mlt_service.c

/**
 * \file mlt_service.c
 * \brief interface definition for all service classes
 * \see mlt_service_s
 *
 * Copyright (C) 2003-2022 Meltytech, LLC
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "mlt_service.h"
#include "mlt_cache.h"
#include "mlt_factory.h"
#include "mlt_filter.h"
#include "mlt_frame.h"
#include "mlt_log.h"
#include "mlt_producer.h"

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

/*  IMPORTANT NOTES

  	The base service implements a null frame producing service - as such,
	it is functional without extension and will produce test cards frames
	and PAL sized audio frames.

	PLEASE DO NOT CHANGE THIS BEHAVIOUR!!! OVERRIDE THE METHODS THAT
	CONTROL THIS IN EXTENDING CLASSES.
*/

/** \brief private service definition */

typedef struct
{
    int size;
    int count;
    mlt_service *in;
    mlt_service out;
    int filter_count;
    int filter_size;
    mlt_filter *filters;
    pthread_mutex_t mutex;
} mlt_service_base;

/* Private methods
 */

static void mlt_service_disconnect(mlt_service self);
static void mlt_service_connect(mlt_service self, mlt_service that);
static int service_get_frame(mlt_service self, mlt_frame_ptr frame, int index);

/** Initialize a service.
 *
 * \public \memberof mlt_service_s
 * \param self the service structure to initialize
 * \param child pointer to the child object for the subclass
 * \return true if there was an error
 */

int mlt_service_init(mlt_service self, void *child)
{
    int error = 0;

    // Initialise everything to NULL
    memset(self, 0, sizeof(struct mlt_service_s));

    // Assign the child
    self->child = child;

    // Generate local space
    self->local = calloc(1, sizeof(mlt_service_base));

    // Associate the methods
    self->get_frame = service_get_frame;

    // Initialise the properties
    error = mlt_properties_init(&self->parent, self);
    if (error == 0) {
        self->parent.close = (mlt_destructor) mlt_service_close;
        self->parent.close_object = self;

        mlt_events_init(&self->parent);
        mlt_events_register(&self->parent, "service-changed");
        mlt_events_register(&self->parent, "property-changed");
        pthread_mutex_init(&((mlt_service_base *) self->local)->mutex, NULL);
    }

    return error;
}

/** Acquire a mutual exclusion lock on this service.
 *
 * \public \memberof mlt_service_s
 * \param self the service to lock
 */

void mlt_service_lock(mlt_service self)
{
    if (self != NULL)
        pthread_mutex_lock(&((mlt_service_base *) self->local)->mutex);
}

/** Release a mutual exclusion lock on this service.
 *
 * \public \memberof mlt_service_s
 * \param self the service to unlock
 */

void mlt_service_unlock(mlt_service self)
{
    if (self != NULL)
        pthread_mutex_unlock(&((mlt_service_base *) self->local)->mutex);
}

/** Identify the subclass of the service.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the subclass
 */

mlt_service_type mlt_service_identify(mlt_service self)
{
    mlt_service_type type = mlt_service_invalid_type;
    if (self != NULL) {
        mlt_properties properties = MLT_SERVICE_PROPERTIES(self);
        char *mlt_type = mlt_properties_get(properties, "mlt_type");
        char *resource = mlt_properties_get(properties, "resource");
        if (mlt_type == NULL)
            type = mlt_service_unknown_type;
        else if (resource != NULL && !strcmp(resource, "<playlist>"))
            type = mlt_service_playlist_type;
        else if (resource != NULL && !strcmp(resource, "<tractor>"))
            type = mlt_service_tractor_type;
        else if (resource != NULL && !strcmp(resource, "<multitrack>"))
            type = mlt_service_multitrack_type;
        else if (!strcmp(mlt_type, "mlt_producer"))
            type = mlt_service_producer_type;
        else if (!strcmp(mlt_type, "producer"))
            type = mlt_service_producer_type;
        else if (!strcmp(mlt_type, "filter"))
            type = mlt_service_filter_type;
        else if (!strcmp(mlt_type, "transition"))
            type = mlt_service_transition_type;
        else if (!strcmp(mlt_type, "chain"))
            type = mlt_service_chain_type;
        else if (!strcmp(mlt_type, "consumer"))
            type = mlt_service_consumer_type;
        else if (!strcmp(mlt_type, "link"))
            type = mlt_service_link_type;
        else
            type = mlt_service_unknown_type;
    }
    return type;
}

