[melted] / src / framework / mlt_pool.c

/**
 * \file mlt_pool.c
 * \brief memory pooling functionality
 * \see mlt_pool_s
 *
 * Copyright (C) 2003-2009 Ushodaya Enterprises Limited
 * \author Charles Yates <charles.yates@pandora.be>
 *
 * 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_properties.h"
#include "mlt_deque.h"

#include <stdlib.h>
#include <string.h>
#include <pthread.h>

// Not nice - memalign is defined here apparently?
#ifdef linux
#include <malloc.h>
#endif

/** global singleton for tracking pools */

static mlt_properties pools = NULL;

/** \brief Pool (memory) class
 */

typedef struct mlt_pool_s
{
        pthread_mutex_t lock; ///< lock to prevent race conditions
        mlt_deque stack;      ///< a stack of addresses to memory blocks
        int size;             ///< the size of the memory block as a power of 2
        int count;            ///< the number of blocks in the pool
}
*mlt_pool;

/** \brief private to mlt_pool_s, for tracking items to release
 */

typedef struct mlt_release_s
{
        mlt_pool pool;
        int references;
}
*mlt_release;

/** Create a pool.
 *
 * \private \memberof mlt_pool_s
 * \param size the size of the memory blocks to hold as some power of two
 * \return a new pool object
 */

static mlt_pool pool_init( int size )
{
        // Create the pool
        mlt_pool this = calloc( 1, sizeof( struct mlt_pool_s ) );

        // Initialise it
        if ( this != NULL )
        {
                // Initialise the mutex
                pthread_mutex_init( &this->lock, NULL );

                // Create the stack
                this->stack = mlt_deque_init( );

                // Assign the size
                this->size = size;
        }

        // Return it
        return this;
}

/** Get an item from the pool.
 *
 * \private \memberof mlt_pool_s
 * \param this a pool
 * \return an opaque pointer
 */

static void *pool_fetch( mlt_pool this )
{
        // We will generate a release object
        void *ptr = NULL;

        // Sanity check
        if ( this != NULL )
        {
                // Lock the pool
                pthread_mutex_lock( &this->lock );

                // Check if the stack is empty
                if ( mlt_deque_count( this->stack ) != 0 )
                {
                        // Pop the top of the stack
                        ptr = mlt_deque_pop_back( this->stack );

                        // Assign the reference
                        ( ( mlt_release )ptr )->references = 1;
                }
                else
                {
                        // We need to generate a release item
#ifdef linux
                        mlt_release release = memalign( 16, this->size );
#else
                        mlt_release release = malloc( this->size );
#endif

                        // Initialise it
                        if ( release != NULL )
                        {
                                // Increment the number of items allocated to this pool
                                this->count ++;

                                // Assign the pool
                                release->pool = this;

                                // Assign the reference
                                release->references = 1;

                                // Determine the ptr
                                ptr = ( void * )release + sizeof( struct mlt_release_s );
                        }
                }

                // Unlock the pool
                pthread_mutex_unlock( &this->lock );
        }

        // Return the generated release object
        return ptr;
}

/** Return an item to the pool.
 *
 * \private \memberof mlt_pool_s
 * \param ptr an opaque pointer
 */

static void pool_return( void *ptr )
{
        // Sanity checks
        if ( ptr != NULL )
        {
                // Get the release pointer
                mlt_release that = ptr - sizeof( struct mlt_release_s );

                // Get the pool
                mlt_pool this = that->pool;

                if ( this != NULL )
                {
                        // Lock the pool
                        pthread_mutex_lock( &this->lock );

                        // Push the that back back on to the stack
                        mlt_deque_push_back( this->stack, ptr );

                        // Unlock the pool
                        pthread_mutex_unlock( &this->lock );

                        // Ensure that we don't clean up
                        ptr = NULL;
                }
        }

        // Tidy up - this will only occur if the returned item is incorrect
        if ( ptr != NULL )
        {
                // Free the release itself
                free( ptr - sizeof( struct mlt_release_s ) );
        }
}

/** Destroy a pool.
 *
 * \private \memberof mlt_pool_s
 * \param this a pool
 */

static void pool_close( mlt_pool this )
{
        if ( this != NULL )
        {
                // We need to free up all items in the pool
                void *release = NULL;

                // Iterate through the stack until depleted
                while ( ( release = mlt_deque_pop_back( this->stack ) ) != NULL )
                {
                        // We'll free this item now
                        free( release - sizeof( struct mlt_release_s ) );
                }

