+++ /dev/null
-/**
- * \file mlt_profile.c
- * \brief least recently used cache
- * \see mlt_profile_s
- *
- * Copyright (C) 2007-2009 Ushodaya Enterprises Limited
- * \author Dan Dennedy <dan@dennedy.org>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library 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
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
- */
-
-#include "mlt_types.h"
-#include "mlt_log.h"
-#include "mlt_properties.h"
-#include "mlt_cache.h"
-
-#include <stdlib.h>
-#include <pthread.h>
-
-/** the maximum number of data objects to cache per line */
-#define CACHE_SIZE (10)
-
-/** \brief Cache item class
- *
- * A cache item is a structure holding information about a data object including
- * a reference count that is used to control its lifetime. When you get a
- * a cache item from the cache, you hold a reference that prevents the data
- * from being released when the cache is full and something new is added.
- * When you close the cache item, the reference count is decremented.
- * The data object is destroyed when all cache items are closed and the cache
- * releases its reference.
- */
-
-typedef struct mlt_cache_item_s
-{
- mlt_cache cache; /**< a reference to the cache to which this belongs */
- void *object; /**< a parent object to the cache data that uniquely identifies this cached item */
- void *data; /**< the opaque pointer to the cached data */
- int size; /**< the size of the cached data */
- int refcount; /**< a reference counter to control when destructor is called */
- mlt_destructor destructor; /**< a function to release or destroy the cached data */
-} mlt_cache_item_s;
-
-/** \brief Cache class
- *
- * This is a utility class for implementing a Least Recently Used (LRU) cache
- * of data blobs indexed by the address of some other object (e.g., a service).
- * Instead of sorting and manipulating linked lists, it tries to be simple and
- * elegant by copying pointers between two arrays of fixed size to shuffle the
- * order of elements.
- *
- * This class is useful if you have a service that wants to cache something
- * somewhat large, but will not scale if there are many instances of the service.
- * Of course, the service will need to know how to recreate the cached element
- * if it gets flushed from the cache,
- *
- * The most obvious examples are the pixbuf and qimage producers that cache their
- * respective objects representing a picture read from a file. If the picture
- * is no longer in the cache, it can simply re-read it from file. However, a
- * picture is often repeated over many frames and makes sense to cache instead
- * of continually reading, parsing, and decoding. On the other hand, you might
- * want to load hundreds of pictures as individual producers, which would use
- * a lot of memory if every picture is held in memory!
- */
-
-struct mlt_cache_s
-{
- int count; /**< the number of items currently in the cache */
- void* *current; /**< pointer to the current array of pointers */
- void* A[ CACHE_SIZE ];
- void* B[ CACHE_SIZE ];
- pthread_mutex_t mutex; /**< a mutex to prevent multi-threaded race conditions */
- mlt_properties active; /**< a list of cache items some of which may no longer
- be in \p current but to which there are
- outstanding references */
- mlt_properties garbage;/**< a list cache items pending release. A cache item
- is copied to this list when it is updated but there
- are outstanding references to the old data object. */
-};
-
-/** Get the data pointer from the cache item.
- *
- * \public \memberof mlt_cache_s
- * \param item a cache item
- * \param[out] size the number of bytes pointed at, if supplied when putting the data into the cache
- * \return the data pointer
- */
-
-void *mlt_cache_item_data( mlt_cache_item item, int *size )
-{
- if ( size && item )
- *size = item->size;
- return item? item->data : NULL;
-}
-
-/** Close a cache item given its parent object pointer.
- *
- * \private \memberof mlt_cache_s
- * \param cache a cache
- * \param object the object to which the data object belongs
- * \param data the data object, which might be in the garbage list (optional)
- */
-
-static void cache_object_close( mlt_cache cache, void *object, void* data )
-{
- char key[19];
-
- // Fetch the cache item from the active list by its owner's address
- sprintf( key, "%p", object );
- pthread_mutex_lock( &cache->mutex );
- mlt_cache_item item = mlt_properties_get_data( cache->active, key, NULL );
- if ( item )
- {
- mlt_log( NULL, MLT_LOG_DEBUG, "%s: item %p object %p data %p refcount %d\n", __FUNCTION__,
- item, item->object, item->data, item->refcount );
- if ( item->destructor && --item->refcount <= 0 )
- {
- // Destroy the data object
- item->destructor( item->data );
- item->data = NULL;
- item->destructor = NULL;
- // Do not dispose of the cache item because it could likely be used
- // again.
