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hash.c
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hash.c
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/* hash.c
A hash table implementation derived from lp_hash.c from the lp_solve library
to quickly translate a provided name to an index.
*/
#include <sys/types.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#include "hash.h"
#ifndef FALSE
# define FALSE 0
#endif
#ifndef TRUE
# define TRUE 1
#endif
#define HASH_START_SIZE 5000 /* Hash table size for row and column name storage */
#define NUMHASHPRIMES 45
hashtable *create_hash_table(int size, int base)
{
int i;
int HashPrimes[ ] = {
29, 229, 883, 1671, 2791, 4801, 8629, 10007,
15289, 25303, 34843, 65269, 99709, 129403, 147673, 166669,
201403, 222163, 242729, 261431, 303491, 320237, 402761, 501131,
602309, 701507, 800999, 900551, 1000619, 1100837, 1200359, 1300021,
1400017, 1500007, 1750009, 2000003, 2500009, 3000017, 4000037, 5000011,
6000011, 7000003, 8000009, 9000011, 9999991};
hashtable *ht;
/* Find a good size for the hash table */
if(size < HASH_START_SIZE)
size = HASH_START_SIZE;
for(i = 0; i < NUMHASHPRIMES-1; i++)
if(HashPrimes[i] > size)
break;
size = HashPrimes[i];
/* Then allocate and initialize memory */
ht = (hashtable *) calloc(1 , sizeof(*ht));
ht->table = (hashelem **) calloc(size, sizeof(*(ht->table)));
ht->size = size;
ht->base = base;
ht->count = base-1;
return(ht);
}
void free_hash_item(hashelem **hp)
{
free((*hp)->name);
free(*hp);
*hp = NULL;
}
void free_hash_table(hashtable *ht)
{
hashelem *hp, *thp;
hp = ht->first;
while(hp != NULL) {
thp = hp;
hp = hp->nextelem;
free_hash_item(&thp);
}
free(ht->table);
free(ht);
}
#ifndef CHAR_BIT
# define CHAR_BIT 8
#endif
/* make a good hash function for any int size */
/* inspired by Aho, Sethi and Ullman, Compilers ..., p436 */
#define HASH_1 sizeof(unsigned int)
#define HASH_2 (sizeof(unsigned int) * 6)
#define HASH_3 (((unsigned int)0xF0) << ((sizeof(unsigned int) - 1) * CHAR_BIT))
int hashval(const char *string, int size)
{
unsigned int result = 0, tmp;
for(; *string; string++) {
result = (result << HASH_1) + *string;
if((tmp = result & HASH_3) != 0) {
/* if any of the most significant bits is on */
result ^= tmp >> HASH_2; /* xor them in in a less significant part */
result ^= tmp; /* and reset the most significant bits to 0 */
}
}
return(result % size);
} /* hashval */
hashelem *findhash(const char *name, hashtable *ht)
{
hashelem *h_tab_p;
for(h_tab_p = ht->table[hashval(name, ht->size)];
h_tab_p != NULL;
h_tab_p = h_tab_p->next)
if(strcmp(name, h_tab_p->name) == 0) /* got it! */
break;
return(h_tab_p);
} /* findhash */
hashelem *puthash(const char *name, int index, hashelem **list, hashtable *ht)
{
hashelem *hp = NULL;
int hashindex;
if(list != NULL) {
hp = list[index];
if(hp != NULL)
list[index] = NULL;
}
if((hp = findhash(name, ht)) == NULL) {
hashindex = hashval(name, ht->size);
hp = (hashelem *) calloc(1, sizeof(*hp));
hp->name = strdup(name);
hp->index = index;
ht->count++;
if(list != NULL)
list[index] = hp;
hp->next = ht->table[hashindex];
ht->table[hashindex] = hp;
if(ht->first == NULL)
ht->first = hp;
if(ht->last != NULL)
ht->last->nextelem = hp;
ht->last = hp;
}
return(hp);
}
void drophash(const char *name, hashelem **list, hashtable *ht) {
hashelem *hp, *hp1, *hp2;
int hashindex;
if((hp = findhash(name, ht)) != NULL) {
hashindex = hashval(name, ht->size);
if((hp1 = ht->table[hashindex]) != NULL) {
hp2 = NULL;
while((hp1 != NULL) && (hp1 != hp)) {
hp2 = hp1;
hp1 = hp1->next;
}
if(hp1 == hp) {
if(hp2 != NULL)
hp2->next = hp->next;
else
ht->table[hashindex] = hp->next;
}
hp1 = ht->first;
hp2 = NULL;
while((hp1 != NULL) && (hp1 != hp)) {
hp2 = hp1;
hp1 = hp1->nextelem;
}
if(hp1 == hp) {
if(hp2 != NULL)
hp2->nextelem = hp->nextelem;
else {
ht->first = hp->nextelem;
if (ht->first == NULL)
ht->last = NULL;
}
}
if(list != NULL)
list[hp->index] = NULL;
free_hash_item(&hp);
ht->count--;
}
}
}
hashtable *copy_hash_table(hashtable *ht, hashelem **list, int newsize)
{
hashtable *copy;
hashelem *elem, *new_elem;
if(newsize < ht->size)
newsize = ht->size;
copy = create_hash_table(newsize, ht->base);
if (copy != NULL) {
elem = ht->first;
while (elem != NULL) {
if((new_elem = puthash(elem->name, elem->index, list, copy)) == NULL) {
free_hash_table(copy);
return(NULL);
}
elem = elem ->nextelem;
}
}
return(copy);
}
#if 0
int find_row(lprec *lp, char *name, MYBOOL Unconstrained_rows_found)
{
hashelem *hp;
hp = findhash(name, lp->rowname_hashtab);
if (hp == NULL) {
if(Unconstrained_rows_found) { /* just ignore them in this case */
return(-1);
}
else {
return(-1);
}
}
return(hp->index);
}
int find_var(lprec *lp, char *name, MYBOOL verbose)
{
hashelem *hp;
hp = findhash(name, lp->colname_hashtab);
if (hp == NULL) {
if(verbose)
report(lp, SEVERE, "find_var: Unknown variable name '%s'\n", name);
return(-1);
}
return(hp->index);
}
#endif