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authorDavid Robillard <d@drobilla.net>2011-03-01 04:09:49 +0000
committerDavid Robillard <d@drobilla.net>2011-03-01 04:09:49 +0000
commitdcc2cf3b1754304a5bb269b6dda9b06c89708e42 (patch)
treee21fa22a225dc0d6c662a8cf43325c404d55fc42 /core.lv2/lv2.h
parent34d3a9631e76bf99627b50c18edcf4833638f926 (diff)
downloadlv2-dcc2cf3b1754304a5bb269b6dda9b06c89708e42.tar.xz
Update lv2.h documentation.
Diffstat (limited to 'core.lv2/lv2.h')
-rw-r--r--core.lv2/lv2.h468
1 files changed, 244 insertions, 224 deletions
diff --git a/core.lv2/lv2.h b/core.lv2/lv2.h
index f1758cf..4f41bde 100644
--- a/core.lv2/lv2.h
+++ b/core.lv2/lv2.h
@@ -3,7 +3,7 @@
*
* Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis,
* Stefan Westerfeld.
- * Copyright (C) 2006-2010 Steve Harris, David Robillard.
+ * Copyright (C) 2006-2011 Steve Harris, David Robillard.
*
* This header is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published
@@ -21,10 +21,11 @@
* USA.
*/
-/** @file lv2.h
- * C header for the LV2 specification <http://lv2plug.in/ns/lv2core>.
- * Revision: 4
- */
+/**
+ @file lv2.h
+ API for the LV2 specification <http://lv2plug.in/ns/lv2core>.
+ Revision: 4
+*/
#ifndef LV2_H_INCLUDED
#define LV2_H_INCLUDED
@@ -35,269 +36,288 @@
extern "C" {
#endif
-
-/** Plugin Handle.
- *
- * This plugin handle indicates a particular instance of the plugin
- * concerned. It is valid to compare this to NULL (0 for C++) but
- * otherwise the host MUST NOT attempt to interpret it. The plugin
- * may use it to reference internal instance data. */
+/**
+ Plugin Handle.
+
+ This handle refers to a particular instance of a plugin. It is valid to
+ compare to NULL (or 0 for C++) but otherwise the host MUST NOT attempt to
+ interpret it. The plugin may use it to reference internal instance data.
+*/
typedef void * LV2_Handle;
-
-/** Feature data.
- *
- * These are passed to a plugin's instantiate method to represent a special
- * feature the host has which the plugin may depend on. This is to allow
- * extensions to the LV2 specification without causing any breakage.
- * Extensions may specify what data needs to be passed here. The base
- * LV2 specification does not define any features; hosts are not required
- * to use this facility. */
+/**
+ Feature data.
+
+ These are passed to a plugin's instantiate method to represent a special
+ feature the host has which the plugin may depend on. This allows extensions
+ to the plugin interface without breaking the LV2 API. Extensions that
+ describe a feature MUST specify the @a URI and format of @a data that needs
+ to be used here. The core LV2 specification does not define any features;
+ hosts are not required to use this facility.
+*/
typedef struct _LV2_Feature {
-
- /** A globally unique, case-sensitive identifier for this feature.
- *
- * This MUST be defined in the specification of any LV2 extension which
- * defines a host feature. */
+ /**
+ A globally unique, case-sensitive identifier (URI) for this feature.
+ */
const char * URI;
- /** Pointer to arbitrary data.
- *
- * This is to allow hosts to pass data to a plugin (simple values, data
- * structures, function pointers, etc) as part of a 'feature'. The LV2
- * specification makes no restrictions on the contents of this data.
- * The data here MUST be cleary defined by the LV2 extension which defines
- * this feature.
- * If no data is required, this may be set to NULL. */
+ /**
+ Pointer to arbitrary data.
+
+ The format of this data is defined by the extension which describes the
+ feature with the given @a URI. The core LV2 specification makes no
+ restrictions on the format of this data. If no data is required, this
+ may be set to NULL if the relevant extension explicitly allows this.
+ */
void * data;
-
} LV2_Feature;
-
-/** Descriptor for a Plugin.
- *
- * This structure is used to describe a plugin type. It provides a number
- * of functions to instantiate it, link it to buffers and run it. */
+/**
+ Descriptor for an LV2 Plugin.
+
+ This structure is used to describe a plugin. It provides the functions
+ necessary to instantiate and use a plugin.