/** Connect a producer to the service.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param producer a producer
 * \param index which of potentially multiple producers to this service (0 based)
 * \return 0 for success, -1 for error, or 3 if \p producer is already connected to \p self
 */

int mlt_service_connect_producer(mlt_service self, mlt_service producer, int index)
{
    int i = 0;

    // Get the service base
    mlt_service_base *base = self->local;

    // Special case 'track' index - only works for last filter(s) in a particular chain
    // but allows a filter to apply to the output frame regardless of which track it comes from
    if (index == -1)
        index = 0;

    // Check if the producer is already registered with this service
    for (i = 0; i < base->count; i++)
        if (base->in[i] == producer)
            return 3;

    // Allocate space
    if (index >= base->size) {
        int new_size = base->size + index + 10;
        base->in = realloc(base->in, new_size * sizeof(mlt_service));
        if (base->in != NULL) {
            for (i = base->size; i < new_size; i++)
                base->in[i] = NULL;
            base->size = new_size;
        }
    }

    // If we have space, assign the input
    if (producer != NULL && base->in != NULL && index >= 0 && index < base->size) {
        // Get the current service
        mlt_service current = (index < base->count) ? base->in[index] : NULL;

        // Increment the reference count on this producer
        mlt_properties_inc_ref(MLT_SERVICE_PROPERTIES(producer));

        // Now we disconnect the producer service from its consumer
        mlt_service_disconnect(producer);

        // Add the service to index specified
        base->in[index] = producer;

        // Determine the number of active tracks
        if (index >= base->count)
            base->count = index + 1;

        // Now we connect the producer to its connected consumer
        mlt_service_connect(producer, self);

        // Close the current service
        mlt_service_close(current);

        // Inform caller that all went well
        return 0;
    } else {
        return -1;
    }
}

/** Insert a producer connected to the service.
 *
 * mlt_service_connect_producer() appends or overwrites a producer at input
 * \p index whereas this function inserts pushing all of the inputs down by
 * 1 in the list of inputs.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param producer a producer
 * \param index which of potentially multiple producers to this service (0 based)
 * \return 0 for success, -1 for error, or 3 if \p producer is already connected to \p self
 */

int mlt_service_insert_producer(mlt_service self, mlt_service producer, int index)
{
    // Get the service base
    mlt_service_base *base = self->local;

    if (index >= base->count)
        return mlt_service_connect_producer(self, producer, index);

    int i = 0;

    // Special case 'track' index - only works for last filter(s) in a particular chain
    // but allows a filter to apply to the output frame regardless of which track it comes from
    if (index == -1)
        index = 0;

    // Check if the producer is already registered with this service.
    for (i = 0; i < base->count; i++)
        if (base->in[i] == producer)
            return 3;

    // Allocate space if needed.
    if (base->count + 1 > base->size) {
        int new_size = base->size + 10;
        base->in = realloc(base->in, new_size * sizeof(mlt_service));
        if (base->in != NULL) {
            memset(&base->in[base->size], 0, new_size - base->size);
            base->size = new_size;
        }
    }

    // If we have space, assign the input
    if (base->in && index >= 0 && index < base->size) {
        // Increment the reference count on this producer.
        if (producer != NULL)
            mlt_properties_inc_ref(MLT_SERVICE_PROPERTIES(producer));

        // Disconnect the producer from its consumer.
        mlt_service_disconnect(producer);

        // Make room in the list for the producer.
        memmove(&base->in[index + 1], &base->in[index], (base->count - index) * sizeof(mlt_service));

        // Add the service to index specified.
        base->in[index] = producer;

        // Increase the number of active tracks.
        base->count++;

        // Connect the producer to its connected consumer.
        mlt_service_connect(producer, self);

        // Inform caller that all went well
        return 0;
    } else {
        return -1;
    }
}

/** Remove the N-th producer.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param index which producer to remove (0-based)
 * \return true if there was an error
 */

int mlt_service_disconnect_producer(mlt_service self, int index)
{
    mlt_service_base *base = self->local;

    if (base->in && index >= 0 && index < base->count) {
        mlt_service current = base->in[index];

        if (current) {
            // Close the current producer.
            mlt_service_disconnect(current);
            mlt_service_close(current);
            base->in[index] = NULL;

            // Contract the list of producers.
            for (; index + 1 < base->count; index++)
                base->in[index] = base->in[index + 1];
            base->count--;
            return 0;
        }
    }
    return -1;
}

