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/*
* hashtbl.c
*
* Efficient symbol hash table class.
*/
#include <inttypes.h>
#include <string.h>
#include <stdlib.h>
#include "hashtbl.h"
#define HASH_MAX_LOAD 2 /* Higher = more memory-efficient, slower */
static struct hash_symbol **alloc_table(size_t newsize)
{
return calloc(sizeof(struct hash_symbol *), newsize);
}
void hash_init(struct hash_table *head, size_t size)
{
head->table = alloc_table(size);
head->load = 0;
head->size = size;
head->max_load = size*(HASH_MAX_LOAD-1)/HASH_MAX_LOAD;
}
/*
* Find an entry in a hash table.
*
* On failure, if "insert" is non-NULL, store data in that structure
* which can be used to insert that node using hash_add().
*
* WARNING: this data is only valid until the very next call of
* hash_add(); it cannot be "saved" to a later date.
*
* On success, return the hash_symbol pointer.
*/
struct hash_symbol *hash_find(struct hash_table *head, const char *key,
struct hash_insert *insert)
{
struct hash_symbol *np;
uint64_t hash = crc64(CRC64_INIT, key);
struct hash_symbol **tbl = head->table;
size_t mask = head->size-1;
size_t pos = hash & mask;
size_t inc = ((hash >> 32) & mask) | 1; /* Always odd */
while ((np = tbl[pos])) {
if (hash == np->hash && !strcmp(key, np->key))
return np;
pos = (pos+inc) & mask;
}
/* Not found. Store info for insert if requested. */
if (insert) {
insert->head = head;
insert->hash = hash;
insert->where = &tbl[pos];
}
return NULL;
}
/*
* Same as hash_find, but for case-insensitive hashing.
*/
struct hash_symbol *hash_findi(struct hash_table *head, const char *key,
struct hash_insert *insert)
{
struct hash_symbol *np;
uint64_t hash = crc64i(CRC64_INIT, key);
struct hash_symbol **tbl = head->table;
size_t mask = head->size-1;
size_t pos = hash & mask;
size_t inc = ((hash >> 32) & mask) | 1; /* Always odd */
while ((np = tbl[pos])) {
if (hash == np->hash && !strcasecmp(key, np->key))
return np;
pos = (pos+inc) & mask;
}
/* Not found. Store info for insert if requested. */
if (insert) {
insert->head = head;
insert->hash = hash;
insert->where = &tbl[pos];
}
return NULL;
}
/*
* Insert node.
*/
void hash_add(struct hash_insert *insert, struct hash_symbol *sym)
{
struct hash_table *head = insert->head;
struct hash_symbol **np = insert->where;
/* Insert node. We can always do this, even if we need to
rebalance immediately after. */
sym->hash = insert->hash;
*np = sym;
if (++head->load > head->max_load) {
/* Need to expand the table */
size_t newsize = head->size << 1;
struct hash_symbol **newtbl = alloc_table(newsize);
size_t mask = newsize-1;
if (head->table) {
struct hash_symbol **op, **xp;
size_t i, pos, inc;
uint64_t hash;
/* Rebalance all the entries */
for (i = 0, op = head->table; i < head->size;
i++, op++) {
if (*op) {
hash = (*op)->hash;
pos = hash & mask;
inc = ((hash >> 32) & mask) | 1;
while (*(xp = &newtbl[pos]))
pos = (pos+inc) & mask;
*xp = *op;
}
}
free(head->table);
}
head->table = newtbl;
head->size = newsize;
head->max_load = newsize*(HASH_MAX_LOAD-1)/HASH_MAX_LOAD;
}
}
/*
* Free the hash itself. Doesn't free the data elements; use
* hash_iterate() to do that first, if needed.
*/
void hash_free(struct hash_table *head)
{
void *p = head->table;
memset(head, 0, sizeof *head);
free(p);
}
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