juce/source/src/audio/plugin_client/LV2/includes/lv2_event.h

   1 /*
   2   LV2 Event Extension
   3   Copyright 2008-2011 David Robillard <http://drobilla.net>
   4   Copyright 2006-2007 Lars Luthman <lars.luthman@gmail.com>
   5
   6   Permission to use, copy, modify, and/or distribute this software for any
   7   purpose with or without fee is hereby granted, provided that the above
   8   copyright notice and this permission notice appear in all copies.
   9
  10   THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13   ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17 */
  18
  19 #ifndef LV2_EVENT_H
  20 #define LV2_EVENT_H
  21
  22 #define LV2_EVENT_URI "http://lv2plug.in/ns/ext/event"
  23 #define LV2_EVENT_AUDIO_STAMP 0
  24
  25 #include <stdint.h>
  26
  27 /**
  28    @file event.h
  29    C API for the LV2 Event extension <http://lv2plug.in/ns/ext/event>.
  30
  31    This extension is a generic transport mechanism for time stamped events
  32    of any type (e.g. MIDI, OSC, ramps, etc). Each port can transport mixed
  33    events of any type; the type of events and timestamps are defined by a URI
  34    which is mapped to an integer by the host for performance reasons.
  35
  36    This extension requires the host to support the LV2 URI Map extension.
  37    Any host which supports this extension MUST guarantee that any call to
  38    the LV2 URI Map uri_to_id function with the URI of this extension as the
  39    'map' argument returns a value within the range of uint16_t.
  40 */
  41
  42 /**
  43    The best Pulses Per Quarter Note for tempo-based uint32_t timestamps.
  44    Equal to 2^12 * 5 * 7 * 9 * 11 * 13 * 17, which is evenly divisble
  45    by all integers from 1 through 18 inclusive, and powers of 2 up to 2^12.
  46 */
  47 static const uint32_t LV2_EVENT_PPQN = 3136573440U;
  48
  49 /**
  50    An LV2 event (header only).
  51
  52    LV2 events are generic time-stamped containers for any type of event.
  53    The type field defines the format of a given event's contents.
  54
  55    This struct defines the header of an LV2 event. An LV2 event is a single
  56    chunk of POD (plain old data), usually contained in a flat buffer (see
  57    LV2_EventBuffer below). Unless a required feature says otherwise, hosts may
  58    assume a deep copy of an LV2 event can be created safely using a simple:
  59
  60    memcpy(ev_copy, ev, sizeof(LV2_Event) + ev->size);  (or equivalent)
  61 */
  62 typedef struct {
  63
  64         /**
  65            The frames portion of timestamp. The units used here can optionally be
  66            set for a port (with the lv2ev:timeUnits property), otherwise this is
  67            audio frames, corresponding to the sample_count parameter of the LV2 run
  68            method (e.g. frame 0 is the first frame for that call to run).
  69         */
  70         uint32_t frames;
  71
  72         /**
  73            The sub-frames portion of timestamp. The units used here can optionally
  74            be set for a port (with the lv2ev:timeUnits property), otherwise this is
  75            1/(2^32) of an audio frame.
  76         */
  77         uint32_t subframes;
  78
  79         /**
  80            The type of this event, as a number which represents some URI
  81            defining an event type. This value MUST be some value previously
  82            returned from a call to the uri_to_id function defined in the LV2
  83            URI map extension (see lv2_uri_map.h).
  84            There are special rules which must be followed depending on the type
  85            of an event. If the plugin recognizes an event type, the definition
  86            of that event type will describe how to interpret the event, and
  87            any required behaviour. Otherwise, if the type is 0, this event is a
  88            non-POD event and lv2_event_unref MUST be called if the event is
  89            'dropped' (see above). Even if the plugin does not understand an event,
  90            it may pass the event through to an output by simply copying (and NOT
  91            calling lv2_event_unref). These rules are designed to allow for generic
  92            event handling plugins and large non-POD events, but with minimal hassle
  93            on simple plugins that "don't care" about these more advanced features.
  94         */
  95         uint16_t type;
  96
  97         /**
  98            The size of the data portion of this event in bytes, which immediately
  99            follows. The header size (12 bytes) is not included in this value.
 100         */
 101         uint16_t size;
 102
 103         /* size bytes of data follow here */
 104
 105 } LV2_Event;
 106
 107
 108 /**
 109    A buffer of LV2 events (header only).
 110
 111    Like events (which this contains) an event buffer is a single chunk of POD:
 112    the entire buffer (including contents) can be copied with a single memcpy.
 113    The first contained event begins sizeof(LV2_EventBuffer) bytes after the
 114    start of this struct.
 115
 116    After this header, the buffer contains an event header (defined by struct
 117    LV2_Event), followed by that event's contents (padded to 64 bits), followed
 118    by another header, etc:
 119
 120    |       |       |       |       |       |       |
 121    | | | | | | | | | | | | | | | | | | | | | | | | |
 122    |FRAMES |SUBFRMS|TYP|LEN|DATA..DATA..PAD|FRAMES | ...
 123 */
 124 typedef struct {
 125
 126         /**
 127            The contents of the event buffer. This may or may not reside in the
 128            same block of memory as this header, plugins must not assume either.
 129            The host guarantees this points to at least capacity bytes of allocated
 130            memory (though only size bytes of that are valid events).
 131         */
 132         uint8_t* data;
 133
 134         /**
 135            The size of this event header in bytes (including everything).
 136
 137            This is to allow for extending this header in the future without
 138            breaking binary compatibility. Whenever this header is copied,
 139            it MUST be done using this field (and NOT the sizeof this struct).
