pipewire/spa/plugins/volume/volume.c

/* Spa
 *
 * Copyright © 2018 Wim Taymans
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#include <errno.h>
#include <string.h>
#include <stddef.h>

#include <spa/support/log.h>
#include <spa/utils/list.h>
#include <spa/node/node.h>
#include <spa/node/io.h>
#include <spa/param/audio/format-utils.h>
#include <spa/param/param.h>
#include <spa/pod/filter.h>

#define NAME "volume"

#define DEFAULT_VOLUME 1.0
#define DEFAULT_MUTE false

struct props {
	double volume;
	bool mute;
};

static void reset_props(struct props *props)
{
	props->volume = DEFAULT_VOLUME;
	props->mute = DEFAULT_MUTE;
}

#define MAX_BUFFERS     16

struct buffer {
	uint32_t id;
	struct spa_buffer *outbuf;
	bool outstanding;
	struct spa_meta_header *h;
	void *ptr;
	size_t size;
	struct spa_list link;
};

struct port {
	bool have_format;

	struct spa_port_info info;

	struct buffer buffers[MAX_BUFFERS];
	uint32_t n_buffers;
	struct spa_io_buffers *io;
	struct spa_io_range *range;

	struct spa_list empty;
};

struct impl {
	struct spa_handle handle;
	struct spa_node node;

	struct spa_log *log;

	struct props props;

	const struct spa_node_callbacks *callbacks;
	void *callbacks_data;

	struct spa_audio_info current_format;
	int bpf;

	struct port in_ports[1];
	struct port out_ports[1];

	bool started;
};

#define CHECK_IN_PORT(this,d,p)  ((d) == SPA_DIRECTION_INPUT && (p) == 0)
#define CHECK_OUT_PORT(this,d,p) ((d) == SPA_DIRECTION_OUTPUT && (p) == 0)
#define CHECK_PORT(this,d,p)     ((p) == 0)
#define GET_IN_PORT(this,p)	 (&this->in_ports[p])
#define GET_OUT_PORT(this,p)	 (&this->out_ports[p])
#define GET_PORT(this,d,p)	 (d == SPA_DIRECTION_INPUT ? GET_IN_PORT(this,p) : GET_OUT_PORT(this,p))

static int impl_node_enum_params(struct spa_node *node,
				 uint32_t id, uint32_t start, uint32_t num,
				 const struct spa_pod *filter,
				 spa_result_func_t func, void *data)
{
	struct impl *this;
	struct spa_pod_builder b = { 0 };
	uint8_t buffer[1024];
	struct spa_pod *param;
	struct props *p;
	struct spa_result_node_enum_params result;
	uint32_t count = 0;
	int res;

	spa_return_val_if_fail(node != NULL, -EINVAL);
	spa_return_val_if_fail(num != 0, -EINVAL);
	spa_return_val_if_fail(func != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);
	p = &this->props;

	result.next = start;

      next:
	spa_pod_builder_init(&b, buffer, sizeof(buffer));

	switch (id) {
	case SPA_PARAM_List:
	{
		uint32_t list[] = { SPA_PARAM_PropInfo,
				    SPA_PARAM_Props };

		if (result.next < SPA_N_ELEMENTS(list))
			param = spa_pod_builder_add_object(&b,
				SPA_TYPE_OBJECT_ParamList, id,
				SPA_PARAM_LIST_id, SPA_POD_Id(list[result.next]));
		else
			return 0;
		break;
	}
	case SPA_PARAM_PropInfo:
		switch (result.next) {
		case 0:
			param = spa_pod_builder_add_object(&b,
				SPA_TYPE_OBJECT_PropInfo, id,
				SPA_PROP_INFO_id,   SPA_POD_Id(SPA_PROP_volume),
				SPA_PROP_INFO_name, SPA_POD_String("The volume"),
				SPA_PROP_INFO_type, SPA_POD_CHOICE_RANGE_Float(p->volume, 0.0, 10.0));
			break;
		case 1:
			param = spa_pod_builder_add_object(&b,
				SPA_TYPE_OBJECT_PropInfo, id,
				SPA_PROP_INFO_id,   SPA_POD_Id(SPA_PROP_mute),
				SPA_PROP_INFO_name, SPA_POD_String("Mute"),
				SPA_PROP_INFO_type, SPA_POD_Bool(p->mute));
			break;
		default:
			return 0;
		}
		break;
	case SPA_PARAM_Props:
		switch (result.next) {
		case 0:
			param = spa_pod_builder_add_object(&b,
				SPA_TYPE_OBJECT_Props, id,
				SPA_PROP_volume, SPA_POD_Float(p->volume),
				SPA_PROP_mute,   SPA_POD_Bool(p->mute));
			break;
		default:
			return 0;
		}
		break;
	default:
		return -ENOENT;
	}

