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-rw-r--r--libs/cairo/src/cairo-hash.c508
1 files changed, 508 insertions, 0 deletions
diff --git a/libs/cairo/src/cairo-hash.c b/libs/cairo/src/cairo-hash.c
new file mode 100644
index 000000000..7e24d930d
--- /dev/null
+++ b/libs/cairo/src/cairo-hash.c
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "cairoint.h"
+#include "cairo-error-private.h"
+
+/*
+ * An entry can be in one of three states:
+ *
+ * FREE: Entry has never been used, terminates all searches.
+ * Appears in the table as a %NULL pointer.
+ *
+ * DEAD: Entry had been live in the past. A dead entry can be reused
+ * but does not terminate a search for an exact entry.
+ * Appears in the table as a pointer to DEAD_ENTRY.
+ *
+ * LIVE: Entry is currently being used.
+ * Appears in the table as any non-%NULL, non-DEAD_ENTRY pointer.
+ */
+
+#define DEAD_ENTRY ((cairo_hash_entry_t *) 0x1)
+
+#define ENTRY_IS_FREE(entry) ((entry) == NULL)
+#define ENTRY_IS_DEAD(entry) ((entry) == DEAD_ENTRY)
+#define ENTRY_IS_LIVE(entry) ((entry) > DEAD_ENTRY)
+
+/* We expect keys will not be destroyed frequently, so our table does not
+ * contain any explicit shrinking code nor any chain-coalescing code for
+ * entries randomly deleted by memory pressure (except during rehashing, of
+ * course). These assumptions are potentially bad, but they make the
+ * implementation straightforward.
+ *
+ * Revisit later if evidence appears that we're using excessive memory from
+ * a mostly-dead table.
+ *
+ * This table is open-addressed with double hashing. Each table size is a
+ * prime chosen to be a little more than double the high water mark for a
+ * given arrangement, so the tables should remain < 50% full. The table
+ * size makes for the "first" hash modulus; a second prime (2 less than the
+ * first prime) serves as the "second" hash modulus, which is co-prime and
+ * thus guarantees a complete permutation of table indices.
+ *
+ * This structure, and accompanying table, is borrowed/modified from the
+ * file xserver/render/glyph.c in the freedesktop.org x server, with
+ * permission (and suggested modification of doubling sizes) by Keith
+ * Packard.
+ */
+
+typedef struct _cairo_hash_table_arrangement {
+ unsigned long high_water_mark;
+ unsigned long size;
+ unsigned long rehash;
+} cairo_hash_table_arrangement_t;
+
+static const cairo_hash_table_arrangement_t hash_table_arrangements [] = {
+ { 16, 43, 41 },
+ { 32, 73, 71 },
+ { 64, 151, 149 },
+ { 128, 283, 281 },
+ { 256, 571, 569 },
+ { 512, 1153, 1151 },
+ { 1024, 2269, 2267 },
+ { 2048, 4519, 4517 },
+ { 4096, 9013, 9011 },
+ { 8192, 18043, 18041 },
+ { 16384, 36109, 36107 },
+ { 32768, 72091, 72089 },
+ { 65536, 144409, 144407 },
+ { 131072, 288361, 288359 },
+ { 262144, 576883, 576881 },
+ { 524288, 1153459, 1153457 },
+ { 1048576, 2307163, 2307161 },
+ { 2097152, 4613893, 4613891 },
+ { 4194304, 9227641, 9227639 },
+ { 8388608, 18455029, 18455027 },
+ { 16777216, 36911011, 36911009 },
+ { 33554432, 73819861, 73819859 },
+ { 67108864, 147639589, 147639587 },
+ { 134217728, 295279081, 295279079 },
+ { 268435456, 590559793, 590559791 }
+};
+
+#define NUM_HASH_TABLE_ARRANGEMENTS ARRAY_LENGTH (hash_table_arrangements)
+
+struct _cairo_hash_table {
+ cairo_hash_keys_equal_func_t keys_equal;
+
+ const cairo_hash_table_arrangement_t *arrangement;
+ cairo_hash_entry_t **entries;
+
+ unsigned long live_entries;
+ unsigned long iterating; /* Iterating, no insert, no resize */
+};
+
+/**
+ * _cairo_hash_table_create:
+ * @keys_equal: a function to return %TRUE if two keys are equal
+ *
+ * Creates a new hash table which will use the keys_equal() function
+ * to compare hash keys. Data is provided to the hash table in the
+ * form of user-derived versions of #cairo_hash_entry_t. A hash entry
+ * must be able to hold both a key (including a hash code) and a
+ * value. Sometimes only the key will be necessary, (as in
+ * _cairo_hash_table_remove), and other times both a key and a value
+ * will be necessary, (as in _cairo_hash_table_insert).
+ *
+ * See #cairo_hash_entry_t for more details.
+ *
+ * Return value: the new hash table or %NULL if out of memory.
