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stringshare_del optimization. 

trade off safety by speed, we will always assume str was previously
shared, like evas_stringshare_del() did and we can know with zero-cost
the number of references and can avoid strlen() too.

When references drop to zero we still have to do the hash, access the
bucket and then lookup the Red-Black tree, then walk the list of
nodes, but avoiding so would use more memory, unacceptable at this
point.



SVN revision: 37268
This commit is contained in:
Gustavo Sverzut Barbieri 2008-10-28 12:23:12 +00:00
parent 9a0b7ebd18
commit 3cd98b547a
1 changed files with 42 additions and 34 deletions
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76
legacy/eina/src/lib/eina_stringshare.c
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@ -814,6 +814,9 @@ eina_stringshare_add(const char *str)
* if it exists. If that counter reaches 0, the memory associated to
* @p str is freed. If @p str is NULL, the function returns
* immediatly.
*
* Note that if the given pointer is not shared or NULL, bad things
* will happen, likely a segmentation fault.
*/
EAPI void
eina_stringshare_del(const char *str)
@ -821,31 +824,43 @@ eina_stringshare_del(const char *str)
Eina_Stringshare_Head *ed;
Eina_Stringshare_Node *el;
Eina_Stringshare_Node *prev;
Eina_Stringshare_Node *node;
int hash_num, slen, hash;
if (!str) return;
slen = strlen(str) + 1;
/* special cases */
if (str[0] == '\0') slen = 0;
else if (str[1] == '\0') slen = 1;
else if (str[2] == '\0') slen = 2;
else if (str[3] == '\0') slen = 3;
else slen = 4; /* handled later */
#ifdef EINA_STRINGSHARE_USAGE
population.count--;
if (slen <= 5)
population_group[slen - 1].count--;
if (slen < 4)
population_group[slen].count--;
#endif
switch (slen)
if (slen < 2)
return;
else if (slen < 4)
{
case 1:
case 2:
return ;
case 3:
case 4:
_eina_stringshare_small_del(str, slen - 1);
return;
default:
break;
_eina_stringshare_small_del(str, slen);
return;
}
node = (void *)(str - sizeof(Eina_Stringshare_Node));
EINA_MAGIC_CHECK_STRINGSHARE_NODE(node);
if (node->references > 1)
{
node->references--;
return;
}
node->references = 0;
slen = node->length; /* already includes '\0' */
hash = eina_hash_superfast(str, slen);
hash_num = hash & 0xFF;
hash = (hash >> 8) & EINA_STRINGSHARE_MASK;
@ -857,39 +872,32 @@ eina_stringshare_del(const char *str)
EINA_MAGIC_CHECK_STRINGSHARE_HEAD(ed);
for (prev = NULL, el = ed->head;
el && (const char*) (el + 1) != str;
prev = el, el = el->next)
for (prev = NULL, el = ed->head; el && el != node; prev = el, el = el->next)
;
if (!el) goto on_error;
EINA_MAGIC_CHECK_STRINGSHARE_NODE(el);
el->references--;
if (el->references == 0)
{
if (prev) prev->next = el->next;
else ed->head = el->next;
if (el->begin == EINA_FALSE)
MAGIC_FREE(el);
if (prev) prev->next = el->next;
else ed->head = el->next;
if (el->begin == EINA_FALSE)
MAGIC_FREE(el);
#ifdef EINA_STRINGSHARE_USAGE
ed->population--;
ed->population--;
#endif
if (ed->head == NULL)
{
share->buckets[hash_num] = (Eina_Stringshare_Head*) eina_rbtree_inline_remove(EINA_RBTREE_GET(share->buckets[hash_num]),
EINA_RBTREE_GET(ed),
EINA_RBTREE_CMP_NODE_CB(_eina_stringshare_node),
NULL);
MAGIC_FREE(ed);
}
if (ed->head == NULL)
{
share->buckets[hash_num] = (Eina_Stringshare_Head*) eina_rbtree_inline_remove(EINA_RBTREE_GET(share->buckets[hash_num]),
EINA_RBTREE_GET(ed),
EINA_RBTREE_CMP_NODE_CB(_eina_stringshare_node),
NULL);
MAGIC_FREE(ed);
}
return ;
on_error:
/* possible segfault happened before here, but... */
EINA_ERROR_PWARN("EEEK trying to del non-shared stringshare \"%s\"\n", str);
if (getenv("EINA_ERROR_ABORT")) abort();
}