	result.next++;

	if (spa_pod_filter(&b, &result.param, param, filter) < 0)
		goto next;

	if ((res = func(data, count, 1, &result)) != 0)
		return res;

	if (++count != num)
		goto next;

	return 0;
}

static int impl_node_set_io(struct spa_node *node, uint32_t id, void *data, size_t size)
{
	return -ENOTSUP;
}

static int impl_node_set_param(struct spa_node *node, uint32_t id, uint32_t flags,
			       const struct spa_pod *param)
{
	struct impl *this;

	spa_return_val_if_fail(node != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	switch (id) {
	case SPA_PARAM_Props:
	{
		struct props *p = &this->props;

		if (param == NULL) {
			reset_props(p);
			return 0;
		}
		spa_pod_parse_object(param,
			SPA_TYPE_OBJECT_Props, NULL,
			SPA_PROP_volume, SPA_POD_OPT_Float(&p->volume),
			SPA_PROP_mute,   SPA_POD_OPT_Bool(&p->mute));
		break;
	}
	default:
		return -ENOENT;
	}

	return 0;
}

static int impl_node_send_command(struct spa_node *node, const struct spa_command *command)
{
	struct impl *this;

	spa_return_val_if_fail(node != NULL, -EINVAL);
	spa_return_val_if_fail(command != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	switch (SPA_NODE_COMMAND_ID(command)) {
	case SPA_NODE_COMMAND_Start:
		this->started = true;
		break;
	case SPA_NODE_COMMAND_Pause:
		this->started = false;
		break;
	default:
		return -ENOTSUP;
	}
	return 0;
}

static void emit_port_info(struct impl *this, enum spa_direction direction, uint32_t id)
{
	struct port *port = GET_PORT(this, direction, id);
	if (this->callbacks && this->callbacks->port_info && port->info.change_mask) {
		this->callbacks->port_info(this->callbacks_data, direction, id, &port->info);
		port->info.change_mask = 0;
	}
}

static int
impl_node_set_callbacks(struct spa_node *node,
			const struct spa_node_callbacks *callbacks,
			void *data)
{
	struct impl *this;

	spa_return_val_if_fail(node != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	this->callbacks = callbacks;
	this->callbacks_data = data;

	emit_port_info(this, SPA_DIRECTION_INPUT, 0);
	emit_port_info(this, SPA_DIRECTION_OUTPUT, 0);

	return 0;
}

static int impl_node_add_port(struct spa_node *node, enum spa_direction direction, uint32_t port_id,
		const struct spa_dict *props)
{
	return -ENOTSUP;
}

static int
impl_node_remove_port(struct spa_node *node, enum spa_direction direction, uint32_t port_id)
{
	return -ENOTSUP;
}

static int port_enum_formats(struct spa_node *node,
			     enum spa_direction direction, uint32_t port_id,
			     uint32_t index,
			     const struct spa_pod *filter,
			     struct spa_pod **param,
			     struct spa_pod_builder *builder)
{
	switch (index) {
	case 0:
		*param = spa_pod_builder_add_object(builder,
			SPA_TYPE_OBJECT_Format, SPA_PARAM_EnumFormat,
			SPA_FORMAT_mediaType,      SPA_POD_Id(SPA_MEDIA_TYPE_audio),
			SPA_FORMAT_mediaSubtype,   SPA_POD_Id(SPA_MEDIA_SUBTYPE_raw),
			SPA_FORMAT_AUDIO_format,   SPA_POD_CHOICE_ENUM_Id(3,
							SPA_AUDIO_FORMAT_S16,
							SPA_AUDIO_FORMAT_S16,
							SPA_AUDIO_FORMAT_S32),
			SPA_FORMAT_AUDIO_rate,     SPA_POD_CHOICE_RANGE_Int(44100, 1, INT32_MAX),
			SPA_FORMAT_AUDIO_channels, SPA_POD_CHOICE_RANGE_Int(2, 1, INT32_MAX));
		break;
	default:
		return 0;
	}
	return 1;
}