                // We can now close the stack
                mlt_deque_close( this->stack );

                // Destroy the mutex
                pthread_mutex_destroy( &this->lock );

                // Close the pool
                free( this );
        }
}

/** Initialise the global pool.
 *
 * \public \memberof mlt_pool_s
 */

void mlt_pool_init( )
{
        // Loop variable used to create the pools
        int i = 0;

        // Create the pools
        pools = mlt_properties_new( );

        // Create the pools
        for ( i = 8; i < 31; i ++ )
        {
                // Each properties item needs a name
                char name[ 32 ];

                // Construct a pool
                mlt_pool pool = pool_init( 1 << i );

                // Generate a name
                sprintf( name, "%d", i );

                // Register with properties
                mlt_properties_set_data( pools, name, pool, 0, ( mlt_destructor )pool_close, NULL );
        }
}

/** Allocate size bytes from the pool.
 *
 * \public \memberof mlt_pool_s
 * \param size the number of bytes
 */

void *mlt_pool_alloc( int size )
{
        // This will be used to obtain the pool to use
        mlt_pool pool = NULL;

        // Determines the index of the pool to use
        int index = 8;

        // Minimum size pooled is 256 bytes
        size = size + sizeof( mlt_release );
        while ( ( 1 << index ) < size )
                index ++;

        // Now get the pool at the index
        pool = mlt_properties_get_data_at( pools, index - 8, NULL );

        // Now get the real item
        return pool_fetch( pool );
}

/** Allocate size bytes from the pool.
 *
 * \public \memberof mlt_pool_s
 * \param ptr an opaque pointer - can be in the pool or a new block to allocate
 * \param size the number of bytes
 */

void *mlt_pool_realloc( void *ptr, int size )
{
        // Result to return
        void *result = NULL;

        // Check if we actually have an address
        if ( ptr != NULL )
        {
                // Get the release pointer
                mlt_release that = ptr - sizeof( struct mlt_release_s );

                // If the current pool this ptr belongs to is big enough
                if ( size > that->pool->size - sizeof( struct mlt_release_s ) )
                {
                        // Allocate
                        result = mlt_pool_alloc( size );

                        // Copy
                        memcpy( result, ptr, that->pool->size - sizeof( struct mlt_release_s ) );

                        // Release
                        mlt_pool_release( ptr );
                }
                else
                {
                        // Nothing to do
                        result = ptr;
                }
        }
        else
        {
                // Simply allocate
                result = mlt_pool_alloc( size );
        }

        return result;
}

/** Purge unused items in the pool.
 *
 * A form of garbage collection.
 * \public \memberof mlt_pool_s
 */

void mlt_pool_purge( )
{
        int i = 0;

        // For each pool
        for ( i = 0; i < mlt_properties_count( pools ); i ++ )
        {
                // Get the pool
                mlt_pool this = mlt_properties_get_data_at( pools, i, NULL );

                // Pointer to unused memory
                void *release = NULL;

                // Lock the pool
                pthread_mutex_lock( &this->lock );

                // We'll free all unused items now
                while ( ( release = mlt_deque_pop_back( this->stack ) ) != NULL )
                        free( release - sizeof( struct mlt_release_s ) );

                // Unlock the pool
                pthread_mutex_unlock( &this->lock );
        }
}

/** Release the allocated memory.
 *
 * \public \memberof mlt_pool_s
 * \param release an opaque pointer of a block in the pool
 */

void mlt_pool_release( void *release )
{
        // Return to the pool
        pool_return( release );
}

/** Close the pool.
 *
 * \public \memberof mlt_pool_s
 */

void mlt_pool_close( )
{
#ifdef _MLT_POOL_CHECKS_
        // Stats dump on close
        int i = 0;
        for ( i = 0; i < mlt_properties_count( pools ); i ++ )
        {
                mlt_pool pool = mlt_properties_get_data_at( pools, i, NULL );
                if ( pool->count )
                        mlt_log( NULL, MLT_LOG_DEBUG, "%s: size %d allocated %d returned %d %c\n", __FUNCTION__,
                                pool->size, pool->count, mlt_deque_count( pool->stack ),
                                pool->count !=  mlt_deque_count( pool->stack ) ? '*' : ' ' );
        }
#endif

        // Close the properties
        mlt_properties_close( pools );
}