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+/*
+ Copyright 2012 Harry van Haaren <harryhaaren@gmail.com>
+ Copyright 2012 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.
+*/
+
+/**
+ @file synth.c Implementation of the LV2 Sin Synth example plugin.
+
+ This is a simple LV2 synthesis plugin that demonstrates how to receive MIDI
+ events and render audio in response to them.
+*/
+
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lv2/lv2plug.in/ns/lv2core/lv2.h"
+
+#define SYNTH_URI "http://lv2plug.in/plugins/eg-synth"
+
+/** Port indices. */
+typedef enum {
+ SYNTH_FREQ = 0,
+ SYNTH_OUTPUT,
+} PortIndex;
+
+/** Plugin instance. */
+typedef struct {
+ // Sample rate, necessary to generate sin wave in run()
+ double sample_rate;
+
+ // Current wave phase
+ float phase;
+
+ // Port buffers
+ float* freq;
+ float* input;
+ float* output;
+} Synth;
+
+/** Create a new plugin instance. */
+static LV2_Handle
+instantiate(const LV2_Descriptor* descriptor,
+ double rate,
+ const char* bundle_path,
+ const LV2_Feature* const* features)
+{
+ Synth* self = (Synth*)malloc(sizeof(Synth));
+
+ // Store the sample rate so it is available in run()
+ self->sample_rate = rate;
+
+ return (LV2_Handle)self;
+}
+
+/** Connect a port to a buffer (audio thread, must be RT safe). */
+static void
+connect_port(LV2_Handle instance,
+ uint32_t port,
+ void* data)
+{
+ Synth* self = (Synth*)instance;
+
+ switch ((PortIndex)port) {
+ case SYNTH_FREQ:
+ self->freq = (float*)data;
+ break;
+ case SYNTH_OUTPUT:
+ self->output = (float*)data;
+ break;
+ }
+}
+
+/** Initialise and prepare the plugin instance for running. */
+static void
+activate(LV2_Handle instance)
+{
+ Synth* self = (Synth*)instance;
+
+ // Initialize phase so we start at the beginning of the wave
+ self->phase = 0.0f;
+}
+
+/** Process a block of audio (audio thread, must be RT safe). */
+static void
+run(LV2_Handle instance, uint32_t n_samples)
+{
+ Synth* self = (Synth*)instance;
+
+ const float PI = 3.1415;
+ const float volume = 0.3;
+ const float freq = *(self->freq);
+ float* const output = self->output;
+
+ float samples_per_cycle = self->sample_rate / freq;
+
+ /* Calculate the phase offset per sample. Phase ranges from 0..1, so
+ phase_increment is a floating point number such that we get "freq"
+ number of cycles in "sample_rate" amount of samples. */
+ float phase_increment = (1.f / samples_per_cycle);
+
+ for (uint32_t pos = 0; pos < n_samples; pos++) {
+
+ /* Calculate the next sample. Phase ranges from 0..1, but sin()
+ expects its input in radians, so we multiply by 2 PI to convert it.
+ We also multiply by volume so it's not extremely loud. */
+ output[pos] = sin(self->phase * 2 * PI) * volume;
+
+ /* Increment the phase so we generate the next sample */
+ self->phase += phase_increment;
+ if (self->phase > 1.0f) {
+ self->phase = 0.0f;
+ }
+ }
+}
+
+/** Finish running (counterpart to activate()). */
+static void
+deactivate(LV2_Handle instance)
+{
+ /* Nothing to do here in this trivial mostly stateless plugin. */
+}
+
+/** Destroy a plugin instance (counterpart to instantiate()). */
+static void
+cleanup(LV2_Handle instance)
+{
+ free(instance);
+}
+
+/** Return extension data provided by the plugin. */
+const void*
+extension_data(const char* uri)
+{
+ return NULL; /* This plugin has no extension data. */
+}
+
+/** The LV2_Descriptor for this plugin. */
+static const LV2_Descriptor descriptor = {
+ SYNTH_URI,
+ instantiate,
+ connect_port,
+ activate,
+ run,
+ deactivate,
+ cleanup,
+ extension_data
+};
+
+/** Entry point, the host will call this function to access descriptors. */
+LV2_SYMBOL_EXPORT
+const LV2_Descriptor*
+lv2_descriptor(uint32_t index)
+{
+ switch (index) {
+ case 0:
+ return &descriptor;
+ default:
+ return NULL;
+ }
+}