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/* Copyright (C) 2009 The Android Open Source Project
**
** This software is licensed under the terms of the GNU General Public
** License version 2, as published by the Free Software Foundation, and
** may be copied, distributed, and modified under those terms.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
*/
#include <android/utils/refset.h>
#include <stddef.h>
#define AREFSET_STEP 5
AINLINED uint32_t
_arefSet_hashItem( void* item )
{
uint32_t hash;
hash = (uint32_t)(ptrdiff_t)item >> 2;
if (sizeof(item) > 4)
hash ^= ((uint64_t)(ptrdiff_t)item >> 32);
return hash;
}
static void**
_arefSet_lookup( ARefSet* s, void* item)
{
uint32_t hash = _arefSet_hashItem(item);
unsigned index = hash & (s->max_buckets-1);
for (;;) {
void** pnode = &s->buckets[index];
if (*pnode == item || *pnode == NULL)
return pnode;
index += AREFSET_STEP;
if (index >= s->max_buckets)
index -= s->max_buckets;
}
}
static void**
_arefSet_lookupInsert( ARefSet* s, void* item)
{
uint32_t hash = _arefSet_hashItem(item);
unsigned index = hash & (s->max_buckets-1);
void** insert = NULL;
for (;;) {
void** pnode = &s->buckets[index];
if (*pnode == NULL) {
return insert ? insert : pnode;
} else if (*pnode == AREFSET_DELETED) {
if (!insert)
insert = pnode;
} else if (*pnode == item)
return pnode;
index = (index + AREFSET_STEP) & (s->max_buckets-1);
}
}
extern ABool
arefSet_has( ARefSet* s, void* item )
{
void** lookup;
if (item == NULL || s->max_buckets == 0)
return 0;
lookup = _arefSet_lookup(s, item);
return (*lookup == item);
}
/* the code below assumes, in the case of a down-size,
* that there aren't too many items in the set.
*/
static void
_arefSet_resize( ARefSet* s, unsigned newSize )
{
ARefSet newSet;
unsigned nn, count = s->num_buckets;
AVECTOR_INIT_ALLOC(&newSet,buckets, newSize);
for (nn = 0; nn < s->max_buckets; nn++) {
void* item = s->buckets[nn];
if (item != NULL && item != AREFSET_DELETED) {
void** lookup = _arefSet_lookup(&newSet, item);
*lookup = item;
}
}
AVECTOR_DONE(s,buckets);
s->buckets = newSet.buckets;
s->num_buckets = count;
s->max_buckets = newSet.max_buckets;
}
extern void
arefSet_add( ARefSet* s, void* item )
{
void** lookup;
if (item == NULL)
return;
/* You can't add items to a set during iteration! */
AASSERT(s->iteration == 0);
if (s->max_buckets == 0)
AVECTOR_INIT_ALLOC(s,buckets,4);
lookup = _arefSet_lookupInsert(s, item);
if (*lookup == item)
return;
*lookup = item;
s->num_buckets += 1;
if (s->iteration == 0) {
if (s->num_buckets > s->max_buckets*0.85)
_arefSet_resize(s, s->max_buckets*2);
}
}
extern void
arefSet_del( ARefSet* s, void* item )
{
void** lookup;
if (item == NULL || s->max_buckets == 0)
return;
lookup = _arefSet_lookup(s, item);
if (*lookup != item)
return;
if (s->iteration == 0) {
/* direct deletion */
*lookup = NULL;
s->num_buckets -= 1;
if (s->num_buckets < s->max_buckets*0.25)
_arefSet_resize(s, s->max_buckets/2);
} else {
/* deferred deletion */
*lookup = AREFSET_DELETED;
s->num_buckets -= 1;
s->iteration |= 1;
}
}
void
_arefSet_removeDeferred( ARefSet* s )
{
unsigned nn, newSize;
for (nn = 0; nn < s->max_buckets; nn++) {
if (s->buckets[nn] == AREFSET_DELETED) {
s->buckets[nn] = NULL;
}
}
s->iteration = 0;
newSize = s->max_buckets;
while (s->num_buckets < newSize*0.25)
newSize /= 2;
if (newSize != s->max_buckets)
_arefSet_resize(s, newSize);
}
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