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Diffstat (limited to 'plugins/eg-midigate.lv2/midigate.c')
| -rw-r--r-- | plugins/eg-midigate.lv2/midigate.c | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/plugins/eg-midigate.lv2/midigate.c b/plugins/eg-midigate.lv2/midigate.c new file mode 100644 index 0000000..3b74bfc --- /dev/null +++ b/plugins/eg-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; + } +} |