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/* lv2_event.h - C header file for the LV2 events extension.
*
* Copyright (C) 2006-2007 Lars Luthman <lars.luthman@gmail.com>
* Copyright (C) 2008-2009 David Robillard <http://drobilla.net>
*
* This header 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 of the License, or
* (at your option) any later version.
*
* This header 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 header; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 01222-1307 USA
*/
#ifndef LV2_EVENT_H
#define LV2_EVENT_H
#define LV2_EVENT_URI "http://lv2plug.in/ns/ext/event"
#define LV2_EVENT_AUDIO_STAMP 0
#include <stdint.h>
/** @file
* C header for the LV2 Event extension <http://lv2plug.in/ns/ext/event>.
*
* This extension is a generic transport mechanism for time stamped events
* of any type (e.g. MIDI, OSC, ramps, etc). Each port can transport mixed
* events of any type; the type of events and timestamps are defined by a URI
* which is mapped to an integer by the host for performance reasons.
*
* This extension requires the host to support the LV2 URI Map extension.
* Any host which supports this extension MUST guarantee that any call to
* the LV2 URI Map uri_to_id function with the URI of this extension as the
* 'map' argument returns a value within the range of uint16_t.
*/
/** The best Pulses Per Quarter Note for tempo-based uint32_t timestmaps.
* Equal to 2^12 * 5 * 7 * 9 * 11 * 13 * 17, which is evenly divisble
* by all integers from 1 through 18 inclusive, and powers of 2 up to 2^12.
*/
static const uint32_t LV2_EVENT_PPQN = 3136573440U;
/** An LV2 event (header only).
*
* LV2 events are generic time-stamped containers for any type of event.
* The type field defines the format of a given event's contents.
*
* This struct defines the header of an LV2 event. An LV2 event is a single
* chunk of POD (plain old data), usually contained in a flat buffer
* (see LV2_EventBuffer below). Unless a required feature says otherwise,
* hosts may assume a deep copy of an LV2 event can be created safely
* using a simple:
*
* memcpy(ev_copy, ev, sizeof(LV2_Event) + ev->size); (or equivalent)
*/
typedef struct {
/** The frames portion of timestamp. The units used here can optionally be
* set for a port (with the lv2ev:timeUnits property), otherwise this
* is audio frames, corresponding to the sample_count parameter of the
* LV2 run method (e.g. frame 0 is the first frame for that call to run).
*/
uint32_t frames;
/** The sub-frames portion of timestamp. The units used here can
* optionally be set for a port (with the lv2ev:timeUnits property),
* otherwise this is 1/(2^32) of an audio frame.
*/
uint32_t subframes;
/** The type of this event, as a number which represents some URI
* defining an event type. This value MUST be some value previously
* returned from a call to the uri_to_id function defined in the LV2
* URI map extension (see lv2_uri_map.h).
* There are special rules which must be followed depending on the type
* of an event. If the plugin recognizes an event type, the definition
* of that event type will describe how to interpret the event, and
* any required behaviour. Otherwise, if the type is 0, this event is a
* non-POD event and lv2_event_unref MUST be called if the event is
* 'dropped' (see above). Even if the plugin does not understand an event,
* it may pass the event through to an output by simply copying (and NOT
* calling lv2_event_unref). These rules are designed to allow for generic
* event handling plugins and large non-POD events, but with minimal hassle
* on simple plugins that "don't care" about these more advanced features.
*/
uint16_t type;
/** The size of the data portion of this event in bytes, which immediately
* follows. The header size (12 bytes) is not included in this value.
*/
uint16_t size;
/* size bytes of data follow here */
} LV2_Event;
/** A buffer of LV2 events (header only).
*
* Like events (which this contains) an event buffer is a single chunk of POD:
* the entire buffer (including contents) can be copied with a single memcpy.
* The first contained event begins sizeof(LV2_EventBuffer) bytes after
* the start of this struct.
*
* After this header, the buffer contains an event header (defined by struct
* LV2_Event), followed by that event's contents (padded to 64 bits), followed by
* another header, etc:
*
* | | | | | | |
* | | | | | | | | | | | | | | | | | | | | | | | | |
* |FRAMES |SUBFRMS|TYP|LEN|DATA..DATA..PAD|FRAMES | ...
*/
typedef struct {
/** The contents of the event buffer. This may or may not reside in the
* same block of memory as this header, plugins must not assume either.
* The host guarantees this points to at least capacity bytes of allocated
* memory (though only size bytes of that are valid events).
*/
uint8_t* data;
/** The size of this event header in bytes (including everything).
*
* This is to allow for extending this header in the future without
* breaking binary compatibility. Whenever this header is copied,
* it MUST be done using this field (and NOT the sizeof this struct).
