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/* cairo - a vector graphics library with display and print output
*
* Copyright © 2004 Red Hat, Inc.
* Copyright © 2005 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it either under the terms of the GNU Lesser General Public
* License version 2.1 as published by the Free Software Foundation
* (the "LGPL") or, at your option, under the terms of the Mozilla
* Public License Version 1.1 (the "MPL"). If you do not alter this
* notice, a recipient may use your version of this file under either
* the MPL or the LGPL.
*
* You should have received a copy of the LGPL along with this library
* in the file COPYING-LGPL-2.1; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
* You should have received a copy of the MPL along with this library
* in the file COPYING-MPL-1.1
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
* OF ANY KIND, either express or implied. See the LGPL or the MPL for
* the specific language governing rights and limitations.
*
* The Original Code is the cairo graphics library.
*
* The Initial Developer of the Original Code is Red Hat, Inc.
*
* Contributor(s):
* Keith Packard <keithp@keithp.com>
* Graydon Hoare <graydon@redhat.com>
* Carl Worth <cworth@cworth.org>
*/
#include "cairoint.h"
#include "cairo-error-private.h"
static void
_cairo_cache_shrink_to_accommodate (cairo_cache_t *cache,
unsigned long additional);
static cairo_bool_t
_cairo_cache_entry_is_non_zero (const void *entry)
{
return ((const cairo_cache_entry_t *) entry)->size;
}
/**
* _cairo_cache_init:
* @cache: the #cairo_cache_t to initialise
* @keys_equal: a function to return %TRUE if two keys are equal
* @entry_destroy: destroy notifier for cache entries
* @max_size: the maximum size for this cache
* Returns: the newly created #cairo_cache_t
*
* Creates a new cache using the keys_equal() function to determine
* the equality of entries.
*
* Data is provided to the cache in the form of user-derived version
* of #cairo_cache_entry_t. A cache entry must be able to hold hash
* code, a size, and the key/value pair being stored in the
* cache. Sometimes only the key will be necessary, (as in
* _cairo_cache_lookup()), and in these cases the value portion of the
* entry need not be initialized.
*
* The units for max_size can be chosen by the caller, but should be
* consistent with the units of the size field of cache entries. When
* adding an entry with _cairo_cache_insert() if the total size of
* entries in the cache would exceed max_size then entries will be
* removed at random until the new entry would fit or the cache is
* empty. Then the new entry is inserted.
*
* There are cases in which the automatic removal of entries is
* undesired. If the cache entries have reference counts, then it is a
* simple matter to use the reference counts to ensure that entries
* continue to live even after being ejected from the cache. However,
* in some cases the memory overhead of adding a reference count to
* the entry would be objectionable. In such cases, the
* _cairo_cache_freeze() and _cairo_cache_thaw() calls can be
* used to establish a window during which no automatic removal of
* entries will occur.
**/
cairo_status_t
_cairo_cache_init (cairo_cache_t *cache,
cairo_cache_keys_equal_func_t keys_equal,
cairo_cache_predicate_func_t predicate,
cairo_destroy_func_t entry_destroy,
unsigned long max_size)
{
cache->hash_table = _cairo_hash_table_create (keys_equal);
if (unlikely (cache->hash_table == NULL))
return _cairo_error (CAIRO_STATUS_NO_MEMORY);
if (predicate == NULL)
predicate = _cairo_cache_entry_is_non_zero;
cache->predicate = predicate;
cache->entry_destroy = entry_destroy;
cache->max_size = max_size;
cache->size = 0;
cache->freeze_count = 0;
return CAIRO_STATUS_SUCCESS;
}
static void
_cairo_cache_pluck (void *entry, void *closure)
{
_cairo_cache_remove (closure, entry);
}
/**
* _cairo_cache_fini:
* @cache: a cache to destroy
*
* Immediately destroys the given cache, freeing all resources
* associated with it. As part of this process, the entry_destroy()
* function, (as passed to _cairo_cache_init()), will be called for
* each entry in the cache.
**/
void
_cairo_cache_fini (cairo_cache_t *cache)
{
_cairo_hash_table_foreach (cache->hash_table,
_cairo_cache_pluck,
cache);
assert (cache->size == 0);
_cairo_hash_table_destroy (cache->hash_table);
}
/**
* _cairo_cache_freeze:
* @cache: a cache with some precious entries in it (or about to be
* added)
*
* Disable the automatic ejection of entries from the cache. For as
* long as the cache is "frozen", calls to _cairo_cache_insert() will
* add new entries to the cache regardless of how large the cache
* grows. See _cairo_cache_thaw().
*
* Note: Multiple calls to _cairo_cache_freeze() will stack, in that
* the cache will remain "frozen" until a corresponding number of
* calls are made to _cairo_cache_thaw().
**/
void
_cairo_cache_freeze (cairo_cache_t *cache)
{
assert (cache->freeze_count >= 0);
cache->freeze_count++;
}
/**
* _cairo_cache_thaw:
* @cache: a cache, just after the entries in it have become less
* precious
*
* Cancels the effects of _cairo_cache_freeze().
