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+/* lv2_events.h - C header file for the LV2 events extension.
+ * 
+ * Copyright (C) 2006-2007 Lars Luthman <lars.luthman@gmail.com>
+ * Copyright (C) 2008 Dave Robillard <dave@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_EVENTS_H
+#define LV2_EVENTS_H
+
+#include <stdint.h>
+
+/** @file
+ * This header defines the code portion of the LV2 events extension with URI
+ * <http://lv2plug.in/ns/ext/events> (preferred prefix 'lv2ev').
+ *
+ * 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 is defined by a URI (in some other
+ * extension) which is mapped to an integer by the host for performance
+ * reasons.
+ */
+
+
+/** The PPQN (pulses per quarter note) of tempo-based LV2 event time stamps.
+ * Equal to (2^5 * 3^4 * 5 * 7 * 11 * 13 * 17 * 19), which is evenly divisuble
+ * by all integers from 1 through 22 inclusive. */
+static const uint32_t LV2_EVENT_PPQN = 4190266080;
+
+
+
+/** Opaque host data passed to LV2_Event_Feature.
+ */
+typedef void* LV2_Event_Callback_Data;
+
+
+
+/** The data part of the LV2_Feature for the LV2 events extension.
+ *
+ * The host MUST pass an LV2_Feature struct to the plugin's instantiate
+ * method with URI set to "http://lv2plug.in/ns/ext/events" and data
+ * set to an instance of this struct.
+ *
+ * The plugin MUST pass callback_data to any invocation of the functions
+ * defined in this struct.  Otherwise, callback_data is opaque and the
+ * plugin MUST NOT interpret its value in any way.
+ */
+typedef struct {
+
+	/** Get the numeric version of an event type from the host.
+	 *
+	 * The returned value is 0 if there is no type by that URI.
+	 * The returned value correlates to the type field of LV2_Event, and is
+	 * guaranteed never to change over the course of the plugin's
+	 * instantiation, unless the returned value is 0 (i.e. new event types
+	 * can be added, but existing ones can never be changed/removed).
+	 */
+	uint16_t (*uri_to_event_type)(LV2_Event_Callback_Data callback_data,
+	                              char const*             uri);
+	
+	LV2_Event_Callback_Data callback_data;
+
+} LV2_Event_Feature;
+
+
+
+/** An LV2 event.
+ *
+ * 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 defined 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, where this numeric value refers to some URI
+	 * defining an event type.  The LV2_Event_Feature passed from the host
+	 * provides a function to map URIs to event types for this field.
+	 * The type 0 is a special nil value, meaning the event has no type and
+	 * should be ignored or passed through without interpretation.
+	 * Plugins MUST gracefully ignore or pass through any events of a type
+	 * which the plugin does not recognize.
+	 */
+	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.
+ *
+ * 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 number of events in this buffer.
+	 * INPUT PORTS: 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.
+	 * OUTPUT PORTS: 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.
+	 *  INPUT PORTS: 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.
+	 *  OUTPUT PORTS: 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;
+
+
+#endif // LV2_EVENTS_H
+