| /* 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. |
| */ |