- }
- }
-
- // Fetch the cache item from the garbage collection by its data address
- if ( data )
- {
- sprintf( key, "%p", data );
- item = mlt_properties_get_data( cache->garbage, key, NULL );
- if ( item )
- {
- mlt_log( NULL, MLT_LOG_DEBUG, "collecting garbage item %p object %p data %p refcount %d\n",
- item, item->object, item->data, item->refcount );
- if ( item->destructor && --item->refcount <= 0 )
- {
- item->destructor( item->data );
- item->data = NULL;
- item->destructor = NULL;
- // We do not need the garbage-collected cache item
- mlt_properties_set_data( cache->garbage, key, NULL, 0, NULL, NULL );
- }
- }
- }
- pthread_mutex_unlock( &cache->mutex );
-}
-
-/** Close a cache item.
- *
- * Release a reference and call the destructor on the data object when all
- * references are released.
- *
- * \public \memberof mlt_cache_item_s
- * \param item a cache item
- */
-
-void mlt_cache_item_close( mlt_cache_item item )
-{
- if ( item )
- cache_object_close( item->cache, item->object, item->data );
-}
-
-/** Create a new cache.
- *
- * \public \memberof mlt_cache_s
- * \return a new cache or NULL if there was an error
- */
-
-mlt_cache mlt_cache_init()
-{
- mlt_cache result = calloc( 1, sizeof( struct mlt_cache_s ) );
- if ( result )
- {
- result->current = result->A;
- pthread_mutex_init( &result->mutex, NULL );
- result->active = mlt_properties_new();
- result->garbage = mlt_properties_new();
- }
- return result;
-}
-
-/** Destroy a cache.
- *
- * \public \memberof mlt_cache_s
- * \param cache the cache to detroy
- */
-
-void mlt_cache_close( mlt_cache cache )
-{
- if ( cache )
- {
- while ( cache->count-- )
- {
- void *object = cache->current[ cache->count ];
- mlt_log( NULL, MLT_LOG_DEBUG, "%s: %d = %p\n", __FUNCTION__, cache->count, object );
- cache_object_close( cache, object, NULL );
- }
- mlt_properties_close( cache->active );
- mlt_properties_close( cache->garbage );
- pthread_mutex_destroy( &cache->mutex );
- free( cache );
- }
-}
-
-/** Remove cache entries for an object.
- *
- * \public \memberof mlt_cache_s
- * \param cache a cache
- * \param object the object that owns the cached data
- */
-
-void mlt_cache_purge( mlt_cache cache, void *object )
-{
- pthread_mutex_lock( &cache->mutex );
- if ( cache && object )
- {
- int i, j;
- void **alt = cache->current == cache->A ? cache->B : cache->A;
-
- for ( i = 0, j = 0; i < cache->count; i++ )
- {
- void *o = cache->current[ i ];
-
- if ( o == object )
- {
- pthread_mutex_unlock( &cache->mutex );
- cache_object_close( cache, o, NULL );
- pthread_mutex_lock( &cache->mutex );
- }
- else
- {
- alt[ j++ ] = o;
- }
- }
- cache->count = j;
- cache->current = alt;
-
- // Remove the object's data from the active list regardless of refcount
- char key[19];
- sprintf( key, "%p", object );
- mlt_cache_item item = mlt_properties_get_data( cache->active, key, NULL );
- if ( item && item->destructor )
- {
- item->destructor( item->data );
- item->data = NULL;
- item->destructor = NULL;
- mlt_properties_set_data( cache->active, key, NULL, 0, NULL, NULL );
- }
-
- // Remove the object's items from the garbage collection regardless of refcount
- i = mlt_properties_count( cache->garbage );
- while ( i-- )
- {
- item = mlt_properties_get_data_at( cache->garbage, i, NULL );
- if ( object == item->object && item->destructor )
- {
- sprintf( key, "%p", item->data );
- item->destructor( item->data );
- item->data = NULL;
- item->destructor = NULL;
- mlt_properties_set_data( cache->garbage, key, NULL, 0, NULL, NULL );
- }
- }
- }
- pthread_mutex_unlock( &cache->mutex );
-}
-
-/** Shuffle the cache entries between the two arrays and return the cache entry for an object.
- *
- * \private \memberof mlt_cache_s
- * \param cache a cache object
- * \param object the object that owns the cached data
- * \return a cache entry if there was a hit or NULL for a miss
- */
-
-static void** shuffle_get_hit( mlt_cache cache, void *object )
-{
- int i = cache->count;
- int j = cache->count - 1;
- void **hit = NULL;
- void **alt = cache->current == cache->A ? cache->B : cache->A;
-
- if ( cache->count > 0 && cache->count < CACHE_SIZE )
- {
- // first determine if we have a hit
- while ( i-- && !hit )
- {
- void **o = &cache->current[ i ];
- if ( *o == object )
- hit = o;
- }
- // if there was no hit, we will not be shuffling out an entry
- // and are still filling the cache
- if ( !hit )
- ++j;
- // reset these
- i = cache->count;
- hit = NULL;
- }
-
- // shuffle the existing entries to the alternate array
- while ( i-- )
- {
- void **o = &cache->current[ i ];
-
- if ( !hit && *o == object )
- {
- hit = o;
- }
- else if ( j > 0 )
- {
- alt[ --j ] = *o;
-// mlt_log( NULL, MLT_LOG_DEBUG, "%s: shuffle %d = %p\n", __FUNCTION__, j, alt[j] );
- }
- }
- return hit;
-}
-
-/** Put a chunk of data in the cache.
