text: /* 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/plugin.h>
  #include <spa/support/log.h>
  #include <spa/utils/list.h>
  #include <spa/utils/string.h>
  #include <spa/node/node.h>
  #include <spa/node/utils.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;
  #define BUFFER_FLAG_OUT	(1<<0)
  	uint32_t flags;
  	struct spa_buffer *outbuf;
  	struct spa_meta_header *h;
  	void *ptr;
  	size_t size;
  	struct spa_list link;
  };
  
  struct port {
  	enum spa_direction direction;
  	uint32_t id;
  
  	bool have_format;
  
  	uint64_t info_all;
  	struct spa_port_info info;
  	struct spa_param_info params[5];
  
  	struct buffer buffers[MAX_BUFFERS];
  	uint32_t n_buffers;
  
  	struct spa_io_buffers *io;
  
  	struct spa_list empty;
  };
  
  struct impl {
  	struct spa_handle handle;
  	struct spa_node node;
  
  	struct spa_log *log;
  	uint32_t quantum_limit;
  
  	uint64_t info_all;
  	struct spa_node_info info;
  	struct spa_param_info params[5];
  	struct props props;
  
  	struct spa_hook_list hooks;
  
  	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(void *object, int seq,
  				 uint32_t id, uint32_t start, uint32_t num,
  				 const struct spa_pod *filter)
  {
  	struct impl *this = object;
  	struct spa_pod_builder b = { 0 };
  	uint8_t buffer[1024];
  	struct spa_pod *param;
  	struct props *p;
  	struct spa_result_node_params result;
  	uint32_t count = 0;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  	spa_return_val_if_fail(num != 0, -EINVAL);
  
  	p = &this->props;
  
  	result.id = id;
  	result.next = start;
        next:
  	result.index = result.next++;
  
  	spa_pod_builder_init(&b, buffer, sizeof(buffer));
  
  	switch (id) {
  	case SPA_PARAM_PropInfo:
  		switch (result.index) {
  		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.index) {
  		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;
  	}
  
  	if (spa_pod_filter(&b, &result.param, param, filter) < 0)
  		goto next;
  
  	spa_node_emit_result(&this->hooks, seq, 0, SPA_RESULT_TYPE_NODE_PARAMS, &result);
  
  	if (++count != num)
  		goto next;
  
  	return 0;
  }
  
  static int impl_node_set_io(void *object, uint32_t id, void *data, size_t size)
  {
  	return -ENOTSUP;
  }
  
  static int impl_node_set_param(void *object, uint32_t id, uint32_t flags,
  			       const struct spa_pod *param)
  {
  	struct impl *this = object;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  
  	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(void *object, const struct spa_command *command)
  {
  	struct impl *this = object;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  	spa_return_val_if_fail(command != NULL, -EINVAL);
  
  	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_node_info(struct impl *this, bool full)
  {
  	uint64_t old = full ? this->info.change_mask : 0;
  	if (full)
  		this->info.change_mask = this->info_all;
  	if (this->info.change_mask) {
  		spa_node_emit_info(&this->hooks, &this->info);
  		this->info.change_mask = old;
  	}
  }
  
  static void emit_port_info(struct impl *this, struct port *port, bool full)
  {
  	uint64_t old = full ? port->info.change_mask : 0;
  	if (full)
  		port->info.change_mask = port->info_all;
  	if (port->info.change_mask) {
  		spa_node_emit_port_info(&this->hooks,
  				port->direction, port->id, &port->info);
  		port->info.change_mask = old;
  	}
  }
  
  static int
  impl_node_add_listener(void *object,
  		struct spa_hook *listener,
  		const struct spa_node_events *events,
  		void *data)
  {
  	struct impl *this = object;
  	struct spa_hook_list save;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  
  	spa_hook_list_isolate(&this->hooks, &save, listener, events, data);
  
  	emit_node_info(this, true);
  	emit_port_info(this, GET_IN_PORT(this, 0), true);
  	emit_port_info(this, GET_OUT_PORT(this, 0), true);
  
  	spa_hook_list_join(&this->hooks, &save);
  
  	return 0;
  }
  
  static int
  impl_node_set_callbacks(void *object,
  			const struct spa_node_callbacks *callbacks,
  			void *data)
  {
  	return 0;
  }
  
  static int impl_node_add_port(void *object, enum spa_direction direction, uint32_t port_id,
  		const struct spa_dict *props)
  {
  	return -ENOTSUP;
  }
  
  static int
  impl_node_remove_port(void *object, enum spa_direction direction, uint32_t port_id)
  {
  	return -ENOTSUP;
  }
  
  static int port_enum_formats(void *object,
  			     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(void *object, int seq,
  			enum spa_direction direction, uint32_t port_id,
  			uint32_t id, uint32_t start, uint32_t num,
  			const struct spa_pod *filter)
  {
  	struct impl *this = object;
  	struct port *port;
  	struct spa_pod_builder b = { 0 };
  	uint8_t buffer[1024];
  	struct spa_pod *param;
  	struct spa_result_node_params result;
  	uint32_t count = 0;
  	int res;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  	spa_return_val_if_fail(num != 0, -EINVAL);
  	spa_return_val_if_fail(CHECK_PORT(this, direction, port_id), -EINVAL);
  
