Order examples in a sensible progression for the book.

1 files changed, 223 insertions, 0 deletions

diff --git a/plugins/eg02-midigate.lv2/midigate.c b/plugins/eg02-midigate.lv2/midigate.c
new file mode 100644
index 0000000..3b74bfc
--- /dev/null
+++ b/plugins/eg02-midigate.lv2/midigate.c
@@ -0,0 +1,223 @@
+/*
+  Copyright 2013 David Robillard <d@drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include <stdio.h>
+
+#include <math.h>
+#include <stdlib.h>
+
+#include "lv2/lv2plug.in/ns/ext/atom/atom.h"
+#include "lv2/lv2plug.in/ns/ext/atom/util.h"
+#include "lv2/lv2plug.in/ns/ext/midi/midi.h"
+#include "lv2/lv2plug.in/ns/ext/urid/urid.h"
+#include "lv2/lv2plug.in/ns/lv2core/lv2.h"
+
+#define MIDIGATE_URI "http://lv2plug.in/plugins/eg-midigate"
+
+typedef enum {
+	MIDIGATE_CONTROL = 0,
+	MIDIGATE_IN      = 1,
+	MIDIGATE_OUT     = 2
+} PortIndex;
+
+typedef struct {
+	// Port buffers
+	const LV2_Atom_Sequence* control;
+	const float*             in;
+	float*                   out;
+
+	// Features
+	LV2_URID_Map* map;
+
+	struct {
+		LV2_URID midi_MidiEvent;
+	} uris;
+
+	unsigned n_active_notes;
+	unsigned program;
+} Midigate;
+
+static LV2_Handle
+instantiate(const LV2_Descriptor*     descriptor,
+            double                    rate,
+            const char*               bundle_path,
+            const LV2_Feature* const* features)
+{
+	/** Scan features array for the URID feature we need. */
+	LV2_URID_Map* map = NULL;
+	for (int i = 0; features[i]; ++i) {
+		if (!strcmp(features[i]->URI, LV2_URID__map)) {
+			map = (LV2_URID_Map*)features[i]->data;
+			break;
+		}
+	}
+	if (!map) {
+		/**
+		   No URID feature given.  This is a host bug since we require this
+		   feature, but should be handled gracefully anyway.
+		*/
+		return NULL;
+	}
+
+	Midigate* self = (Midigate*)calloc(1, sizeof(Midigate));
+	self->map = map;
+	self->uris.midi_MidiEvent = map->map(map->handle, LV2_MIDI__MidiEvent);
+
+	return (LV2_Handle)self;
+}
+
+static void
+connect_port(LV2_Handle instance,
+             uint32_t   port,
+             void*      data)
+{
+	Midigate* self = (Midigate*)instance;
+
+	switch ((PortIndex)port) {
+	case MIDIGATE_CONTROL:
+		self->control = (const LV2_Atom_Sequence*)data;
+		break;
+	case MIDIGATE_IN:
+		self->in = (const float*)data;
+		break;
+	case MIDIGATE_OUT:
+		self->out = (float*)data;
+		break;
+	}
+}
+
+static void
+activate(LV2_Handle instance)
+{
+	Midigate* self = (Midigate*)instance;
+	self->n_active_notes = 0;
+	self->program        = 0;
+}
+
+/**
+   A function to write a chunk of output, to be called from run().  If the gate
+   is high, then the input will be passed through for this chunk, otherwise
+   silence is written.
+*/
+static void
+write_output(Midigate* self, uint32_t offset, uint32_t len)
+{
+	const bool active = (self->program == 0)
+		? (self->n_active_notes > 0)
+		: (self->n_active_notes == 0);
+	if (active) {
+		memcpy(self->out + offset, self->in + offset, len * sizeof(float));
+	} else {
+		memset(self->out + offset, 0, len * sizeof(float));
+	}
+}
+
+/**
+   This plugin works through the cycle in chunks starting at offset zero.  The
+   +offset+ represents the current time within this this cycle, so
+   the output from 0 to +offset+ has already been written.
+
+   MIDI events are read in a loop.  In each iteration, the number of active
+   notes (on note on and note off) or the program (on program change) is
+   updated, then the output is written up until the current event time.  Then
+   +offset+ is updated and the next event is processed.  After the loop the
+   final chunk from the last event to the end of the cycle is emitted.
+
+   This pattern of iterating over input events and writing output along the way
+   is a common idiom for writing sample accurate output based on event input.
+
+   Note that this simple example simply writes input or zero for each sample
+   based on the gate.  A serious implementation would need to envelope the
+   transition to avoid aliasing.
+*/
+static void
+run(LV2_Handle instance, uint32_t sample_count)
+{
+	Midigate* self   = (Midigate*)instance;
+	uint32_t  offset = 0;
+
+	LV2_ATOM_SEQUENCE_FOREACH(self->control, ev) {
+		if (ev->body.type == self->uris.midi_MidiEvent) {
+			const uint8_t* const msg = (const uint8_t*)(ev + 1);
+			switch (lv2_midi_message_type(msg)) {
+			case LV2_MIDI_MSG_NOTE_ON:
+				++self->n_active_notes;
+				break;
+			case LV2_MIDI_MSG_NOTE_OFF:
+				--self->n_active_notes;
+				break;
+			case LV2_MIDI_MSG_PGM_CHANGE:
+				if (msg[1] == 0 || msg[1] == 1) {
+					self->program = msg[1];
+				}
+				break;
+			default: break;
+			}
+		}
+
+		write_output(self, offset, ev->time.frames - offset);
+		offset = ev->time.frames;
+	}
+
+	write_output(self, offset, sample_count - offset);
+}
+
+/**
+   We have no resources to free on deactivation.
+   Note that the next call to activate will re-initialise the state, namely
+   self->n_active_notes, so there is no need to do so here.
+*/
+static void
+deactivate(LV2_Handle instance)
+{}
+
+static void
+cleanup(LV2_Handle instance)
+{
+	free(instance);
+}
+
+/**
+   This plugin also has no extension data to return.
+*/
+static const void*
+extension_data(const char* uri)
+{
+	return NULL;
+}
+
+static const LV2_Descriptor descriptor = {
+	MIDIGATE_URI,
+	instantiate,
+	connect_port,
+	activate,
+	run,
+	deactivate,
+	cleanup,
+	extension_data
+};
+
+LV2_SYMBOL_EXPORT
+const LV2_Descriptor*
+lv2_descriptor(uint32_t index)
+{
+	switch (index) {
+	case 0:
+		return &descriptor;
+	default:
+		return NULL;
+	}
+}