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-rw-r--r--plugins/eg02-midigate.lv2/midigate.c223
1 files changed, 223 insertions, 0 deletions
diff --git a/plugins/eg02-midigate.lv2/midigate.c b/plugins/eg02-midigate.lv2/midigate.c
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+++ b/plugins/eg02-midigate.lv2/midigate.c
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+/*
+ 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;
+ }
+}