*/
uint16_t header_size;
/** The type of the time stamps for events in this buffer.
* As a special exception, '0' always means audio frames and subframes
* (1/UINT32_MAX'th of a frame) in the sample rate passed to instantiate.
* INPUTS: The host must set this field to the numeric ID of some URI
* defining the meaning of the frames/subframes fields of contained
* events (obtained by the LV2 URI Map uri_to_id function with the URI
* of this extension as the 'map' argument, see lv2_uri_map.h).
* The host must never pass a plugin a buffer which uses a stamp type
* the plugin does not 'understand'. The value of this field must
* never change, except when connect_port is called on the input
* port, at which time the host MUST have set the stamp_type field to
* the value that will be used for all subsequent run calls.
* OUTPUTS: The plugin may set this to any value that has been returned
* from uri_to_id with the URI of this extension for a 'map' argument.
* When connected to a buffer with connect_port, output ports MUST set
* this field to the type of time stamp they will be writing. On any
* call to connect_port on an event input port, the plugin may change
* this field on any output port, it is the responsibility of the host
* to check if any of these values have changed and act accordingly.
*/
uint16_t stamp_type;
/** The number of events in this buffer.
* INPUTS: The host must set this field to the number of events
* contained in the data buffer before calling run().
* The plugin must not change this field.
* OUTPUTS: The plugin must set this field to the number of events it
* has written to the buffer before returning from run().
* Any initial value should be ignored by the plugin.
*/
uint32_t event_count;
/** The size of the data buffer in bytes.
* This is set by the host and must not be changed by the plugin.
* The host is allowed to change this between run() calls.
*/
uint32_t capacity;
/** The size of the initial portion of the data buffer containing data.
* INPUTS: The host must set this field to the number of bytes used
* by all events it has written to the buffer (including headers)
* before calling the plugin's run().
* The plugin must not change this field.
* OUTPUTS: The plugin must set this field to the number of bytes
* used by all events it has written to the buffer (including headers)
* before returning from run().
* Any initial value should be ignored by the plugin.
*/
uint32_t size;
} LV2_Event_Buffer;
/** Opaque pointer to host data. */
typedef void* LV2_Event_Callback_Data;
/** The data field of the LV2_Feature for this extension.
*
* To support this feature the host must pass an LV2_Feature struct to the
* plugin's instantiate method with URI "http://lv2plug.in/ns/ext/event"
* and data pointed to an instance of this struct.
*/
typedef struct {
/** Opaque pointer to host data.
*
* The plugin MUST pass this to any call to functions in this struct.
* Otherwise, it must not be interpreted in any way.
*/
LV2_Event_Callback_Data callback_data;
/** Take a reference to a non-POD event.
*
* If a plugin receives an event with type 0, it means the event is a
* pointer to some object in memory and not a flat sequence of bytes
* in the buffer. When receiving a non-POD event, the plugin already
* has an implicit reference to the event. If the event is stored AND
* passed to an output, lv2_event_ref MUST be called on that event.
* If the event is only stored OR passed through, this is not necessary
* (as the plugin already has 1 implicit reference).
*
* @param event An event received at an input that will not be copied to
* an output or stored in any way.
* @param context The calling context. (Like event types) this is a mapped
* URI, see lv2_context.h. Simple plugin with just a run()
* method should pass 0 here (the ID of the 'standard' LV2
* run context). The host guarantees that this function is
* realtime safe iff @a context is realtime safe.
*
* PLUGINS THAT VIOLATE THESE RULES MAY CAUSE CRASHES AND MEMORY LEAKS.
*/
uint32_t (*lv2_event_ref)(LV2_Event_Callback_Data callback_data,
LV2_Event* event);
/** Drop a reference to a non-POD event.
*
* If a plugin receives an event with type 0, it means the event is a
* pointer to some object in memory and not a flat sequence of bytes
* in the buffer. If the plugin does not pass the event through to
* an output or store it internally somehow, it MUST call this function
* on the event (more information on using non-POD events below).
*
* @param event An event received at an input that will not be copied to
* an output or stored in any way.
* @param context The calling context. (Like event types) this is a mapped
* URI, see lv2_context.h. Simple plugin with just a run()
* method should pass 0 here (the ID of the 'standard' LV2
* run context). The host guarantees that this function is
* realtime safe iff @a context is realtime safe.
*
* PLUGINS THAT VIOLATE THESE RULES MAY CAUSE CRASHES AND MEMORY LEAKS.
*/
uint32_t (*lv2_event_unref)(LV2_Event_Callback_Data callback_data,
LV2_Event* event);
} LV2_Event_Feature;
#endif /* LV2_EVENT_H */
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