/** Remove the all the attached producers
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the number of successfully disconnected producers
 */

int mlt_service_disconnect_all_producers(mlt_service self)
{
    int disconnected = 0, i = 0;
    mlt_service_base *base = self->local;

    if (base->in) {
        for (i = 0; i < base->count; i++) {
            mlt_service current = base->in[i];
            if (current) {
                mlt_service_close(current);
                disconnected++;
            }
            base->in[i] = NULL;
        }
        base->count = 0;
    }

    return disconnected;
}

/** Disconnect a service from its consumer.
 *
 * \private \memberof mlt_service_s
 * \param self a service
 */

static void mlt_service_disconnect(mlt_service self)
{
    if (self != NULL) {
        // Get the service base
        mlt_service_base *base = self->local;

        // Disconnect
        base->out = NULL;
    }
}

/** Obtain the consumer a service is connected to.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the consumer
 */

mlt_service mlt_service_consumer(mlt_service self)
{
    if (self) {
        // Get the service base
        mlt_service_base *base = self->local;

        // Return the connected consumer
        return base->out;
    } else
        return self;
}

/** Obtain the producer a service is connected to.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the last-most producer
 */

mlt_service mlt_service_producer(mlt_service self)
{
    if (self) {
        // Get the service base
        mlt_service_base *base = self->local;

        // Return the connected producer
        return base->count > 0 ? base->in[base->count - 1] : NULL;
    } else
        return self;
}

/** Get the N-th connected producer.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param index which of potentially multiple producers to this service (0 based)
 * \return the N-th producer
 */

mlt_service mlt_service_peek_producer(mlt_service self, int index)
{
    mlt_service producer = NULL;

    // Get the service base
    mlt_service_base *base = self->local;

    if (base->in != NULL && index < base->count)
        producer = base->in[index];

    return producer;
}

/** Associate a service to a consumer.
 *
 * Overwrites connection to any existing consumer.
 * \private \memberof mlt_service_s
 * \param self a service
 * \param that a consumer
 */

static void mlt_service_connect(mlt_service self, mlt_service that)
{
    if (self != NULL) {
        // Get the service base
        mlt_service_base *base = self->local;

        // There's a bit more required here...
        base->out = that;
    }
}

/** Get the first connected producer.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the first producer
 */

mlt_service mlt_service_get_producer(mlt_service self)
{
    mlt_service producer = NULL;

    // Get the service base
    mlt_service_base *base = self->local;

    if (base->in != NULL)
        producer = base->in[0];

    return producer;
}

/** Default implementation of the get_frame virtual function.
 *
 * \private \memberof mlt_service_s
 * \param self a service
 * \param[out] frame a frame by reference
 * \param index as determined by the producer
 * \return false
 */

static int service_get_frame(mlt_service self, mlt_frame_ptr frame, int index)
{
    mlt_service_base *base = self->local;
    if (index < base->count) {
        mlt_service producer = base->in[index];
        if (producer != NULL)
            return mlt_service_get_frame(producer, frame, index);
    }
    *frame = mlt_frame_init(self);
    return 0;
}

/** Return the properties object.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the properties
 */

mlt_properties mlt_service_properties(mlt_service self)
{
    return self != NULL ? &self->parent : NULL;
}

/** Recursively apply attached filters.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param frame a frame
 * \param index used to track depth of recursion, top caller should supply 0
 */

void mlt_service_apply_filters(mlt_service self, mlt_frame frame, int index)
{
    if (!self)
        return;

    int i;
    mlt_properties frame_properties = MLT_FRAME_PROPERTIES(frame);
    mlt_properties service_properties = MLT_SERVICE_PROPERTIES(self);
    mlt_service_base *base = self->local;
    mlt_position position = mlt_frame_get_position(frame);
    mlt_position self_in = mlt_properties_get_position(service_properties, "in");
    mlt_position self_out = mlt_properties_get_position(service_properties, "out");

    if (index == 0 || mlt_properties_get_int(service_properties, "_filter_private") == 0) {
        // Process the frame with the attached filters
        for (i = 0; i < base->filter_count; i++) {
            if (base->filters[i] != NULL) {
                mlt_position in = mlt_filter_get_in(base->filters[i]);
                mlt_position out = mlt_filter_get_out(base->filters[i]);
                int disable = mlt_properties_get_int(MLT_FILTER_PROPERTIES(base->filters[i]),
                                                     "disable");
                if (!disable
                    && ((in == 0 && out == 0)
                        || (position >= in && (position <= out || out == 0)))) {
                    mlt_properties_set_position(frame_properties, "in", in == 0 ? self_in : in);
                    mlt_properties_set_position(frame_properties, "out", out == 0 ? self_out : out);
                    mlt_filter_process(base->filters[i], frame);
                    mlt_service_apply_filters(MLT_FILTER_SERVICE(base->filters[i]),
                                              frame,
                                              index + 1);
                }
            }
        }
    }
}

