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remove struct elem entirely from hsearch.c

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There are two changes here, both of which make sense to be done in a
single patch:

- Remove hash from struct elem and compute it at runtime wherever
  necessary.
- Eliminate struct elem and use ENTRY directly.

As a result we cut down on the memory usage as each element in the
hash table now contains only an ENTRY not an ENTRY + size_t for the
hash. The downside is that the hash needs to be computed at runtime.
This commit is contained in:
sin 2014-03-27 11:20:17 +00:00 • committed by Rich Felker
commit 141d3b5c2a
1 changed files with 22 additions and 29 deletions
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51
src/search/hsearch.c
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@ -16,13 +16,8 @@ with the posix api items cannot be iterated and length cannot be queried
#define MINSIZE 8 #define MINSIZE 8
#define MAXSIZE ((size_t)-1/2 + 1) #define MAXSIZE ((size_t)-1/2 + 1)
struct elem {
ENTRY item;
size_t hash;
};
struct __tab { struct __tab {
struct elem *elems; ENTRY *entries;
size_t mask; size_t mask;
size_t used; size_t used;
}; };
@ -47,26 +42,26 @@ static int resize(size_t nel, struct hsearch_data *htab)
{ {
size_t newsize; size_t newsize;
size_t i, j; size_t i, j;
struct elem *e, *newe; ENTRY *e, *newe;
struct elem *oldtab = htab->__tab->elems; ENTRY *oldtab = htab->__tab->entries;
struct elem *oldend = htab->__tab->elems + htab->__tab->mask + 1; ENTRY *oldend = htab->__tab->entries + htab->__tab->mask + 1;
if (nel > MAXSIZE) if (nel > MAXSIZE)
nel = MAXSIZE; nel = MAXSIZE;
for (newsize = MINSIZE; newsize < nel; newsize *= 2); for (newsize = MINSIZE; newsize < nel; newsize *= 2);
htab->__tab->elems = calloc(newsize, sizeof *htab->__tab->elems); htab->__tab->entries = calloc(newsize, sizeof *htab->__tab->entries);
if (!htab->__tab->elems) { if (!htab->__tab->entries) {
htab->__tab->elems = oldtab; htab->__tab->entries = oldtab;
return 0; return 0;
} }
htab->__tab->mask = newsize - 1; htab->__tab->mask = newsize - 1;
if (!oldtab) if (!oldtab)
return 1; return 1;
for (e = oldtab; e < oldend; e++) for (e = oldtab; e < oldend; e++)
if (e->item.key) { if (e->key) {
for (i=e->hash,j=1; ; i+=j++) { for (i=keyhash(e->key),j=1; ; i+=j++) {
newe = htab->__tab->elems + (i & htab->__tab->mask); newe = htab->__tab->entries + (i & htab->__tab->mask);
if (!newe->item.key) if (!newe->key)
break; break;
} }
*newe = *e; *newe = *e;
@ -85,15 +80,14 @@ void hdestroy(void)
__hdestroy_r(&htab); __hdestroy_r(&htab);
} }
static struct elem *lookup(char *key, size_t hash, struct hsearch_data *htab) static ENTRY *lookup(char *key, size_t hash, struct hsearch_data *htab)
{ {
size_t i, j; size_t i, j;
struct elem *e; ENTRY *e;
for (i=hash,j=1; ; i+=j++) { for (i=hash,j=1; ; i+=j++) {
e = htab->__tab->elems + (i & htab->__tab->mask); e = htab->__tab->entries + (i & htab->__tab->mask);
if (!e->item.key || if (!e->key || strcmp(e->key, key) == 0)
(e->hash==hash && strcmp(e->item.key, key)==0))
break; break;
} }
return e; return e;
@ -125,7 +119,7 @@ weak_alias(__hcreate_r, hcreate_r);
void __hdestroy_r(struct hsearch_data *htab) void __hdestroy_r(struct hsearch_data *htab)
{ {
if (htab->__tab) free(htab->__tab->elems); if (htab->__tab) free(htab->__tab->entries);
free(htab->__tab); free(htab->__tab);
htab->__tab = 0; htab->__tab = 0;
} }
@ -134,28 +128,27 @@ weak_alias(__hdestroy_r, hdestroy_r);
int __hsearch_r(ENTRY item, ACTION action, ENTRY **retval, struct hsearch_data *htab) int __hsearch_r(ENTRY item, ACTION action, ENTRY **retval, struct hsearch_data *htab)
{ {
size_t hash = keyhash(item.key); size_t hash = keyhash(item.key);
struct elem *e = lookup(item.key, hash, htab); ENTRY *e = lookup(item.key, hash, htab);
if (e->item.key) { if (e->key) {
*retval = &e->item; *retval = e;
return 1; return 1;
} }
if (action == FIND) { if (action == FIND) {
*retval = 0; *retval = 0;
return 0; return 0;
} }
e->item = item; *e = item;
e->hash = hash;
if (++htab->__tab->used > htab->__tab->mask - htab->__tab->mask/4) { if (++htab->__tab->used > htab->__tab->mask - htab->__tab->mask/4) {
if (!resize(2*htab->__tab->used, htab)) { if (!resize(2*htab->__tab->used, htab)) {
htab->__tab->used--; htab->__tab->used--;
e->item.key = 0; e->key = 0;
*retval = 0; *retval = 0;
return 0; return 0;
} }
e = lookup(item.key, hash, htab); e = lookup(item.key, hash, htab);
} }
*retval = &e->item; *retval = e;
return 1; return 1;
} }
weak_alias(__hsearch_r, hsearch_r); weak_alias(__hsearch_r, hsearch_r);