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#define _GNU_SOURCE
#include <stdlib.h>
#include <string.h>
#include <search.h>
/*
open addressing hash table with 2^n table size
quadratic probing is used in case of hash collision
tab indices and hash are size_t
after resize fails with ENOMEM the state of tab is still usable
with the posix api items cannot be iterated and length cannot be queried
*/
#define MINSIZE 8
#define MAXSIZE ((size_t)-1/2 + 1)
struct __tab {
ENTRY *entries;
size_t mask;
size_t used;
};
static struct hsearch_data htab;
static int __hcreate_r(size_t, struct hsearch_data *);
static void __hdestroy_r(struct hsearch_data *);
static int __hsearch_r(ENTRY, ACTION, ENTRY **, struct hsearch_data *);
static size_t keyhash(char *k)
{
unsigned char *p = (void *)k;
size_t h = 0;
while (*p)
h = 31*h + *p++;
return h;
}
static int resize(size_t nel, struct hsearch_data *htab)
{
size_t newsize;
size_t i, j;
size_t oldsize = htab->__tab->mask + 1;
ENTRY *e, *newe;
ENTRY *oldtab = htab->__tab->entries;
if (nel > MAXSIZE)
nel = MAXSIZE;
for (newsize = MINSIZE; newsize < nel; newsize *= 2);
htab->__tab->entries = calloc(newsize, sizeof *htab->__tab->entries);
if (!htab->__tab->entries) {
htab->__tab->entries = oldtab;
return 0;
}
htab->__tab->mask = newsize - 1;
if (!oldtab)
return 1;
for (e = oldtab; e < oldtab + oldsize; e++)
if (e->key) {
for (i=keyhash(e->key),j=1; ; i+=j++) {
newe = htab->__tab->entries + (i & htab->__tab->mask);
if (!newe->key)
break;
}
*newe = *e;
}
free(oldtab);
return 1;
}
int hcreate(size_t nel)
{
return __hcreate_r(nel, &htab);
}
void hdestroy(void)
{
__hdestroy_r(&htab);
}
static ENTRY *lookup(char *key, size_t hash, struct hsearch_data *htab)
{
size_t i, j;
ENTRY *e;
for (i=hash,j=1; ; i+=j++) {
e = htab->__tab->entries + (i & htab->__tab->mask);
if (!e->key || strcmp(e->key, key) == 0)
break;
}
return e;
}
ENTRY *hsearch(ENTRY item, ACTION action)
{
ENTRY *e;
__hsearch_r(item, action, &e, &htab);
return e;
}
static int __hcreate_r(size_t nel, struct hsearch_data *htab)
{
int r;
htab->__tab = calloc(1, sizeof *htab->__tab);
if (!htab->__tab)
return 0;
r = resize(nel, htab);
if (r == 0) {
free(htab->__tab);
htab->__tab = 0;
}
return r;
}
weak_alias(__hcreate_r, hcreate_r);
static void __hdestroy_r(struct hsearch_data *htab)
{
if (htab->__tab) free(htab->__tab->entries);
free(htab->__tab);
htab->__tab = 0;
}
weak_alias(__hdestroy_r, hdestroy_r);
static int __hsearch_r(ENTRY item, ACTION action, ENTRY **retval, struct hsearch_data *htab)
{
size_t hash = keyhash(item.key);
ENTRY *e = lookup(item.key, hash, htab);
if (e->key) {
*retval = e;
return 1;
}
if (action == FIND) {
*retval = 0;
return 0;
}
*e = item;
if (++htab->__tab->used > htab->__tab->mask - htab->__tab->mask/4) {
if (!resize(2*htab->__tab->used, htab)) {
htab->__tab->used--;
e->key = 0;
*retval = 0;
return 0;
}
e = lookup(item.key, hash, htab);
}
*retval = e;
return 1;
}
weak_alias(__hsearch_r, hsearch_r);
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