/** Obtain a frame.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param[out] frame a frame by reference
 * \param index as determined by the producer
 * \return true if there was an error
 */

int mlt_service_get_frame(mlt_service self, mlt_frame_ptr frame, int index)
{
    int result = 0;

    // Lock the service
    mlt_service_lock(self);

    // Ensure that the frame is NULL
    *frame = NULL;

    // Only process if we have a valid service
    if (self != NULL && self->get_frame != NULL) {
        mlt_properties properties = MLT_SERVICE_PROPERTIES(self);
        mlt_position in = mlt_properties_get_position(properties, "in");
        mlt_position out = mlt_properties_get_position(properties, "out");
        mlt_position position = -1;
        if (mlt_service_identify(self) == mlt_service_producer_type
            || mlt_service_identify(self) == mlt_service_chain_type) {
            position = mlt_producer_position(MLT_PRODUCER(self));
        }

        result = self->get_frame(self, frame, index);

        if (result == 0) {
            mlt_properties_inc_ref(properties);
            properties = MLT_FRAME_PROPERTIES(*frame);

            if (in >= 0 && out > 0) {
                mlt_properties_set_position(properties, "in", in);
                mlt_properties_set_position(properties, "out", out);
            }
            mlt_service_apply_filters(self, *frame, 1);
            mlt_deque_push_back(MLT_FRAME_SERVICE_STACK(*frame), self);

            if (position > -1
                && mlt_properties_get_int(MLT_SERVICE_PROPERTIES(self), "_need_previous_next")) {
                // Save the new position from self->get_frame
                mlt_position new_position = mlt_producer_position(MLT_PRODUCER(self));

                // Get the preceding frame, unfiltered
                mlt_frame previous_frame;
                mlt_producer_seek(MLT_PRODUCER(self), position - 1);
                result = self->get_frame(self, &previous_frame, index);
                if (!result)
                    mlt_properties_set_data(properties,
                                            "previous frame",
                                            previous_frame,
                                            0,
                                            (mlt_destructor) mlt_frame_close,
                                            NULL);

                // Get the following frame, unfiltered
                mlt_frame next_frame;
                mlt_producer_seek(MLT_PRODUCER(self), position + 1);
                result = self->get_frame(self, &next_frame, index);
                if (!result) {
                    mlt_properties_set_data(properties,
                                            "next frame",
                                            next_frame,
                                            0,
                                            (mlt_destructor) mlt_frame_close,
                                            NULL);
                }

                // Restore the new position
                mlt_producer_seek(MLT_PRODUCER(self), new_position);
            }
        }
    }

    // Make sure we return a frame
    if (*frame == NULL)
        *frame = mlt_frame_init(self);

    // Unlock the service
    mlt_service_unlock(self);

    return result;
}

/** The service-changed event handler.
 *
 * \private \memberof mlt_service_s
 * \param owner ignored
 * \param self the service on which the "service-changed" event is fired
 */

static void mlt_service_filter_changed(mlt_service owner, mlt_service self)
{
    mlt_events_fire(MLT_SERVICE_PROPERTIES(self), "service-changed", mlt_event_data_none());
}

/** The property-changed event handler.
 *
 * \private \memberof mlt_service_s
 * \param owner ignored
 * \param self the service on which the "property-changed" event is fired
 * \param name the name of the property that changed
 */

static void mlt_service_filter_property_changed(mlt_service owner,
                                                mlt_service self,
                                                mlt_event_data event_data)
{
    mlt_events_fire(MLT_SERVICE_PROPERTIES(self), "property-changed", event_data);
}