+ **/
+cairo_hash_table_t *
+_cairo_hash_table_create (cairo_hash_keys_equal_func_t keys_equal)
+{
+ cairo_hash_table_t *hash_table;
+
+ hash_table = malloc (sizeof (cairo_hash_table_t));
+ if (unlikely (hash_table == NULL)) {
+ _cairo_error_throw (CAIRO_STATUS_NO_MEMORY);
+ return NULL;
+ }
+
+ hash_table->keys_equal = keys_equal;
+
+ hash_table->arrangement = &hash_table_arrangements[0];
+
+ hash_table->entries = calloc (hash_table->arrangement->size,
+ sizeof(cairo_hash_entry_t *));
+ if (unlikely (hash_table->entries == NULL)) {
+ _cairo_error_throw (CAIRO_STATUS_NO_MEMORY);
+ free (hash_table);
+ return NULL;
+ }
+
+ hash_table->live_entries = 0;
+ hash_table->iterating = 0;
+
+ return hash_table;
+}
+
+/**
+ * _cairo_hash_table_destroy:
+ * @hash_table: an empty hash table to destroy
+ *
+ * Immediately destroys the given hash table, freeing all resources
+ * associated with it.
+ *
+ * WARNING: The hash_table must have no live entries in it before
+ * _cairo_hash_table_destroy is called. It is a fatal error otherwise,
+ * and this function will halt. The rationale for this behavior is to
+ * avoid memory leaks and to avoid needless complication of the API
+ * with destroy notifiy callbacks.
+ *
+ * WARNING: The hash_table must have no running iterators in it when
+ * _cairo_hash_table_destroy is called. It is a fatal error otherwise,
+ * and this function will halt.
+ **/
+void
+_cairo_hash_table_destroy (cairo_hash_table_t *hash_table)
+{
+ /* The hash table must be empty. Otherwise, halt. */
+ assert (hash_table->live_entries == 0);
+ /* No iterators can be running. Otherwise, halt. */
+ assert (hash_table->iterating == 0);
+
+ free (hash_table->entries);
+ hash_table->entries = NULL;
+
+ free (hash_table);
+}
+
+static cairo_hash_entry_t **
+_cairo_hash_table_lookup_unique_key (cairo_hash_table_t *hash_table,
+ cairo_hash_entry_t *key)
+{
+ unsigned long table_size, i, idx, step;
+ cairo_hash_entry_t **entry;
+
+ table_size = hash_table->arrangement->size;
+ idx = key->hash % table_size;
+
+ entry = &hash_table->entries[idx];
+ if (! ENTRY_IS_LIVE (*entry))
+ return entry;
+
+ 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))
+ return entry;
+ } while (++i < table_size);
+
+ ASSERT_NOT_REACHED;
+ return NULL;
+}
+
+/**
+ * _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;
+ 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 (unlikely (tmp.entries == NULL))
+ return _cairo_error (CAIRO_STATUS_NO_MEMORY);
+
+ for (i = 0; i < hash_table->arrangement->size; ++i) {
+ if (ENTRY_IS_LIVE (hash_table->entries[i])) {
+ *_cairo_hash_table_lookup_unique_key (&tmp, hash_table->entries[i])
+ = hash_table->entries[i];
+ }
+ }
+
+ free (hash_table->entries);
+ hash_table->entries = tmp.entries;
+ hash_table->arrangement = tmp.arrangement;
+
+ return CAIRO_STATUS_SUCCESS;
+}
+
+/**
+ * _cairo_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 _cairo_hash_table_create).
+ *
+ * Return value: the matching entry, of %NULL if no match was found.
+ **/
+void *
+_cairo_hash_table_lookup (cairo_hash_table_t *hash_table,
+ cairo_hash_entry_t *key)
+{
+ cairo_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 (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 (hash_table->keys_equal (key, entry))
+ return entry;
+ } else if (ENTRY_IS_FREE (entry))
+ return NULL;
+ } while (++i < table_size);
+
+ return NULL;
+}
+
+/**
+ * _cairo_hash_table_random_entry:
+ * @hash_table: a hash table
+ * @predicate: a predicate function.
+ *
+ * Find a random entry in the hash table satisfying the given
+ * @predicate.
+ *
+ * We use the same algorithm as the lookup algorithm to walk over the
+ * entries in the hash table in a pseudo-random order. Walking
+ * linearly would favor entries following gaps in the hash table. We
+ * could also call rand() repeatedly, which works well for almost-full
+ * tables, but degrades when the table is almost empty, or predicate
+ * returns %TRUE for most entries.
+ *
+ * Return value: a random live entry or %NULL if there are no entries
+ * that match the given predicate. In particular, if predicate is
+ * %NULL, a %NULL return value indicates that the table is empty.