static int
impl_node_port_enum_params(struct spa_node *node,
			enum spa_direction direction, uint32_t port_id,
			uint32_t id, uint32_t start, uint32_t num,
			const struct spa_pod *filter,
			spa_result_func_t func, void *data)
{
	struct impl *this;
	struct port *port;
	struct spa_pod_builder b = { 0 };
	uint8_t buffer[1024];
	struct spa_pod *param;
	struct spa_result_node_enum_params result;
	uint32_t count = 0;
	int res;

	spa_return_val_if_fail(node != NULL, -EINVAL);
	spa_return_val_if_fail(num != 0, -EINVAL);
	spa_return_val_if_fail(func != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	spa_return_val_if_fail(CHECK_PORT(this, direction, port_id), -EINVAL);

	port = GET_PORT(this, direction, port_id);

      next:
	spa_pod_builder_init(&b, buffer, sizeof(buffer));

	switch (id) {
	case SPA_PARAM_List:
	{
		uint32_t list[] = { SPA_PARAM_EnumFormat,
				    SPA_PARAM_Format,
				    SPA_PARAM_Buffers,
				    SPA_PARAM_Meta,
				    SPA_PARAM_IO };

		if (result.next < SPA_N_ELEMENTS(list))
			param = spa_pod_builder_add_object(&b,
					SPA_TYPE_OBJECT_ParamList, id,
					SPA_PARAM_LIST_id, SPA_POD_Id(list[result.next]));
		else
			return 0;
		break;
	}
	case SPA_PARAM_EnumFormat:
		if ((res = port_enum_formats(node, direction, port_id,
						result.next, filter, &param, &b)) <= 0)
			return res;
		break;

	case SPA_PARAM_Format:
		if (!port->have_format)
			return -EIO;
		if (result.next > 0)
			return 0;

		param = spa_format_audio_raw_build(&b, id, &this->current_format.info.raw);
		break;

	case SPA_PARAM_Buffers:
		if (!port->have_format)
			return -EIO;
		if (result.next > 0)
			return 0;

		param = spa_pod_builder_add_object(&b,
			SPA_TYPE_OBJECT_ParamBuffers, id,
			SPA_PARAM_BUFFERS_buffers, SPA_POD_CHOICE_RANGE_Int(2, 1, MAX_BUFFERS),
			SPA_PARAM_BUFFERS_blocks,  SPA_POD_Int(1),
			SPA_PARAM_BUFFERS_size,    SPA_POD_CHOICE_RANGE_Int(
							1024 * this->bpf,
							16 * this->bpf,
							INT32_MAX / this->bpf),
			SPA_PARAM_BUFFERS_stride,  SPA_POD_Int(0),
			SPA_PARAM_BUFFERS_align,   SPA_POD_Int(16));
		break;
	case SPA_PARAM_Meta:
		switch (result.next) {
		case 0:
			param = spa_pod_builder_add_object(&b,
				SPA_TYPE_OBJECT_ParamMeta, id,
				SPA_PARAM_META_type, SPA_POD_Id(SPA_META_Header),
				SPA_PARAM_META_size, SPA_POD_Int(sizeof(struct spa_meta_header)));
			break;
		default:
			return 0;
		}
		break;
	case SPA_PARAM_IO:
		switch (result.next) {
		case 0:
			param = spa_pod_builder_add_object(&b,
				SPA_TYPE_OBJECT_ParamIO, id,
				SPA_PARAM_IO_id, SPA_POD_Id(SPA_IO_Buffers),
				SPA_PARAM_IO_size, SPA_POD_Int(sizeof(struct spa_io_buffers)));
			break;
		case 1:
			param = spa_pod_builder_add_object(&b,
				SPA_TYPE_OBJECT_ParamIO, id,
				SPA_PARAM_IO_id, SPA_POD_Id(SPA_IO_Range),
				SPA_PARAM_IO_size, SPA_POD_Int(sizeof(struct spa_io_range)));
			break;
		default:
			return 0;
		}
		break;
	default:
		return -ENOENT;
	}

	result.next++;

	if (spa_pod_filter(&b, &result.param, param, filter) < 0)
		goto next;

	if ((res = func(data, count, 1, &result)) != 0)
		return res;