/** Attach a filter.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param filter the filter to attach
 * \return true if there was an error
 */

int mlt_service_attach(mlt_service self, mlt_filter filter)
{
    int error = self == NULL || filter == NULL;
    if (error == 0) {
        int i = 0;
        mlt_properties properties = MLT_SERVICE_PROPERTIES(self);
        mlt_service_base *base = self->local;

        for (i = 0; error == 0 && i < base->filter_count; i++)
            if (base->filters[i] == filter)
                error = 1;

        if (error == 0) {
            if (base->filter_count == base->filter_size) {
                base->filter_size += 10;
                base->filters = realloc(base->filters, base->filter_size * sizeof(mlt_filter));
            }

            if (base->filters != NULL) {
                mlt_properties props = MLT_FILTER_PROPERTIES(filter);
                mlt_properties_inc_ref(MLT_FILTER_PROPERTIES(filter));
                base->filters[base->filter_count++] = filter;
                mlt_properties_set_data(props, "service", self, 0, NULL, NULL);
                mlt_events_fire(properties, "service-changed", mlt_event_data_none());
                mlt_events_fire(props, "service-changed", mlt_event_data_none());
                mlt_service cp = mlt_properties_get_data(properties, "_cut_parent", NULL);
                if (cp)
                    mlt_events_fire(MLT_SERVICE_PROPERTIES(cp),
                                    "service-changed",
                                    mlt_event_data_none());
                mlt_events_listen(props,
                                  self,
                                  "service-changed",
                                  (mlt_listener) mlt_service_filter_changed);
                mlt_events_listen(props,
                                  self,
                                  "property-changed",
                                  (mlt_listener) mlt_service_filter_property_changed);
            } else {
                error = 2;
            }
        }
    }
    return error;
}

/** Detach a filter.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param filter the filter to detach
 * \return true if there was an error
 */

int mlt_service_detach(mlt_service self, mlt_filter filter)
{
    int error = self == NULL || filter == NULL;
    if (error == 0) {
        int i = 0;
        mlt_service_base *base = self->local;
        mlt_properties properties = MLT_SERVICE_PROPERTIES(self);

        for (i = 0; i < base->filter_count; i++)
            if (base->filters[i] == filter)
                break;

        if (i < base->filter_count) {
            base->filters[i] = NULL;
            for (i++; i < base->filter_count; i++)
                base->filters[i - 1] = base->filters[i];
            base->filter_count--;
            mlt_events_disconnect(MLT_FILTER_PROPERTIES(filter), self);
            mlt_filter_close(filter);
            mlt_events_fire(properties, "service-changed", mlt_event_data_none());
        }
    }
    return error;
}

/** Get the number of filters attached.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the number of attached filters or -1 if there was an error
 */

int mlt_service_filter_count(mlt_service self)
{
    int result = -1;
    if (self) {
        mlt_service_base *base = self->local;
        result = base->filter_count;
    }
    return result;
}

/** Reorder the attached filters.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param from the current index value of the filter to move
 * \param to the new index value for the filter specified in \p from
 * \return true if there was an error
 */

int mlt_service_move_filter(mlt_service self, int from, int to)
{
    int error = -1;
    if (self) {
        mlt_service_base *base = self->local;
        if (from < 0)
            from = 0;
        if (from >= base->filter_count)
            from = base->filter_count - 1;
        if (to < 0)
            to = 0;
        if (to >= base->filter_count)
            to = base->filter_count - 1;
        if (from != to && base->filter_count > 1) {
            mlt_filter filter = base->filters[from];
            int i;
            if (from > to) {
                for (i = from; i > to; i--)
                    base->filters[i] = base->filters[i - 1];
            } else {
                for (i = from; i < to; i++)
                    base->filters[i] = base->filters[i + 1];
            }
            base->filters[to] = filter;
            mlt_events_fire(MLT_SERVICE_PROPERTIES(self), "service-changed", mlt_event_data_none());
            error = 0;
        }
    }
    return error;
}

/** Retrieve an attached filter.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param index which one of potentially multiple filters
 * \return the filter or null if there was an error
 */

mlt_filter mlt_service_filter(mlt_service self, int index)
{
    mlt_filter filter = NULL;
    if (self != NULL) {
        mlt_service_base *base = self->local;
        if (index >= 0 && index < base->filter_count)
            filter = base->filters[index];
    }
    return filter;
}

/** Retrieve the profile.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \return the profile
 */

mlt_profile mlt_service_profile(mlt_service self)
{
    return self ? mlt_properties_get_data(MLT_SERVICE_PROPERTIES(self), "_profile", NULL) : NULL;
}

/** Set the profile for a service.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param profile the profile to set onto the service
 */

void mlt_service_set_profile(mlt_service self, mlt_profile profile)
{
    mlt_properties_set_data(MLT_SERVICE_PROPERTIES(self), "_profile", profile, 0, NULL, NULL);
}

