +1,303 @@ +/* + Copyright (c) 2002, 2004, Christopher Clark + All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions are met: + + * Redistributions of source code must retain the above copyright notice, + this list of conditions and the following disclaimer. + + * 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. + + * Neither the name of the original author; nor the names of any + contributors may be used to endorse or promote products derived from this + software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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 "hashtable.h" +#include "hashtable_private.h" +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <math.h> + +/* +Credit for primes table: Aaron Krowne + http://br.endernet.org/~akrowne/ + http://planetmath.org/encyclopedia/GoodHashTablePrimes.html +*/ +static const unsigned int primes[] = { +53, 97, 193, 389, +769, 1543, 3079, 6151, +12289, 24593, 49157, 98317, +196613, 393241, 786433, 1572869, +3145739, 6291469, 12582917, 25165843, +50331653, 100663319, 201326611, 402653189, +805306457, 1610612741 +}; +const unsigned int prime_table_length = sizeof(primes)/sizeof(primes[0]); +const float max_load_factor = 0.65; + +/*****************************************************************************/ +struct hashtable * +create_hashtable(unsigned int minsize, + unsigned int (*hashf) (void*), + int (*eqf) (void*,void*)) +{ + struct hashtable *h; + unsigned int pindex, size = primes[0]; + /* Check requested hashtable isn't too large */ + if (minsize > (1u << 30)) return NULL; + /* Enforce size as prime */ + for (pindex=0; pindex < prime_table_length; pindex++) { + if (primes[pindex] > minsize) { size = primes[pindex]; break; } + } + h = (struct hashtable *)malloc(sizeof(struct hashtable)); + if (NULL == h) return NULL; /*oom*/ + h->table = (struct entry **)malloc(sizeof(struct entry*) * size); + if (NULL == h->table) { free(h); return NULL; } /*oom*/ + memset(h->table, 0, size * sizeof(struct entry *)); + h->tablelength = size; + h->primeindex = pindex; + h->entrycount = 0; + h->hashfn = hashf; + h->eqfn = eqf; + h->loadlimit = (unsigned int) ceil(size * max_load_factor); + return h; +} + +/*****************************************************************************/ +unsigned int +hash(struct hashtable *h, void *k) +{ + /* Aim to protect against poor hash functions by adding logic here + * - logic taken from java 1.4 hashtable source */ + unsigned int i = h->hashfn(k); + i += ~(i << 9); + i ^= ((i >> 14) | (i << 18)); /* >>> */ + i += (i << 4); + i ^= ((i >> 10) | (i << 22)); /* >>> */ + return i; +} + +/*****************************************************************************/ +static int +hashtable_expand(struct hashtable *h) +{ + /* Double the size of the table to accomodate more entries */ + struct entry **newtable; + struct entry *e; + struct entry **pE; + unsigned int newsize, i, index; + /* Check we're not hitting max capacity */ + if (h->primeindex == (prime_table_length - 1)) return 0; + newsize = primes[++(h->primeindex)]; + + newtable = (struct entry **)malloc(sizeof(struct entry*) * newsize); + if (NULL != newtable) + { + memset(newtable, 0, newsize * sizeof(struct entry *)); + /* This algorithm is not 'stable'. ie. it reverses the list + * when it transfers entries between the tables */ + for (i = 0; i < h->tablelength; i++) { + while (NULL != (e = h->table[i])) { + h->table[i] = e->next; + index = indexFor(newsize,e->h); + e->next = newtable[index]; + newtable[index] = e; + } + } + free(h->table); + h->table = newtable; + } + /* Plan B: realloc instead */ + else + { + newtable = (struct entry **) + realloc(h->table, newsize * sizeof(struct entry *)); + if (NULL == newtable) { (h->primeindex)--; return 0; } + h->table = newtable; + memset(newtable[h->tablelength], 0, newsize - h->tablelength); + for (i = 0; i < h->tablelength; i++) { + for (pE = &(newtable[i]), e = *pE; e != NULL; e = *pE) { + index = indexFor(newsize,e->h); + if (index == i) + { + pE = &(e->next); + } + else + { + *pE = e->next; + e->next = newtable[index]; + newtable[index] = e; + } + } + } + } + h->tablelength = newsize; + h->loadlimit = (unsigned int) ceil(newsize * max_load_factor); + return -1; +} + +/*****************************************************************************/ +unsigned int +hashtable_count(struct hashtable *h) +{ + return h->entrycount; +} + +/*****************************************************************************/ +int +hashtable_insert(struct hashtable *h, void *k, void *v) +{ + /* This method allows duplicate keys - but they shouldn't be used */ + unsigned int index; + struct entry *e; + if (++(h->entrycount) > h->loadlimit) + { + /* Ignore the return value. If expand fails, we should + * still try cramming just this value into the existing table + * -- we may not have memory for a larger table, but one more + * element may be ok. Next time we insert, we'll try expanding again.*/ + hashtable_expand(h); + } + e = (struct entry *)malloc(sizeof(struct entry)); + if (NULL == e) { --(h->entrycount); return 0; } /*oom*/ + e->h = hash(h,k); + index = indexFor(h->tablelength,e->h); + e->k = k; + e->v = v; + e->next = h->table[index]; + h->table[index] = e; + return -1; +} + +/*****************************************************************************/ +void * /* returns value associated with key */ +hashtable_search(struct hashtable *h, void *k) +{ + struct entry *e; + unsigned int hashvalue, index; + hashvalue = hash(h,k); + index = indexFor(h->tablelength,hashvalue); + e = h->table[index]; + while (NULL != e) + { + /* Check hash value to short circuit heavier comparison */ + if ((hashvalue == e->h) && (h->eqfn(k, e->k))) return e->v; + e = e->next; + } + return NULL; +} + +/*****************************************************************************/ +void * /* returns value associated with key */ +hashtable_remove(struct hashtable *h, void *k) +{ + /* TODO: consider compacting the table when the load factor drops enough, + * or provide a 'compact' method. */ + + struct entry *e; + struct entry **pE; + void *v; + unsigned int hashvalue, index; + + hashvalue = hash(h,k); + index = indexFor(h->tablelength,hash(h,k)); + pE = &(h->table[index]); + e = *pE; + while (NULL != e) + { + /* Check hash value to short circuit heavier comparison */ + if ((hashvalue == e->h) && (h->eqfn(k, e->k))) + { + *pE = e->next; + h->entrycount--; + v = e->v; + freekey(e->k); + free(e); + return v; + } + pE = &(e->next); + e = e->next; + } + return NULL; +} + +/*****************************************************************************/ +/* destroy */ +void +hashtable_destroy(struct hashtable *h, int free_values) +{ + unsigned int i; + struct entry *e, *f; + struct entry **table = h->table; + if (free_values) + { + for (i = 0; i < h->tablelength; i++) + { + e = table[i]; + while (NULL != e) + { f = e; e = e->next; freekey(f->k); free(f->v); free(f); } + } + } + else + { + for (i = 0; i < h->tablelength; i++) + { + e = table[i]; + while (NULL != e) + { f = e; e = e->next; freekey(f->k); free(f); } + } + } + free(h->table); + free(h); +} + +/* + * Copyright (c) 2002, Christopher Clark + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * 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. + * + * * Neither the name of the original author; nor the names of any contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER + * 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. +*/ |