	if (++count != num)
		goto next;

	return 0;
}

static int clear_buffers(struct impl *this, struct port *port)
{
	if (port->n_buffers > 0) {
		spa_log_info(this->log, NAME " %p: clear buffers", this);
		port->n_buffers = 0;
		spa_list_init(&port->empty);
	}
	return 0;
}

static int port_set_format(struct spa_node *node,
			   enum spa_direction direction, uint32_t port_id,
			   uint32_t flags,
			   const struct spa_pod *format)
{
	struct impl *this = SPA_CONTAINER_OF(node, struct impl, node);
	struct port *port;
	int res;

	port = GET_PORT(this, direction, port_id);

	if (format == NULL) {
		port->have_format = false;
		clear_buffers(this, port);
	} else {
		struct spa_audio_info info = { 0 };

		if ((res = spa_format_parse(format, &info.media_type, &info.media_subtype)) < 0)
			return res;

		if (info.media_type != SPA_MEDIA_TYPE_audio ||
		    info.media_subtype != SPA_MEDIA_SUBTYPE_raw)
			return -EINVAL;

		if (spa_format_audio_raw_parse(format, &info.info.raw) < 0)
			return -EINVAL;

		this->bpf = 2 * info.info.raw.channels;
		this->current_format = info;
		port->have_format = true;
	}

	return 0;
}

static int
impl_node_port_set_param(struct spa_node *node,
			 enum spa_direction direction, uint32_t port_id,
			 uint32_t id, uint32_t flags,
			 const struct spa_pod *param)
{
	spa_return_val_if_fail(node != NULL, -EINVAL);

	spa_return_val_if_fail(CHECK_PORT(node, direction, port_id), -EINVAL);

	if (id == SPA_PARAM_Format) {
		return port_set_format(node, direction, port_id, flags, param);
	}
	else
		return -ENOENT;
}

static int
impl_node_port_use_buffers(struct spa_node *node,
			   enum spa_direction direction,
			   uint32_t port_id,
			   struct spa_buffer **buffers,
			   uint32_t n_buffers)
{
	struct impl *this;
	struct port *port;
	uint32_t i;

	spa_return_val_if_fail(node != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	spa_return_val_if_fail(CHECK_PORT(this, direction, port_id), -EINVAL);

	port = GET_PORT(this, direction, port_id);

	if (!port->have_format)
		return -EIO;

	clear_buffers(this, port);

	for (i = 0; i < n_buffers; i++) {
		struct buffer *b;
		struct spa_data *d = buffers[i]->datas;

		b = &port->buffers[i];
		b->id = i;
		b->outbuf = buffers[i];
		b->outstanding = direction == SPA_DIRECTION_INPUT;
		b->h = spa_buffer_find_meta_data(buffers[i], SPA_META_Header, sizeof(*b->h));

		if ((d[0].type == SPA_DATA_MemPtr ||
		     d[0].type == SPA_DATA_MemFd ||
		     d[0].type == SPA_DATA_DmaBuf) && d[0].data != NULL) {
			b->ptr = d[0].data;
			b->size = d[0].maxsize;
		} else {
			spa_log_error(this->log, NAME " %p: invalid memory on buffer %p", this,
				      buffers[i]);
			return -EINVAL;
		}
		if (!b->outstanding)
			spa_list_append(&port->empty, &b->link);
	}
	port->n_buffers = n_buffers;

	return 0;
}

static int
impl_node_port_alloc_buffers(struct spa_node *node,
			     enum spa_direction direction,
			     uint32_t port_id,
			     struct spa_pod **params,
			     uint32_t n_params,
			     struct spa_buffer **buffers,
			     uint32_t *n_buffers)
{
	return -ENOTSUP;
}

static int
impl_node_port_set_io(struct spa_node *node,
		      enum spa_direction direction,
		      uint32_t port_id,
		      uint32_t id,
		      void *data, size_t size)
{
	struct impl *this;
	struct port *port;

	spa_return_val_if_fail(node != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	spa_return_val_if_fail(CHECK_PORT(this, direction, port_id), -EINVAL);

	port = GET_PORT(this, direction, port_id);

	switch (id) {
	case SPA_IO_Buffers:
		port->io = data;
		break;
	case SPA_IO_Range:
		port->range = data;
		break;
	default:
		return -ENOENT;
	}
	return 0;
}