/** Destroy a service.
 *
 * \public \memberof mlt_service_s
 * \param self the service to destroy
 */

void mlt_service_close(mlt_service self)
{
    if (self != NULL && mlt_properties_dec_ref(MLT_SERVICE_PROPERTIES(self)) <= 0) {
        if (self->close != NULL) {
            self->close(self->close_object);
        } else {
            mlt_service_base *base = self->local;
            int i = 0;
            int count = base->filter_count;
            mlt_events_block(MLT_SERVICE_PROPERTIES(self), self);
            while (count--)
                mlt_service_detach(self, base->filters[0]);
            free(base->filters);
            for (i = 0; i < base->count; i++)
                if (base->in[i] != NULL)
                    mlt_service_close(base->in[i]);
            self->parent.close = NULL;
            free(base->in);
            pthread_mutex_destroy(&base->mutex);
            free(base);
            mlt_properties_close(&self->parent);
        }
    }
}

/** Release a service's cache items.
 *
 * \private \memberof mlt_service_s
 * \param self a service
 */

void mlt_service_cache_purge(mlt_service self)
{
    mlt_properties caches = mlt_properties_get_data(mlt_global_properties(), "caches", NULL);

    if (caches) {
        int i = mlt_properties_count(caches);
        while (i--) {
            mlt_cache_purge(mlt_properties_get_data_at(caches, i, NULL), self);
            mlt_properties_set_data(mlt_global_properties(),
                                    mlt_properties_get_name(caches, i),
                                    NULL,
                                    0,
                                    NULL,
                                    NULL);
        }
    }
}

/** Lookup the cache object for a service.
 *
 * \private \memberof mlt_service_s
 * \param self a service
 * \param name a name for the object
 * \return a cache
 */

static mlt_cache get_cache(mlt_service self, const char *name)
{
    mlt_cache result = NULL;
    mlt_properties caches = mlt_properties_get_data(mlt_global_properties(), "caches", NULL);

    if (!caches) {
        caches = mlt_properties_new();
        mlt_properties_set_data(mlt_global_properties(),
                                "caches",
                                caches,
                                0,
                                (mlt_destructor) mlt_properties_close,
                                NULL);
    }
    if (caches) {
        result = mlt_properties_get_data(caches, name, NULL);
        if (!result) {
            result = mlt_cache_init();
            mlt_properties_set_data(caches, name, result, 0, (mlt_destructor) mlt_cache_close, NULL);
        }
    }

    return result;
}

/** Put an object into a service's cache.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param name a name for the object that is unique to the service class, but not to the instance
 * \param data an opaque pointer to the object to put into the cache
 * \param size the number of bytes pointed to by data
 * \param destructor a function that releases the data
 */

void mlt_service_cache_put(
    mlt_service self, const char *name, void *data, int size, mlt_destructor destructor)
{
    mlt_log(self, MLT_LOG_DEBUG, "%s: name %s object %p data %p\n", __FUNCTION__, name, self, data);
    mlt_cache cache = get_cache(self, name);

    if (cache)
        mlt_cache_put(cache, self, data, size, destructor);
}

/** Get an object from a service's cache.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param name a name for the object that is unique to the service class, but not to the instance
 * \return a cache item or NULL if an object is not found
 * \see mlt_cache_item_data
 */

mlt_cache_item mlt_service_cache_get(mlt_service self, const char *name)
{
    mlt_log(self, MLT_LOG_DEBUG, "%s: name %s object %p\n", __FUNCTION__, name, self);
    mlt_cache_item result = NULL;
    mlt_cache cache = get_cache(self, name);

    if (cache)
        result = mlt_cache_get(cache, self);

    return result;
}

/** Set the number of items to cache for the named cache.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param name a name for the object that is unique to the service class, but not to the instance
 * \param size the number of items to cache
 */

void mlt_service_cache_set_size(mlt_service self, const char *name, int size)
{
    mlt_cache cache = get_cache(self, name);
    if (cache)
        mlt_cache_set_size(cache, size);
}

/** Get the current maximum size of the named cache.
 *
 * \public \memberof mlt_service_s
 * \param self a service
 * \param name a name for the object that is unique to the service class, but not to the instance
 * \return the current maximum number of items to cache or zero if there is an error
 */

int mlt_service_cache_get_size(mlt_service self, const char *name)
{
    mlt_cache cache = get_cache(self, name);
    if (cache)
        return mlt_cache_get_size(cache);
    else
        return 0;
}