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+/*
+ Copyright 2006-2011 David Robillard <d@drobilla.net>
+ Copyright 2006 Steve Harris <steve@plugin.org.uk>
+
+ 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 standard C headers */
+#include <math.h>
+#include <stdlib.h>
+
+/**
+ LV2 headers are based on the URI of the specification they come from, so a
+ consistent convention can be used even for unofficial extensions. The URI
+ of the core LV2 specification is <http://lv2plug.in/ns/lv2core>, by
+ replacing `http:/` with `lv2` any header in the specification bundle can be
+ included, in this case `lv2.h`.
+*/
+#include "lv2/lv2plug.in/ns/lv2core/lv2.h"
+
+/**
+ The URI is the identifier for a plugin, and how the host associates this
+ implementation in code with its description in data. In this plugin it is
+ only used once in the code, but defining the plugin URI at the top of the
+ file is a good convention to follow. If this URI does not match that used
+ in the data files, the host will fail to load the plugin.
+*/
+#define AMP_URI "http://lv2plug.in/plugins/eg-amp"
+
+/**
+ In code, ports are referred to by index. An enumeration of port indices
+ should be defined for readability.
+*/
+typedef enum {
+ AMP_GAIN = 0,
+ AMP_INPUT = 1,
+ AMP_OUTPUT = 2
+} PortIndex;
+
+/**
+ Every plugin defines a private structure for the plugin instance. All data
+ associated with a plugin instance is stored here, and is available to
+ every instance method. In this simple plugin, only port buffers need to be
+ stored, since there is no additional instance data. */
+typedef struct {
+ // Port buffers
+ const float* gain;
+ const float* input;
+ float* output;
+} Amp;
+
+/**
+ The instantiate() function is called by the host to create a new plugin
+ instance. The host passes the plugin descriptor, sample rate, and bundle
+ path for plugins that need to load additional resources (e.g. waveforms).
+ The features parameter contains host-provided features defined in LV2
+ extensions, but this simple plugin does not use any.
+
+ This function is in the ``instantiation'' threading class, so no other
+ methods on this instance will be called concurrently with it.
+*/
+static LV2_Handle
+instantiate(const LV2_Descriptor* descriptor,
+ double rate,
+ const char* bundle_path,
+ const LV2_Feature* const* features)
+{
+ Amp* amp = (Amp*)malloc(sizeof(Amp));
+
+ return (LV2_Handle)amp;
+}
+
+/**
+ The connect_port() method is called by the host to connect a particular port
+ to a buffer. The plugin must store the data location, but data may not be
+ accessed except in run().
+
+ This method is in the ``audio'' threading class, and is called in the same
+ context as run().
+*/
+static void
+connect_port(LV2_Handle instance,
+ uint32_t port,
+ void* data)
+{
+ Amp* amp = (Amp*)instance;
+
+ switch ((PortIndex)port) {
+ case AMP_GAIN:
+ amp->gain = (const float*)data;
+ break;
+ case AMP_INPUT:
+ amp->input = (const float*)data;
+ break;
+ case AMP_OUTPUT:
+ amp->output = (float*)data;
+ break;
+ }
+}
+
+/**
+ The activate() method is called by the host to initialise and prepare the
+ plugin instance for running. The plugin must reset all internal state
+ except for buffer locations set by connect_port(). Since this plugin has
+ no other internal state, this method does nothing.
+
+ This method is in the ``instantiation'' threading class, so no other
+ methods on this instance will be called concurrently with it.
+*/
+static void
+activate(LV2_Handle instance)
+{
+}
+
+/** Define a macro for converting a gain in dB to a coefficient */
+#define DB_CO(g) ((g) > -90.0f ? powf(10.0f, (g) * 0.05f) : 0.0f)
+
+/** Process a block of audio (audio thread, must be RT safe). */
+static void
+run(LV2_Handle instance, uint32_t n_samples)
+{
+ const Amp* amp = (const Amp*)instance;
+
+ const float gain = *(amp->gain);
+ const float* const input = amp->input;
+ float* const output = amp->output;
+
+ const float coef = DB_CO(gain);
+
+ for (uint32_t pos = 0; pos < n_samples; pos++) {
+ output[pos] = input[pos] * coef;
+ }
+}
+
+/**
+ The deactivate() method is the counterpart to activate() called by the host
+ after running the plugin. It indicates that the host will not call run()
+ again until another call to activate() and is mainly useful for more
+ advanced plugins with ``live'' characteristics such as those with auxiliary
+ processing threads. As with activate(), this plugin has no use for this
+ information so this method does nothing.
+
+ This method is in the ``instantiation'' threading class, so no other
+ methods on this instance will be called concurrently with it.
+*/
+static void
+deactivate(LV2_Handle instance)
+{
+}
+
+/**
+ Destroy a plugin instance (counterpart to instantiate()).
+
+ This method is in the ``instantiation'' threading class, so no other
+ methods on this instance will be called concurrently with it.
+*/
+static void
+cleanup(LV2_Handle instance)
+{
+ free(instance);
+}
+
+/**
+ The extension_data function returns any extension data supported by the
+ plugin. Note that this is not an instance method, but a function on the
+ plugin descriptor. It is usually used by plugins to implement additional
+ interfaces. This plugin does not have any extension data, so this function
+ returns NULL.
+
+ This method is in the ``discovery'' threading class, so no other functions
+ or methods in this plugin library will be called concurrently with it.
+*/
+static const void*
+extension_data(const char* uri)
+{
+ return NULL;
+}
+
+/**
+ Define the LV2_Descriptor for this plugin. It is best to define descriptors
+ statically to avoid leaking memory and non-portable shared library
+ constructors and destructors to clean up properly.
+*/
+static const LV2_Descriptor descriptor = {
+ AMP_URI,
+ instantiate,
+ connect_port,
+ activate,
+ run,
+ deactivate,
+ cleanup,
+ extension_data
+};
+
+/**
+ The lv2_descriptor() function is the entry point to the plugin library. The
+ host will load the library and call this function repeatedly with increasing
+ indices to find all the plugins defined in the library. The index is not an
+ indentifier, the URI of the returned descriptor is used to determine the
+ identify of the plugin.
+
+ This method is in the ``discovery'' threading class, so no other functions
+ or methods in this plugin library will be called concurrently with it.
+*/
+LV2_SYMBOL_EXPORT
+const LV2_Descriptor*
+lv2_descriptor(uint32_t index)
+{
+ switch (index) {
+ case 0:
+ return &descriptor;
+ default:
+ return NULL;
+ }
+}