+*/
typedef struct _LV2_Descriptor {
-
- /** A globally unique, case-sensitive identifier for this plugin type.
- *
- * All plugins with the same URI MUST be compatible in terms of 'port
- * signature', meaning they have the same number of ports, same port
- * shortnames, and roughly the same functionality. URIs should
- * probably contain a version number (or similar) for this reason.
- *
- * Rationale: When serializing session/patch/etc files, hosts MUST
- * refer to a loaded plugin by the plugin URI only. In the future
- * loading a plugin with this URI MUST yield a plugin with the
- * same ports (etc) which is 100% compatible. */
+ /**
+ A globally unique, case-sensitive identifier for this plugin type.
+
+ All plugins with the same URI MUST be compatible in terms of 'port
+ signature', meaning they have the same ports with the same symbols.
+ Newer versions of a plugin MAY be released with the same URI if ports are
+ added, as long as all such ports are "connection optional". shortnames,
+ and roughly the same functionality. Newer versions of a plugin that
+ break these rules MUST have a different URI, e.g. by appending a version
+ number to the previous URI.
+
+ When referring to plugins in a persistent serialisation (e.g. session or
+ patch files, network protocols, etc.), hosts MUST refer to a loaded
+ plugin by URI only. The rules above are designed such that, in the future,
+ loading a plugin with this URI will yield a plugin which can be used
+ identically (i.e. has identical ports) (though the plugin MAY be a newer
+ revision with additional "connection optional" ports.
+ */
const char * URI;
- /** Function pointer that instantiates a plugin.
- *
- * A handle is returned indicating the new plugin instance. The
- * instantiation function accepts a sample rate as a parameter as well
- * as the plugin descriptor from which this instantiate function was
- * found. This function must return NULL if instantiation fails.
- *
- * bundle_path is a string of the path to the LV2 bundle which contains
- * this plugin binary. It MUST include the trailing directory separator
- * (e.g. '/') so that BundlePath + filename gives the path to a file
- * in the bundle.
- *
- * features is a NULL terminated array of LV2_Feature structs which
- * represent the features the host supports. Plugins may refuse to
- * instantiate if required features are not found here (however hosts
- * SHOULD NOT use this as a discovery mechanism, instead reading the
- * data file before attempting to instantiate the plugin). This array
- * must always exist; if a host has no features, it MUST pass a single
- * element array containing NULL (to simplify plugins).
- *
- * Note that instance initialisation should generally occur in
- * activate() rather than here. If a host calls instantiate, it MUST
- * call cleanup() at some point in the future. */
+ /**
+ Instantiate the plugin.
+
+ Note that instance initialisation should generally occur in activate()
+ rather than here. If a host calls instantiate, it MUST call cleanup()
+ at some point in the future.
+
+ @param descriptor Descriptor of the plugin to instantiate.
+
+ @param sample_rate Sample rate, in Hz, for the new plugin instance.
+
+ @param bundle_path Path to the LV2 bundle which contains this plugin
+ binary. It MUST include the trailing directory separator (e.g. '/') so
+ that simply appending a filename will give the full path to that file in
+ the bundle.
+
+ @param features A NULL terminated array of LV2_Feature structs which
+ represent the features the host supports. Plugins may refuse to
+ instantiate if required features are not found here. However, hosts MUST
+ NOT use this as a discovery mechanism: instead, use the data file to
+ determinate what features are required, and do not attempt to load or
+ instantiate unsupported plugins at all. This parameter MUST NOT be NULL,
+ i.e. a host that supports no features MUST pass a single element array
+ containing NULL.
+
+ @return A handle for the new plugin instance, or NULL if instantiation
+ has failed.
+ */
LV2_Handle (*instantiate)(const struct _LV2_Descriptor * descriptor,
double sample_rate,
const char * bundle_path,
const LV2_Feature *const * features);
- /** Function pointer that connects a port on a plugin instance to a memory
- * location where the block of data for the port will be read/written.
- *
- * The data location is expected to be of the type defined in the
- * plugin's data file (e.g. an array of float for an lv2:AudioPort).
- * Memory issues are managed by the host. The plugin must read/write
- * the data at these locations every time run() is called, data
- * present at the time of this connection call MUST NOT be
- * considered meaningful.
- *
- * The host MUST NOT try to connect a data buffer to a port index
- * that is not defined in the RDF data for the plugin. If it does,
- * the plugin's behaviour is undefined.
