/**
* _cairo_hash_table_resize:
* @hash_table: a hash table
*
* Resize the hash table if the number of entries has gotten much
* bigger or smaller than the ideal number of entries for the current
* size.
*
* Return value: CAIRO_STATUS_SUCCESS if successful or
* CAIRO_STATUS_NO_MEMORY if out of memory.
**/
static cairo_status_t
_cairo_hash_table_resize (cairo_hash_table_t *hash_table)
{
cairo_hash_table_t tmp;
cairo_hash_entry_t **entry;
unsigned long new_size, i;
/* This keeps the hash table between 25% and 50% full. */
unsigned long high = hash_table->arrangement->high_water_mark;
unsigned long low = high >> 2;
if (hash_table->live_entries >= low && hash_table->live_entries <= high)
return CAIRO_STATUS_SUCCESS;
tmp = *hash_table;
if (hash_table->live_entries > high)
{
tmp.arrangement = hash_table->arrangement + 1;
/* This code is being abused if we can't make a table big enough. */
assert (tmp.arrangement - hash_table_arrangements <
NUM_HASH_TABLE_ARRANGEMENTS);
}
else /* hash_table->live_entries < low */
{
/* Can't shrink if we're at the smallest size */
if (hash_table->arrangement == &hash_table_arrangements[0])
return CAIRO_STATUS_SUCCESS;
tmp.arrangement = hash_table->arrangement - 1;
}
new_size = tmp.arrangement->size;
tmp.entries = calloc (new_size, sizeof (cairo_hash_entry_t*));
if (tmp.entries == NULL)
return CAIRO_STATUS_NO_MEMORY;
for (i = 0; i < hash_table->arrangement->size; ++i) {
if (ENTRY_IS_LIVE (hash_table->entries[i])) {
entry = _cairo_hash_table_lookup_internal (&tmp,
hash_table->entries[i],
TRUE);
assert (ENTRY_IS_FREE(*entry));
*entry = hash_table->entries[i];
}
}
free (hash_table->entries);
hash_table->entries = tmp.entries;
hash_table->arrangement = tmp.arrangement;
return CAIRO_STATUS_SUCCESS;
}
/**
* _csi_hash_table_lookup:
* @hash_table: a hash table
* @key: the key of interest
*
* Performs a lookup in @hash_table looking for an entry which has a
* key that matches @key, (as determined by the keys_equal() function
* passed to _csi_hash_table_create).
*
* Return value: the matching entry, of %NULL if no match was found.
**/
void *
_csi_hash_table_lookup (csi_hash_table_t *hash_table,
csi_hash_entry_t *key)
{
csi_hash_entry_t **entry;
unsigned long table_size, i, idx, step;
table_size = hash_table->arrangement->size;
idx = key->hash % table_size;
entry = &hash_table->entries[idx];
if (ENTRY_IS_LIVE (*entry)) {
if ((*entry)->hash == key->hash && hash_table->keys_equal (key, *entry))
return *entry;
} else if (ENTRY_IS_FREE (*entry))
return NULL;
i = 1;
step = key->hash % hash_table->arrangement->rehash;
if (step == 0)
step = 1;
do {
idx += step;
if (idx >= table_size)
idx -= table_size;
entry = &hash_table->entries[idx];
if (ENTRY_IS_LIVE (*entry)) {
if ((*entry)->hash == key->hash &&
hash_table->keys_equal (key, *entry))
{
return *entry;
}
} else if (ENTRY_IS_FREE (*entry))
return NULL;
} while (++i < table_size);
return NULL;
}
/**
* _csi_hash_table_insert:
* @hash_table: a hash table
* @key_and_value: an entry to be inserted
*
* Insert the entry #key_and_value into the hash table.
*
* WARNING: There must not be an existing entry in the hash table
* with a matching key.
*
* WARNING: It is a fatal error to insert an element while
* an iterator is running
*
* Instead of using insert to replace an entry, consider just editing
* the entry obtained with _csi_hash_table_lookup. Or if absolutely
* necessary, use _csi_hash_table_remove first.
*
* Return value: %CAIRO_STATUS_SUCCESS if successful or
* %CAIRO_STATUS_NO_MEMORY if insufficient memory is available.
**/
csi_status_t
_csi_hash_table_insert (csi_hash_table_t *hash_table,
csi_hash_entry_t *key_and_value)
{
csi_status_t status;
csi_hash_entry_t **entry;
hash_table->live_entries++;
status = _csi_hash_table_manage (hash_table);
if (_csi_unlikely (status)) {
/* abort the insert... */
hash_table->live_entries--;
return status;
}
entry = _csi_hash_table_lookup_unique_key (hash_table,
key_and_value);
if (ENTRY_IS_FREE (*entry))
hash_table->used_entries++;
*entry = key_and_value;
return CAIRO_STATUS_SUCCESS;
}
/**
* _csi_hash_table_manage:
* @hash_table: a hash table
*
* Resize the hash table if the number of entries has gotten much
* bigger or smaller than the ideal number of entries for the current
* size, or control the number of dead entries by moving the entries
* within the table.
*
* Return value: %CAIRO_STATUS_SUCCESS if successful or
* %CAIRO_STATUS_NO_MEMORY if out of memory.
**/
static csi_status_t
_csi_hash_table_manage (csi_hash_table_t *hash_table)
{
csi_hash_table_t tmp;
csi_boolean_t realloc = TRUE;
unsigned long i;
/* This keeps the size of the hash table between 2 and approximately 8
* times the number of live entries and keeps the proportion of free
* entries (search-terminations) > 25%.
*/
unsigned long high = hash_table->arrangement->high_water_mark;
unsigned long low = high >> 2;
unsigned long max_used = high + high / 2;
tmp = *hash_table;
if (hash_table->live_entries > high) {
tmp.arrangement = hash_table->arrangement + 1;
/* This code is being abused if we can't make a table big enough. */
} else if (hash_table->live_entries < low &&
/* Can't shrink if we're at the smallest size */
hash_table->arrangement != &hash_table_arrangements[0])
{
tmp.arrangement = hash_table->arrangement - 1;
}
else if (hash_table->used_entries > max_used)
{
/* Clean out dead entries to prevent lookups from becoming too slow. */
for (i = 0; i < hash_table->arrangement->size; ++i) {
if (ENTRY_IS_DEAD (hash_table->entries[i]))
hash_table->entries[i] = NULL;
}
hash_table->used_entries = hash_table->live_entries;
/* There is no need to reallocate but some entries may need to be
* moved. Typically the proportion of entries needing to be moved is
* small, but, if the moving should leave a large number of dead
* entries, they will be cleaned out next time this code is
* executed. */
realloc = FALSE;
}
else
{
return CAIRO_STATUS_SUCCESS;
}
if (realloc) {
tmp.entries = calloc (tmp.arrangement->size,
sizeof (csi_hash_entry_t*));
if (tmp.entries == NULL)
return _csi_error (CAIRO_STATUS_NO_MEMORY);
hash_table->used_entries = 0;
}
for (i = 0; i < hash_table->arrangement->size; ++i) {
csi_hash_entry_t *entry, **pos;
entry = hash_table->entries[i];
if (ENTRY_IS_LIVE (entry)) {
hash_table->entries[i] = DEAD_ENTRY;
pos = _csi_hash_table_lookup_unique_key (&tmp, entry);
if (ENTRY_IS_FREE (*pos))
hash_table->used_entries++;
*pos = entry;
}
}
if (realloc) {
free (hash_table->entries);
hash_table->entries = tmp.entries;
hash_table->arrangement = tmp.arrangement;
}
return CAIRO_STATUS_SUCCESS;
}
