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-rw-r--r--plugins/eg-amp.lv2/amp.c117
1 files changed, 95 insertions, 22 deletions
diff --git a/plugins/eg-amp.lv2/amp.c b/plugins/eg-amp.lv2/amp.c
index 86f7a81..8dd7b4f 100644
--- a/plugins/eg-amp.lv2/amp.c
+++ b/plugins/eg-amp.lv2/amp.c
@@ -15,30 +15,43 @@
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
-/**
- @file amp.c Implementation of the LV2 Amp example plugin.
-
- This is a basic working LV2 plugin, about as small as one can get. It is
- useful as a skeleton to copy to build more advanced plugins. See lv2.h for
- more detailed descriptions of the rules for the various functions.
-*/
-
+/** Include standard C headers */
#include <math.h>
#include <stdlib.h>
-#include <string.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"
-/** Port indices. */
+/**
+ 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;
-/** Plugin instance. */
+/**
+ 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;
@@ -46,7 +59,16 @@ typedef struct {
float* output;
} Amp;
-/** Create a new plugin instance. */
+/**
+ 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,
@@ -58,7 +80,14 @@ instantiate(const LV2_Descriptor* descriptor,
return (LV2_Handle)amp;
}
-/** Connect a port to a buffer (audio thread, must be RT safe). */
+/**
+ 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,
@@ -79,13 +108,21 @@ connect_port(LV2_Handle instance,
}
}
-/** Initialise and prepare the plugin instance for running. */
+/**
+ 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)
{
- /* Nothing to do here in this trivial mostly stateless plugin. */
}
+/** 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). */
@@ -105,28 +142,55 @@ run(LV2_Handle instance, uint32_t n_samples)
}
}
-/** Finish running (counterpart to activate()). */
+/**
+ 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)
{
- /* Nothing to do here in this trivial mostly stateless plugin. */
}
-/** Destroy a plugin instance (counterpart to instantiate()). */
+/**
+ 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);
}
-/** Return extension data provided by the plugin. */
+/**
+ 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; /* This plugin has no extension data. */
+ return NULL;
}
-/** The LV2_Descriptor for this plugin. */
+/**
+ 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,
@@ -138,7 +202,16 @@ static const LV2_Descriptor descriptor = {
extension_data
};
-/** Entry point, the host will call this function to access descriptors. */
+/**
+ 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)