- *
- * connect_port() may be called more than once for a plugin instance
- * to allow the host to change the buffers that the plugin is reading
- * or writing. These calls may be made before or after activate()
- * or deactivate() calls. Note that there may be realtime constraints
- * on connect_port (see lv2:hardRTCapable in lv2.ttl).
- *
- * connect_port() MUST be called at least once for each port before
- * run() is called. The plugin must pay careful attention to the block
- * size passed to the run function as the block allocated may only just
- * be large enough to contain the block of data (typically samples), and
- * is not guaranteed to be constant.
- *
- * Plugin writers should be aware that the host may elect to use the
- * same buffer for more than one port and even use the same buffer for
- * both input and output (see lv2:inPlaceBroken in lv2.ttl).
- * However, overlapped buffers or use of a single buffer for both
- * audio and control data may result in unexpected behaviour.
- *
- * If the plugin has the feature lv2:hardRTCapable then there are
- * various things that the plugin MUST NOT do within the connect_port()
- * function (see lv2.ttl). */
+ /**
+ Connect a port on a plugin instance to a memory location.
+
+ Plugin writers should be aware that the host may elect to use the same
+ buffer for more than one port and even use the same buffer for both
+ input and output (see lv2:inPlaceBroken in lv2.ttl). However,
+ overlapped buffers or use of a single buffer for both audio and control
+ data may result in unexpected behaviour.
+
+ If the plugin has the feature lv2:hardRTCapable then there are various
+ things that the plugin MUST NOT do within the connect_port() function
+ (see lv2.ttl).
+
+ connect_port() MUST be called at least once for each port before run()
+ is called, unless that port is lv2:connectionOptional. The plugin must
+ pay careful attention to the block size passed to the run function as
+ the block allocated may only just be large enough to contain the block
+ of data (typically samples), and is not guaranteed to be constant.
+
+ connect_port() may be called more than once for a plugin instance to
+ allow the host to change the buffers that the plugin is reading or
+ writing. These calls may be made before or after activate() or
+ deactivate() calls.
+
+ @param instance Plugin instance containing the port.
+
+ @param port Index of the port to connect. The host MUST NOT try to
+ connect a port index that is not defined in the plugin's RDF data. If
+ it does, the plugin's behaviour is undefined (a crash is likely).
+
+ @param data_location Pointer to data of the type defined by the port
+ type in the plugin's data file (e.g. an array of float for an
+ lv2:AudioPort). This pointer must be stored by the plugin instance and
+ used to read/write data when run() is called. Data present at the time
+ of the connect_port() call MUST NOT be considered meaningful.
+ */
void (*connect_port)(LV2_Handle instance,
uint32_t port,
void * data_location);
- /** Function pointer that initialises a plugin instance and activates
- * it for use.
- *
- * This is separated from instantiate() to aid real-time support and so
- * that hosts can reinitialise a plugin instance by calling deactivate()
- * and then activate(). In this case the plugin instance must reset all
- * state information dependent on the history of the plugin instance
- * except for any data locations provided by connect_port(). If there
- * is nothing for activate() to do then the plugin writer may provide
- * a NULL rather than an empty function.
- *
- * When present, hosts MUST call this function once before run()
- * is called for the first time. This call SHOULD be made as close
- * to the run() call as possible and indicates to real-time plugins
- * that they are now live, however plugins MUST NOT rely on a prompt
- * call to run() after activate(). activate() may not be called again
- * unless deactivate() is called first (after which activate() may be
- * called again, followed by deactivate, etc. etc.). If a host calls
- * activate, it MUST call deactivate at some point in the future.
- *
- * Note that connect_port() may be called before or after a call to
- * activate(). */
+ /**
+ Initialise a plugin instance and activate it for use.
+
+ This is separated from instantiate() to aid real-time support and so
+ that hosts can reinitialise a plugin instance by calling deactivate()
+ and then activate(). In this case the plugin instance MUST reset all
+ state information dependent on the history of the plugin instance except
+ for any data locations provided by connect_port(). If there is nothing
+ for activate() to do then this field may be NULL.
+
+ When present, hosts MUST call this function once before run() is called
+ for the first time. This call SHOULD be made as close to the run() call
+ as possible and indicates to real-time plugins that they are now live,
+ however plugins MUST NOT rely on a prompt call to run() after
+ activate().
+
+ The host MUST NOT call activate() again until deactivate() has been
+ called first. If a host calls activate(), it MUST call deactivate() at
+ some point in the future. Note that connect_port() may be called before
+ or after activate().
