/** * _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; }