+ **/
+void *
+_cairo_hash_table_random_entry (cairo_hash_table_t *hash_table,
+ cairo_hash_predicate_func_t predicate)
+{
+ cairo_hash_entry_t *entry;
+ unsigned long hash;
+ unsigned long table_size, i, idx, step;
+
+ assert (predicate != NULL);
+
+ table_size = hash_table->arrangement->size;
+ hash = rand ();
+ idx = hash % table_size;
+
+ entry = hash_table->entries[idx];
+ if (ENTRY_IS_LIVE (entry) && predicate (entry))
+ return entry;
+
+ i = 1;
+ step = 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) && predicate (entry))
+ return entry;
+ } while (++i < table_size);
+
+ return NULL;
+}
+
+/**
+ * _cairo_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 _cairo_hash_table_lookup. Or if absolutely
+ * necessary, use _cairo_hash_table_remove first.
+ *
+ * Return value: %CAIRO_STATUS_SUCCESS if successful or
+ * %CAIRO_STATUS_NO_MEMORY if insufficient memory is available.
+ **/
+cairo_status_t
+_cairo_hash_table_insert (cairo_hash_table_t *hash_table,
+ cairo_hash_entry_t *key_and_value)
+{
+ cairo_status_t status;
+
+ /* Insert is illegal while an iterator is running. */
+ assert (hash_table->iterating == 0);
+
+ hash_table->live_entries++;
+ status = _cairo_hash_table_resize (hash_table);
+ if (unlikely (status)) {
+ /* abort the insert... */
+ hash_table->live_entries--;
+ return status;
+ }
+
+ *_cairo_hash_table_lookup_unique_key (hash_table,
+ key_and_value) = key_and_value;
+
+ return CAIRO_STATUS_SUCCESS;
+}
+
+static cairo_hash_entry_t **
+_cairo_hash_table_lookup_exact_key (cairo_hash_table_t *hash_table,
+ cairo_hash_entry_t *key)
+{
+ unsigned long table_size, i, idx, step;
+ cairo_hash_entry_t **entry;
+
+ table_size = hash_table->arrangement->size;
+ idx = key->hash % table_size;
+
+ entry = &hash_table->entries[idx];
+ if (*entry == key)
+ return entry;
+
+ 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 == key)
+ return entry;
+ } while (++i < table_size);
+
+ ASSERT_NOT_REACHED;
+ return NULL;
+}
+/**
+ * _cairo_hash_table_remove:
+ * @hash_table: a hash table
+ * @key: key of entry to be removed
+ *
+ * Remove an entry from the hash table which points to @key.
+ *
+ * Return value: %CAIRO_STATUS_SUCCESS if successful or
+ * %CAIRO_STATUS_NO_MEMORY if out of memory.
+ **/
+void
+_cairo_hash_table_remove (cairo_hash_table_t *hash_table,
+ cairo_hash_entry_t *key)
+{
+ *_cairo_hash_table_lookup_exact_key (hash_table, key) = DEAD_ENTRY;
+ hash_table->live_entries--;
+
+ /* Check for table resize. Don't do this when iterating as this will
+ * reorder elements of the table and cause the iteration to potentially
+ * skip some elements. */
+ if (hash_table->iterating == 0) {
+ /* This call _can_ fail, but only in failing to allocate new
+ * memory to shrink the hash table. It does leave the table in a
+ * consistent state, and we've already succeeded in removing the
+ * entry, so we don't examine the failure status of this call. */
+ _cairo_hash_table_resize (hash_table);
+ }
+}
+
+/**
+ * _cairo_hash_table_foreach:
+ * @hash_table: a hash table
+ * @hash_callback: function to be called for each live entry
+ * @closure: additional argument to be passed to @hash_callback
+ *
+ * Call @hash_callback for each live entry in the hash table, in a
+ * non-specified order.
+ *
+ * Entries in @hash_table may be removed by code executed from @hash_callback.
+ *
+ * Entries may not be inserted to @hash_table, nor may @hash_table
+ * be destroyed by code executed from @hash_callback. The relevant
+ * functions will halt in these cases.
+ **/
+void
+_cairo_hash_table_foreach (cairo_hash_table_t *hash_table,
+ cairo_hash_callback_func_t hash_callback,
+ void *closure)
+{
+ unsigned long i;
+ cairo_hash_entry_t *entry;
+
+ /* Mark the table for iteration */
+ ++hash_table->iterating;
+ for (i = 0; i < hash_table->arrangement->size; i++) {
+ entry = hash_table->entries[i];
+ if (ENTRY_IS_LIVE(entry))
+ hash_callback (entry, closure);
+ }
+ /* If some elements were deleted during the iteration,
+ * the table may need resizing. Just do this every time
+ * as the check is inexpensive.
+ */
+ if (--hash_table->iterating == 0) {
+ /* Should we fail to shrink the hash table, it is left unaltered,
+ * and we don't need to propagate the error status. */
+ _cairo_hash_table_resize (hash_table);
+ }
+}
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