static void recycle_buffer(struct impl *this, uint32_t id)
{
	struct port *port = GET_OUT_PORT(this, 0);
	struct buffer *b = &port->buffers[id];

	if (!b->outstanding) {
		spa_log_warn(this->log, NAME " %p: buffer %d not outstanding", this, id);
		return;
	}

	spa_list_append(&port->empty, &b->link);
	b->outstanding = false;
	spa_log_trace(this->log, NAME " %p: recycle buffer %d", this, id);
}

static int impl_node_port_reuse_buffer(struct spa_node *node, uint32_t port_id, uint32_t buffer_id)
{
	struct impl *this;
	struct port *port;

	spa_return_val_if_fail(node != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	spa_return_val_if_fail(CHECK_PORT(this, SPA_DIRECTION_OUTPUT, port_id),
			       -EINVAL);

	port = GET_OUT_PORT(this, port_id);

	if (buffer_id >= port->n_buffers)
		return -EINVAL;

	recycle_buffer(this, buffer_id);

	return 0;
}

static struct buffer *find_free_buffer(struct impl *this, struct port *port)
{
	struct buffer *b;

	if (spa_list_is_empty(&port->empty))
		return NULL;

	b = spa_list_first(&port->empty, struct buffer, link);
	spa_list_remove(&b->link);
	b->outstanding = true;

	return b;
}

static void do_volume(struct impl *this, struct spa_buffer *dbuf, struct spa_buffer *sbuf)
{
	uint32_t i, n_samples, n_bytes;
	struct spa_data *sd, *dd;
	int16_t *src, *dst;
	double volume;
	uint32_t written, towrite, savail, davail;
	uint32_t sindex, dindex;

	volume = this->props.volume;

	sd = sbuf->datas;
	dd = dbuf->datas;

	savail = SPA_MIN(sd[0].chunk->size, sd[0].maxsize);
	sindex = sd[0].chunk->offset;
	davail = 0;
	dindex = 0;
	davail = dd[0].maxsize - davail;

	towrite = SPA_MIN(savail, davail);
	written = 0;

	while (written < towrite) {
		uint32_t soffset = sindex % sd[0].maxsize;
		uint32_t doffset = dindex % dd[0].maxsize;

		src = SPA_MEMBER(sd[0].data, soffset, int16_t);
		dst = SPA_MEMBER(dd[0].data, doffset, int16_t);

		n_bytes = SPA_MIN(towrite, sd[0].maxsize - soffset);
		n_bytes = SPA_MIN(n_bytes, dd[0].maxsize - doffset);

		n_samples = n_bytes / sizeof(int16_t);
		for (i = 0; i < n_samples; i++)
			dst[i] = src[i] * volume;

		sindex += n_bytes;
		dindex += n_bytes;
		written += n_bytes;
	}
	dd[0].chunk->offset = 0;
	dd[0].chunk->size = written;
	dd[0].chunk->stride = 0;
}

static int impl_node_process(struct spa_node *node)
{
	struct impl *this;
	struct port *in_port, *out_port;
	struct spa_io_buffers *input, *output;
	struct buffer *dbuf, *sbuf;

	spa_return_val_if_fail(node != NULL, -EINVAL);

	this = SPA_CONTAINER_OF(node, struct impl, node);

	out_port = GET_OUT_PORT(this, 0);
	output = out_port->io;
	spa_return_val_if_fail(output != NULL, -EIO);

	if (output->status == SPA_STATUS_HAVE_BUFFER)
		return SPA_STATUS_HAVE_BUFFER;

	/* recycle */
	if (output->buffer_id < out_port->n_buffers) {
		recycle_buffer(this, output->buffer_id);
		output->buffer_id = SPA_ID_INVALID;
	}

	in_port = GET_IN_PORT(this, 0);
	input = in_port->io;
	spa_return_val_if_fail(input != NULL, -EIO);

	if (input->status != SPA_STATUS_HAVE_BUFFER)
		return SPA_STATUS_NEED_BUFFER;

	if (input->buffer_id >= in_port->n_buffers) {
		input->status = -EINVAL;
		return -EINVAL;
	}

	if ((dbuf = find_free_buffer(this, out_port)) == NULL) {
                spa_log_error(this->log, NAME " %p: out of buffers", this);
		return -EPIPE;
	}

	sbuf = &in_port->buffers[input->buffer_id];

