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