 140         */
 141         uint16_t header_size;
 142
 143         /**
 144            The type of the time stamps for events in this buffer.
 145            As a special exception, '0' always means audio frames and subframes
 146            (1/UINT32_MAX'th of a frame) in the sample rate passed to instantiate.
 147
 148            INPUTS: The host must set this field to the numeric ID of some URI
 149            defining the meaning of the frames/subframes fields of contained events
 150            (obtained by the LV2 URI Map uri_to_id function with the URI of this
 151            extension as the 'map' argument, see lv2_uri_map.h).  The host must
 152            never pass a plugin a buffer which uses a stamp type the plugin does not
 153            'understand'. The value of this field must never change, except when
 154            connect_port is called on the input port, at which time the host MUST
 155            have set the stamp_type field to the value that will be used for all
 156            subsequent run calls.
 157
 158            OUTPUTS: The plugin may set this to any value that has been returned
 159            from uri_to_id with the URI of this extension for a 'map' argument.
 160            When connected to a buffer with connect_port, output ports MUST set this
 161            field to the type of time stamp they will be writing. On any call to
 162            connect_port on an event input port, the plugin may change this field on
 163            any output port, it is the responsibility of the host to check if any of
 164            these values have changed and act accordingly.
 165         */
 166         uint16_t stamp_type;
 167
 168         /**
 169            The number of events in this buffer.
 170
 171            INPUTS: The host must set this field to the number of events contained
 172            in the data buffer before calling run(). The plugin must not change
 173            this field.
 174
 175            OUTPUTS: The plugin must set this field to the number of events it has
 176            written to the buffer before returning from run(). Any initial value
 177            should be ignored by the plugin.
 178         */
 179         uint32_t event_count;
 180
 181         /**
 182            The size of the data buffer in bytes.
 183            This is set by the host and must not be changed by the plugin.
 184            The host is allowed to change this between run() calls.
 185         */
 186         uint32_t capacity;
 187
 188         /**
 189            The size of the initial portion of the data buffer containing data.
 190
 191            INPUTS: The host must set this field to the number of bytes used
 192            by all events it has written to the buffer (including headers)
 193            before calling the plugin's run().
 194            The plugin must not change this field.
 195
 196            OUTPUTS: The plugin must set this field to the number of bytes
 197            used by all events it has written to the buffer (including headers)
 198            before returning from run().
 199            Any initial value should be ignored by the plugin.
 200         */
 201         uint32_t size;
 202
 203 } LV2_Event_Buffer;
 204
 205
 206 /**
 207    Opaque pointer to host data.
 208 */
 209 typedef void* LV2_Event_Callback_Data;
 210
 211
 212 /**
 213    Non-POD events feature.
 214
 215    To support this feature the host must pass an LV2_Feature struct to the
 216    plugin's instantiate method with URI "http://lv2plug.in/ns/ext/event"
 217    and data pointed to an instance of this struct.  Note this feature
 218    is not mandatory to support the event extension.
 219 */
 220 typedef struct {
 221
 222         /**
 223            Opaque pointer to host data.
 224
 225            The plugin MUST pass this to any call to functions in this struct.
 226            Otherwise, it must not be interpreted in any way.
 227         */
 228         LV2_Event_Callback_Data callback_data;
 229
 230         /**
 231            Take a reference to a non-POD event.
 232
 233            If a plugin receives an event with type 0, it means the event is a
 234            pointer to some object in memory and not a flat sequence of bytes
 235            in the buffer. When receiving a non-POD event, the plugin already
 236            has an implicit reference to the event. If the event is stored AND
 237            passed to an output, lv2_event_ref MUST be called on that event.
 238            If the event is only stored OR passed through, this is not necessary
 239            (as the plugin already has 1 implicit reference).
 240
 241            @param event An event received at an input that will not be copied to
 242            an output or stored in any way.
 243
 244            @param context The calling context. Like event types, this is a mapped
 245            URI, see lv2_context.h. Simple plugin with just a run() method should
 246            pass 0 here (the ID of the 'standard' LV2 run context). The host
 247            guarantees that this function is realtime safe iff @a context is
 248            realtime safe.
 249
 250            PLUGINS THAT VIOLATE THESE RULES MAY CAUSE CRASHES AND MEMORY LEAKS.
 251         */
 252         uint32_t (*lv2_event_ref)(LV2_Event_Callback_Data callback_data,
 253                                   LV2_Event*              event);
 254
 255         /**
 256            Drop a reference to a non-POD event.
 257
 258            If a plugin receives an event with type 0, it means the event is a
 259            pointer to some object in memory and not a flat sequence of bytes
 260            in the buffer. If the plugin does not pass the event through to
 261            an output or store it internally somehow, it MUST call this function
 262            on the event (more information on using non-POD events below).
 263
 264            @param event An event received at an input that will not be copied to an
 265            output or stored in any way.
 266
 267            @param context The calling context. Like event types, this is a mapped
 268            URI, see lv2_context.h. Simple plugin with just a run() method should
 269            pass 0 here (the ID of the 'standard' LV2 run context). The host
 270            guarantees that this function is realtime safe iff @a context is
 271            realtime safe.
 272
 273            PLUGINS THAT VIOLATE THESE RULES MAY CAUSE CRASHES AND MEMORY LEAKS.
 274         */
 275         uint32_t (*lv2_event_unref)(LV2_Event_Callback_Data callback_data,
 276                                     LV2_Event*              event);
 277
 278 } LV2_Event_Feature;
 279
 280
 281 #endif /* LV2_EVENT_H */