/* Copyright (C) 2004 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */ #define PROGRAM_NAME "hashtable" #include "common.h" #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 = ARRAY_SIZE(primes); 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. */