	spa_log_trace(this->log, NAME " %p: do volume %d -> %d", this, sbuf->id, dbuf->id);
	do_volume(this, dbuf->outbuf, sbuf->outbuf);

	output->buffer_id = dbuf->id;
	output->status = SPA_STATUS_HAVE_BUFFER;

	if (in_port->range && out_port->range)
		*in_port->range = *out_port->range;
	input->status = SPA_STATUS_NEED_BUFFER;

	return SPA_STATUS_HAVE_BUFFER;
}

static const struct spa_node impl_node = {
	SPA_VERSION_NODE,
	.enum_params = impl_node_enum_params,
	.set_param = impl_node_set_param,
	.set_io = impl_node_set_io,
	.send_command = impl_node_send_command,
	.set_callbacks = impl_node_set_callbacks,
	.add_port = impl_node_add_port,
	.remove_port = impl_node_remove_port,
	.port_enum_params = impl_node_port_enum_params,
	.port_set_param = impl_node_port_set_param,
	.port_use_buffers = impl_node_port_use_buffers,
	.port_alloc_buffers = impl_node_port_alloc_buffers,
	.port_set_io = impl_node_port_set_io,
	.port_reuse_buffer = impl_node_port_reuse_buffer,
	.process = impl_node_process,
};

static int impl_get_interface(struct spa_handle *handle, uint32_t type, void **interface)
{
	struct impl *this;

	spa_return_val_if_fail(handle != NULL, -EINVAL);
	spa_return_val_if_fail(interface != NULL, -EINVAL);

	this = (struct impl *) handle;

	if (type == SPA_TYPE_INTERFACE_Node)
		*interface = &this->node;
	else
		return -ENOENT;

	return 0;
}

static int impl_clear(struct spa_handle *handle)
{
	return 0;
}

static size_t
impl_get_size(const struct spa_handle_factory *factory,
	      const struct spa_dict *params)
{
	return sizeof(struct impl);
}

static int
impl_init(const struct spa_handle_factory *factory,
	  struct spa_handle *handle,
	  const struct spa_dict *info,
	  const struct spa_support *support,
	  uint32_t n_support)
{
	struct impl *this;
	struct port *port;
	uint32_t i;

	spa_return_val_if_fail(factory != NULL, -EINVAL);
	spa_return_val_if_fail(handle != NULL, -EINVAL);

	handle->get_interface = impl_get_interface;
	handle->clear = impl_clear;

	this = (struct impl *) handle;

	for (i = 0; i < n_support; i++) {
		if (support[i].type == SPA_TYPE_INTERFACE_Log)
			this->log = support[i].data;
	}

	this->node = impl_node;
	reset_props(&this->props);

	port = GET_IN_PORT(this, 0);
	port->info = SPA_PORT_INFO_INIT();
	port->info.change_mask = SPA_PORT_CHANGE_MASK_FLAGS;
	port->info.flags = SPA_PORT_FLAG_CAN_USE_BUFFERS |
	    SPA_PORT_FLAG_IN_PLACE;
	spa_list_init(&port->empty);

	port = GET_OUT_PORT(this, 0);
	port->info = SPA_PORT_INFO_INIT();
	port->info.change_mask = SPA_PORT_CHANGE_MASK_FLAGS;
	port->info.flags = SPA_PORT_FLAG_CAN_USE_BUFFERS |
	    SPA_PORT_FLAG_NO_REF;
	spa_list_init(&port->empty);

	return 0;
}

static const struct spa_interface_info impl_interfaces[] = {
	{SPA_TYPE_INTERFACE_Node,},
};

static int
impl_enum_interface_info(const struct spa_handle_factory *factory,
			 const struct spa_interface_info **info,
			 uint32_t *index)
{
	spa_return_val_if_fail(factory != NULL, -EINVAL);
	spa_return_val_if_fail(info != NULL, -EINVAL);
	spa_return_val_if_fail(index != NULL, -EINVAL);

	switch (*index) {
	case 0:
		*info = &impl_interfaces[*index];
		break;
	default:
		return 0;
	}
	(*index)++;
	return 1;
}

const struct spa_handle_factory spa_volume_factory = {
	SPA_VERSION_HANDLE_FACTORY,
	NAME,
	NULL,
	impl_get_size,
	impl_init,
	impl_enum_interface_info,
};