  	port = GET_PORT(this, direction, port_id);
  
  	result.id = id;
  	result.next = start;
        next:
  	result.index = result.next++;
  
  	spa_pod_builder_init(&b, buffer, sizeof(buffer));
  
  	switch (id) {
  	case SPA_PARAM_EnumFormat:
  		if ((res = port_enum_formats(this, direction, port_id,
  						result.index, filter, &param, &b)) <= 0)
  			return res;
  		break;
  
  	case SPA_PARAM_Format:
  		if (!port->have_format)
  			return -EIO;
  		if (result.index > 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.index > 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(
  							this->quantum_limit * this->bpf,
  							16 * this->bpf,
  							INT32_MAX),
  			SPA_PARAM_BUFFERS_stride,  SPA_POD_Int(this->bpf));
  		break;
  	case SPA_PARAM_Meta:
  		switch (result.index) {
  		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.index) {
  		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;
  		default:
  			return 0;
  		}
  		break;
  	default:
  		return -ENOENT;
  	}
  
  	if (spa_pod_filter(&b, &result.param, param, filter) < 0)
  		goto next;
  
  	spa_node_emit_result(&this->hooks, seq, 0, SPA_RESULT_TYPE_NODE_PARAMS, &result);
  
  	if (++count != num)
  		goto next;
  
  	return 0;
  }
  
  static int clear_buffers(struct impl *this, struct port *port)
  {
  	if (port->n_buffers > 0) {
  		spa_log_debug(this->log, NAME " %p: clear buffers", this);
  		port->n_buffers = 0;
  		spa_list_init(&port->empty);
  	}
  	return 0;
  }
  
  static int port_set_format(void *object,
  			   enum spa_direction direction, uint32_t port_id,
  			   uint32_t flags,
  			   const struct spa_pod *format)
  {
  	struct impl *this = object;
  	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;
  	}
  
  	port->info.change_mask |= SPA_PORT_CHANGE_MASK_PARAMS;
  	if (port->have_format) {
  		port->params[3] = SPA_PARAM_INFO(SPA_PARAM_Format, SPA_PARAM_INFO_READWRITE);
  		port->params[4] = SPA_PARAM_INFO(SPA_PARAM_Buffers, SPA_PARAM_INFO_READ);
  	} else {
  		port->params[3] = SPA_PARAM_INFO(SPA_PARAM_Format, SPA_PARAM_INFO_WRITE);
  		port->params[4] = SPA_PARAM_INFO(SPA_PARAM_Buffers, 0);
  	}
  	emit_port_info(this, port, false);
  
  	return 0;
  }
  
  static int
  impl_node_port_set_param(void *object,
  			 enum spa_direction direction, uint32_t port_id,
  			 uint32_t id, uint32_t flags,
  			 const struct spa_pod *param)
  {
  	spa_return_val_if_fail(object != NULL, -EINVAL);
  
  	spa_return_val_if_fail(CHECK_PORT(object, direction, port_id), -EINVAL);
  
  	if (id == SPA_PARAM_Format) {
  		return port_set_format(object, direction, port_id, flags, param);
  	}
  	else
  		return -ENOENT;
  }
  
  static int
  impl_node_port_use_buffers(void *object,
  			   enum spa_direction direction,
  			   uint32_t port_id,
  			   uint32_t flags,
  			   struct spa_buffer **buffers,
  			   uint32_t n_buffers)
  {
  	struct impl *this = object;
  	struct port *port;
  	uint32_t i;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  	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->flags = direction == SPA_DIRECTION_INPUT ? BUFFER_FLAG_OUT : 0;
  		b->h = spa_buffer_find_meta_data(buffers[i], SPA_META_Header, sizeof(*b->h));
  
  		if (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 (!SPA_FLAG_IS_SET(b->flags, BUFFER_FLAG_OUT))
  			spa_list_append(&port->empty, &b->link);
  	}
  	port->n_buffers = n_buffers;
  
  	return 0;
  }
  
  static int
  impl_node_port_set_io(void *object,
  		      enum spa_direction direction,
  		      uint32_t port_id,
  		      uint32_t id,
  		      void *data, size_t size)
  {
  	struct impl *this = object;
  	struct port *port;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  	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;
  	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 (!SPA_FLAG_IS_SET(b->flags, BUFFER_FLAG_OUT)) {
  		spa_log_warn(this->log, NAME " %p: buffer %d not outstanding", this, id);
  		return;
  	}
  
  	spa_list_append(&port->empty, &b->link);
  	SPA_FLAG_CLEAR(b->flags, BUFFER_FLAG_OUT);
  	spa_log_trace(this->log, NAME " %p: recycle buffer %d", this, id);
  }
  
  static int impl_node_port_reuse_buffer(void *object, uint32_t port_id, uint32_t buffer_id)
  {
  	struct impl *this = object;
  	struct port *port;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  	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);
  	SPA_FLAG_SET(b->flags, BUFFER_FLAG_OUT);
  