*
* When a number of calls to _cairo_cache_thaw() is made corresponding
* to the number of calls to _cairo_cache_freeze() the cache will no
* longer be "frozen". If the cache had grown larger than max_size
* while frozen, entries will immediately be ejected (by random) from
* the cache until the cache is smaller than max_size. Also, the
* automatic ejection of entries on _cairo_cache_insert() will resume.
**/
void
_cairo_cache_thaw (cairo_cache_t *cache)
{
assert (cache->freeze_count > 0);
if (--cache->freeze_count == 0)
_cairo_cache_shrink_to_accommodate (cache, 0);
}
/**
* _cairo_cache_lookup:
* @cache: a cache
* @key: the key of interest
* @entry_return: pointer for return value
*
* Performs a lookup in @cache looking for an entry which has a key
* that matches @key, (as determined by the keys_equal() function
* passed to _cairo_cache_init()).
*
* Return value: %TRUE if there is an entry in the cache that matches
* @key, (which will now be in *entry_return). %FALSE otherwise, (in
* which case *entry_return will be %NULL).
**/
void *
_cairo_cache_lookup (cairo_cache_t *cache,
cairo_cache_entry_t *key)
{
return _cairo_hash_table_lookup (cache->hash_table,
(cairo_hash_entry_t *) key);
}
/**
* _cairo_cache_remove_random:
* @cache: a cache
*
* Remove a random entry from the cache.
*
* Return value: %TRUE if an entry was successfully removed.
* %FALSE if there are no entries that can be removed.
**/
static cairo_bool_t
_cairo_cache_remove_random (cairo_cache_t *cache)
{
cairo_cache_entry_t *entry;
entry = _cairo_hash_table_random_entry (cache->hash_table,
cache->predicate);
if (unlikely (entry == NULL))
return FALSE;
_cairo_cache_remove (cache, entry);
return TRUE;
}
/**
* _cairo_cache_shrink_to_accommodate:
* @cache: a cache
* @additional: additional size requested in bytes
*
* If cache is not frozen, eject entries randomly until the size of
* the cache is at least @additional bytes less than
* cache->max_size. That is, make enough room to accommodate a new
* entry of size @additional.
**/
static void
_cairo_cache_shrink_to_accommodate (cairo_cache_t *cache,
unsigned long additional)
{
while (cache->size + additional > cache->max_size) {
if (! _cairo_cache_remove_random (cache))
return;
}
}
/**
* _cairo_cache_insert:
* @cache: a cache
* @entry: an entry to be inserted
*
* Insert @entry into the cache. If an entry exists in the cache with
* a matching key, then the old entry will be removed first, (and the
* entry_destroy() callback will be called on it).
*
* Return value: %CAIRO_STATUS_SUCCESS if successful or
* %CAIRO_STATUS_NO_MEMORY if insufficient memory is available.
**/
cairo_status_t
_cairo_cache_insert (cairo_cache_t *cache,
cairo_cache_entry_t *entry)
{
cairo_status_t status;
if (entry->size && ! cache->freeze_count)
_cairo_cache_shrink_to_accommodate (cache, entry->size);
status = _cairo_hash_table_insert (cache->hash_table,
(cairo_hash_entry_t *) entry);
if (unlikely (status))
return status;
cache->size += entry->size;
return CAIRO_STATUS_SUCCESS;
}
/**
* _cairo_cache_remove:
* @cache: a cache
* @entry: an entry that exists in the cache
*
* Remove an existing entry from the cache.
**/
void
_cairo_cache_remove (cairo_cache_t *cache,
cairo_cache_entry_t *entry)
{
cache->size -= entry->size;
_cairo_hash_table_remove (cache->hash_table,
(cairo_hash_entry_t *) entry);
if (cache->entry_destroy)
cache->entry_destroy (entry);
}
/**
* _cairo_cache_foreach:
* @cache: a cache
* @cache_callback: function to be called for each entry
* @closure: additional argument to be passed to @cache_callback
*
* Call @cache_callback for each entry in the cache, in a
* non-specified order.
**/
void
_cairo_cache_foreach (cairo_cache_t *cache,
cairo_cache_callback_func_t cache_callback,
void *closure)
{
_cairo_hash_table_foreach (cache->hash_table,
cache_callback,
closure);
}
unsigned long
_cairo_hash_string (const char *c)
{
/* This is the djb2 hash. */
unsigned long hash = _CAIRO_HASH_INIT_VALUE;
while (c && *c)
hash = ((hash << 5) + hash) + *c++;
return hash;
}
unsigned long
_cairo_hash_bytes (unsigned long hash,
const void *ptr,
unsigned int length)
{
const uint8_t *bytes = ptr;
/* This is the djb2 hash. */
while (length--)
hash = ((hash << 5) + hash) + *bytes++;
return hash;
}