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This commit is contained in:
Anthony Minessale
274
libs/freetdm/src/hashtable.c
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274
libs/freetdm/src/hashtable.c
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/* Copyright (C) 2004 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */
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#include "hashtable.h"
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#include "hashtable_private.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <math.h>
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/*
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Credit for primes table: Aaron Krowne
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http://br.endernet.org/~akrowne/
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http://planetmath.org/encyclopedia/GoodHashTablePrimes.html
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*/
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static const unsigned int primes[] = {
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53, 97, 193, 389,
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769, 1543, 3079, 6151,
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12289, 24593, 49157, 98317,
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196613, 393241, 786433, 1572869,
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3145739, 6291469, 12582917, 25165843,
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50331653, 100663319, 201326611, 402653189,
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805306457, 1610612741
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};
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const unsigned int prime_table_length = sizeof(primes)/sizeof(primes[0]);
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const float max_load_factor = 0.65;
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/*****************************************************************************/
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struct hashtable *
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create_hashtable(unsigned int minsize,
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unsigned int (*hashf) (void*),
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int (*eqf) (void*,void*))
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{
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struct hashtable *h;
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unsigned int pindex, size = primes[0];
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/* Check requested hashtable isn't too large */
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if (minsize > (1u << 30)) return NULL;
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/* Enforce size as prime */
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for (pindex=0; pindex < prime_table_length; pindex++) {
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if (primes[pindex] > minsize) { size = primes[pindex]; break; }
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}
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h = (struct hashtable *)malloc(sizeof(struct hashtable));
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if (NULL == h) return NULL; /*oom*/
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h->table = (struct entry **)malloc(sizeof(struct entry*) * size);
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if (NULL == h->table) { free(h); return NULL; } /*oom*/
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memset(h->table, 0, size * sizeof(struct entry *));
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h->tablelength = size;
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h->primeindex = pindex;
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h->entrycount = 0;
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h->hashfn = hashf;
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h->eqfn = eqf;
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h->loadlimit = (unsigned int) ceil(size * max_load_factor);
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return h;
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}
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/*****************************************************************************/
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unsigned int
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hash(struct hashtable *h, void *k)
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{
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/* Aim to protect against poor hash functions by adding logic here
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* - logic taken from java 1.4 hashtable source */
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unsigned int i = h->hashfn(k);
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i += ~(i << 9);
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i ^= ((i >> 14) | (i << 18)); /* >>> */
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i += (i << 4);
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i ^= ((i >> 10) | (i << 22)); /* >>> */
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return i;
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}
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/*****************************************************************************/
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static int
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hashtable_expand(struct hashtable *h)
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{
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/* Double the size of the table to accomodate more entries */
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struct entry **newtable;
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struct entry *e;
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struct entry **pE;
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unsigned int newsize, i, index;
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/* Check we're not hitting max capacity */
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if (h->primeindex == (prime_table_length - 1)) return 0;
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newsize = primes[++(h->primeindex)];
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newtable = (struct entry **)malloc(sizeof(struct entry*) * newsize);
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if (NULL != newtable)
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{
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memset(newtable, 0, newsize * sizeof(struct entry *));
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/* This algorithm is not 'stable'. ie. it reverses the list
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* when it transfers entries between the tables */
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for (i = 0; i < h->tablelength; i++) {
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while (NULL != (e = h->table[i])) {
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h->table[i] = e->next;
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index = indexFor(newsize,e->h);
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e->next = newtable[index];
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newtable[index] = e;
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}
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}
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free(h->table);
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h->table = newtable;
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}
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/* Plan B: realloc instead */
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else
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{
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newtable = (struct entry **)
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realloc(h->table, newsize * sizeof(struct entry *));
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if (NULL == newtable) { (h->primeindex)--; return 0; }
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h->table = newtable;
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memset(newtable[h->tablelength], 0, newsize - h->tablelength);
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for (i = 0; i < h->tablelength; i++) {
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for (pE = &(newtable[i]), e = *pE; e != NULL; e = *pE) {
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index = indexFor(newsize,e->h);
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if (index == i)
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{
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pE = &(e->next);
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}
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else
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{
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*pE = e->next;
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e->next = newtable[index];
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newtable[index] = e;
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}
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}
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}
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}
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h->tablelength = newsize;
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h->loadlimit = (unsigned int) ceil(newsize * max_load_factor);
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return -1;
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}
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/*****************************************************************************/
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unsigned int
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hashtable_count(struct hashtable *h)
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{
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return h->entrycount;
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}
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/*****************************************************************************/
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int
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hashtable_insert(struct hashtable *h, void *k, void *v)
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{
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/* This method allows duplicate keys - but they shouldn't be used */
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unsigned int index;
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struct entry *e;
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if (++(h->entrycount) > h->loadlimit)
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{
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/* Ignore the return value. If expand fails, we should
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* still try cramming just this value into the existing table
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* -- we may not have memory for a larger table, but one more
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* element may be ok. Next time we insert, we'll try expanding again.*/
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hashtable_expand(h);
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}
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e = (struct entry *)malloc(sizeof(struct entry));
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if (NULL == e) { --(h->entrycount); return 0; } /*oom*/
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e->h = hash(h,k);
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index = indexFor(h->tablelength,e->h);
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e->k = k;
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e->v = v;
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e->next = h->table[index];
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h->table[index] = e;
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return -1;
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}
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/*****************************************************************************/
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void * /* returns value associated with key */
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hashtable_search(struct hashtable *h, void *k)
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{
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struct entry *e;
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unsigned int hashvalue, index;
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hashvalue = hash(h,k);
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index = indexFor(h->tablelength,hashvalue);
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e = h->table[index];
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while (NULL != e)
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{
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/* Check hash value to short circuit heavier comparison */
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if ((hashvalue == e->h) && (h->eqfn(k, e->k))) return e->v;
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e = e->next;
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}
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return NULL;
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}
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/*****************************************************************************/
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void * /* returns value associated with key */
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hashtable_remove(struct hashtable *h, void *k)
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{
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/* TODO: consider compacting the table when the load factor drops enough,
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* or provide a 'compact' method. */
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struct entry *e;
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struct entry **pE;
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void *v;
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unsigned int hashvalue, index;
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hashvalue = hash(h,k);
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index = indexFor(h->tablelength,hash(h,k));
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pE = &(h->table[index]);
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e = *pE;
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while (NULL != e)
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{
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/* Check hash value to short circuit heavier comparison */
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if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
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{
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*pE = e->next;
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h->entrycount--;
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v = e->v;
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freekey(e->k);
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free(e);
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return v;
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}
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pE = &(e->next);
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e = e->next;
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}
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return NULL;
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}
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/*****************************************************************************/
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/* destroy */
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void
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hashtable_destroy(struct hashtable *h, int free_values)
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{
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unsigned int i;
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struct entry *e, *f;
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struct entry **table = h->table;
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if (free_values)
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{
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for (i = 0; i < h->tablelength; i++)
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{
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e = table[i];
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while (NULL != e)
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{ f = e; e = e->next; freekey(f->k); free(f->v); free(f); }
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}
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}
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else
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{
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for (i = 0; i < h->tablelength; i++)
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{
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e = table[i];
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while (NULL != e)
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{ f = e; e = e->next; freekey(f->k); free(f); }
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}
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}
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free(h->table);
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free(h);
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}
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/*
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* Copyright (c) 2002, Christopher Clark
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* * Neither the name of the original author; nor the names of any contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
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* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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