  	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_PTROFF(sd[0].data, soffset, int16_t);
  		dst = SPA_PTROFF(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(void *object)
  {
  	struct impl *this = object;
  	struct port *in_port, *out_port;
  	struct spa_io_buffers *input, *output;
  	struct buffer *dbuf, *sbuf;
  
  	spa_return_val_if_fail(this != NULL, -EINVAL);
  
  	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_DATA)
  		return SPA_STATUS_HAVE_DATA;
  
  	/* 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_DATA)
  		return SPA_STATUS_NEED_DATA;
  
  	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_DATA;
  
  	input->status = SPA_STATUS_NEED_DATA;
  
  	return SPA_STATUS_HAVE_DATA;
  }
  
  static const struct spa_node_methods impl_node = {
  	SPA_VERSION_NODE_METHODS,
  	.add_listener = impl_node_add_listener,
  	.set_callbacks = impl_node_set_callbacks,
  	.enum_params = impl_node_enum_params,
  	.set_param = impl_node_set_param,
  	.set_io = impl_node_set_io,
  	.send_command = impl_node_send_command,
  	.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_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, const char *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 (spa_streq(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;
  
  	this->log = spa_support_find(support, n_support, SPA_TYPE_INTERFACE_Log);
  
  	for (i = 0; info && i < info->n_items; i++) {
  		const char *k = info->items[i].key;
  		const char *s = info->items[i].value;
  		if (spa_streq(k, "clock.quantum-limit"))
  			spa_atou32(s, &this->quantum_limit, 0);
  	}
  
  	spa_hook_list_init(&this->hooks);
  
  	this->node.iface = SPA_INTERFACE_INIT(
  			SPA_TYPE_INTERFACE_Node,
  			SPA_VERSION_NODE,
  			&impl_node, this);
  	this->info_all = SPA_NODE_CHANGE_MASK_FLAGS |
  			SPA_NODE_CHANGE_MASK_PARAMS;
  	this->info = SPA_NODE_INFO_INIT();
  	this->info.max_input_ports = 1;
  	this->info.max_output_ports = 1;
  	this->info.flags = SPA_NODE_FLAG_RT;
  	this->params[0] = SPA_PARAM_INFO(SPA_PARAM_PropInfo, SPA_PARAM_INFO_READ);
  	this->params[1] = SPA_PARAM_INFO(SPA_PARAM_Props, SPA_PARAM_INFO_READWRITE);
  	this->info.params = this->params;
  	this->info.n_params = 2;
  	reset_props(&this->props);
  
  	port = GET_IN_PORT(this, 0);
  	port->direction = SPA_DIRECTION_INPUT;
  	port->id = 0;
  	port->info_all = SPA_PORT_CHANGE_MASK_FLAGS |
  			SPA_PORT_CHANGE_MASK_PARAMS;
  	port->info = SPA_PORT_INFO_INIT();
  	port->info.flags = SPA_PORT_FLAG_IN_PLACE;
  	port->params[0] = SPA_PARAM_INFO(SPA_PARAM_EnumFormat, SPA_PARAM_INFO_READ);
  	port->params[1] = SPA_PARAM_INFO(SPA_PARAM_Meta, SPA_PARAM_INFO_READ);
  	port->params[2] = SPA_PARAM_INFO(SPA_PARAM_IO, SPA_PARAM_INFO_READ);
  	port->params[3] = SPA_PARAM_INFO(SPA_PARAM_Format, SPA_PARAM_INFO_WRITE);
  	port->params[4] = SPA_PARAM_INFO(SPA_PARAM_Buffers, 0);
  	port->info.params = port->params;
  	port->info.n_params = 5;
  	spa_list_init(&port->empty);
  
  	port = GET_OUT_PORT(this, 0);
  	port->direction = SPA_DIRECTION_OUTPUT;
  	port->id = 0;
  	port->info_all = SPA_PORT_CHANGE_MASK_FLAGS |
  			SPA_PORT_CHANGE_MASK_PARAMS;
  	port->info = SPA_PORT_INFO_INIT();
  	port->info.flags = SPA_PORT_FLAG_NO_REF;
  	port->params[0] = SPA_PARAM_INFO(SPA_PARAM_EnumFormat, SPA_PARAM_INFO_READ);
  	port->params[1] = SPA_PARAM_INFO(SPA_PARAM_Meta, SPA_PARAM_INFO_READ);
  	port->params[2] = SPA_PARAM_INFO(SPA_PARAM_IO, SPA_PARAM_INFO_READ);
  	port->params[3] = SPA_PARAM_INFO(SPA_PARAM_Format, SPA_PARAM_INFO_WRITE);
  	port->params[4] = SPA_PARAM_INFO(SPA_PARAM_Buffers, 0);
  	port->info.params = port->params;
  	port->info.n_params = 5;
  	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,
  };
  