- *
- * \public \memberof mlt_cache_s
- * \param cache a cache object
- * \param object the object to which this data belongs
- * \param data an opaque pointer to the data to cache
- * \param size the size of the data in bytes
- * \param destructor a pointer to a function that can destroy or release a reference to the data.
- */
-
-void mlt_cache_put( mlt_cache cache, void *object, void* data, int size, mlt_destructor destructor )
-{
- pthread_mutex_lock( &cache->mutex );
- void **hit = shuffle_get_hit( cache, object );
- void **alt = cache->current == cache->A ? cache->B : cache->A;
-
- // add the object to the cache
- if ( hit )
- {
- // release the old data
- pthread_mutex_unlock( &cache->mutex );
- cache_object_close( cache, *hit, NULL );
- pthread_mutex_lock( &cache->mutex );
- // the MRU end gets the updated data
- hit = &alt[ cache->count - 1 ];
- }
- else if ( cache->count < CACHE_SIZE )
- {
- // more room in cache, add it to MRU end
- hit = &alt[ cache->count++ ];
- }
- else
- {
- // release the entry at the LRU end
- pthread_mutex_unlock( &cache->mutex );
- cache_object_close( cache, cache->current[0], NULL );
- pthread_mutex_lock( &cache->mutex );
-
- // The MRU end gets the new item
- hit = &alt[ cache->count - 1 ];
- }
- *hit = object;
- mlt_log( NULL, MLT_LOG_DEBUG, "%s: put %d = %p, %p\n", __FUNCTION__, cache->count - 1, object, data );
-
- // Fetch the cache item
- char key[19];
- sprintf( key, "%p", object );
- mlt_cache_item item = mlt_properties_get_data( cache->active, key, NULL );
- if ( !item )
- {
- item = calloc( 1, sizeof( mlt_cache_item_s ) );
- if ( item )
- mlt_properties_set_data( cache->active, key, item, 0, free, NULL );
- }
- if ( item )
- {
- // If updating the cache item but not all references are released
- // copy the item to the garbage collection.
- if ( item->refcount > 0 && item->data )
- {
- mlt_cache_item orphan = calloc( 1, sizeof( mlt_cache_item_s ) );
- if ( orphan )
- {
- mlt_log( NULL, MLT_LOG_DEBUG, "adding to garbage collection object %p data %p\n", item->object, item->data );
- *orphan = *item;
- sprintf( key, "%p", orphan->data );
- // We store in the garbage collection by data address, not the owner's!
- mlt_properties_set_data( cache->garbage, key, orphan, 0, free, NULL );
- }
- }
-
- // Set/update the cache item
- item->cache = cache;
- item->object = object;
- item->data = data;
- item->size = size;
- item->destructor = destructor;
- item->refcount = 1;
- }
-
- // swap the current array
- cache->current = alt;
- pthread_mutex_unlock( &cache->mutex );
-}
-
-/** Get a chunk of data from the cache.
- *
- * \public \memberof mlt_cache_s
- * \param cache a cache object
- * \param object the object for which you are trying to locate the data
- * \return a mlt_cache_item if found or NULL if not found or has been flushed from the cache
- */
-
-mlt_cache_item mlt_cache_get( mlt_cache cache, void *object )
-{
- mlt_cache_item result = NULL;
- pthread_mutex_lock( &cache->mutex );
- void **hit = shuffle_get_hit( cache, object );
- void **alt = cache->current == cache->A ? cache->B : cache->A;
-
- if ( hit )
- {
- // copy the hit to the MRU end
- alt[ cache->count - 1 ] = *hit;
- hit = &alt[ cache->count - 1 ];
-
- char key[19];
- sprintf( key, "%p", *hit );
- result = mlt_properties_get_data( cache->active, key, NULL );
- if ( result && result->data )
- result->refcount++;
- mlt_log( NULL, MLT_LOG_DEBUG, "%s: get %d = %p, %p\n", __FUNCTION__, cache->count - 1, *hit, result->data );
-
- // swap the current array
- cache->current = alt;
- }
- pthread_mutex_unlock( &cache->mutex );
-
- return result;
-}
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