+ */
void (*activate)(LV2_Handle instance);
- /** Function pointer that runs a plugin instance for a block.
- *
- * Two parameters are required: the first is a handle to the particular
- * instance to be run and the second indicates the block size (in
- * samples) for which the plugin instance may run.
- *
- * Note that if an activate() function exists then it must be called
- * before run(). If deactivate() is called for a plugin instance then
- * the plugin instance may not be reused until activate() has been
- * called again.
- *
- * If the plugin has the feature lv2:hardRTCapable then there are
- * various things that the plugin MUST NOT do within the run()
- * function (see lv2.ttl). */
+ /**
+ Runs a plugin instance for a block.
+
+ Note that if an activate() function exists then it must be called before
+ run(). If deactivate() is called for a plugin instance then run() may
+ not be called until activate() has been called again.
+
+ If the plugin has the feature lv2:hardRTCapable then there are
+ various things that the plugin MUST NOT do within the run()
+ function (see lv2.ttl for details).
+
+ @param instance Instance to be run.
+
+ @param sample_count The block size (in samples) for which the plugin
+ instance must run.
+ */
void (*run)(LV2_Handle instance,
uint32_t sample_count);
- /** This is the counterpart to activate() (see above). If there is
- * nothing for deactivate() to do then the plugin writer may provide
- * a NULL rather than an empty function.
- *
- * Hosts must deactivate all activated units after they have been run()
- * for the last time. This call SHOULD be made as close to the last
- * run() call as possible and indicates to real-time plugins that
- * they are no longer live, however plugins MUST NOT rely on prompt
- * deactivation. Note that connect_port() may be called before or
- * after a call to deactivate().
- *
- * Note that deactivation is not similar to pausing as the plugin
- * instance will be reinitialised when activate() is called to reuse it.
- * Hosts MUST NOT call deactivate() unless activate() was previously
- * called. */
+ /**
+ Deactivate a plugin instance (counterpart to activate()).
+
+ Hosts MUST deactivate all activated instances after they have been run()
+ for the last time. This call SHOULD be made as close to the last run()
+ call as possible and indicates to real-time plugins that they are no
+ longer live, however plugins MUST NOT rely on prompt deactivation. If
+ there is nothing for deactivate() to do then this field may be NULL
+
+ Deactivation is not similar to pausing since the plugin instance will be
+ reinitialised by activate(). However, deactivate() itself MUST NOT fully
+ reset plugin state. For example, the host may deactivate a plugin, then
+ store its state (using some extension to do so).
+
+ Hosts MUST NOT call deactivate() unless activate() was previously
+ called. Note that connect_port() may be called before or after
+ deactivate().
+ */
void (*deactivate)(LV2_Handle instance);
- /** This is the counterpart to instantiate() (see above). Once an instance
- * of a plugin has been finished with it can be deleted using this
- * function. The instance handle passed ceases to be valid after
- * this call.
- *
- * If activate() was called for a plugin instance then a corresponding
- * call to deactivate() MUST be made before cleanup() is called.
- * Hosts MUST NOT call cleanup() unless instantiate() was previously
- * called. */
+ /**
+ Clean up a plugin instance (counterpart to instantiate()).
+
+ Once an instance of a plugin has been finished with it must be deleted
+ using this function. The instance handle passed ceases to be valid after
+ this call.
+
+ If activate() was called for a plugin instance then a corresponding call
+ to deactivate() MUST be made before cleanup() is called. Hosts MUST NOT
+ call cleanup() unless instantiate() was previously called.
+ */
void (*cleanup)(LV2_Handle instance);
- /** Function pointer that can be used to return additional instance data for
- * a plugin defined by some extenion (e.g. a struct containing additional
- * function pointers).
- *
- * The actual type and meaning of the returned object MUST be specified
- * precisely by the extension if it defines any extra data. If a particular
- * extension does not define extra instance data, this function MUST return
- * NULL for that extension's URI. If a plugin does not support any
- * extensions that define extra instance data, this function pointer may be
- * set to NULL rather than providing an empty function.
- *
- * The only parameter is the URI of the extension. The plugin MUST return
- * NULL if it does not support the extension, but hosts SHOULD NOT use this
- * as a discovery method (e.g. hosts should only call this function for
- * extensions known to be supported by the plugin from the data file).
- *
- * The host is never responsible for freeing the returned value.
- *
- * NOTE: This function should return a struct (likely containing function
- * pointers) and NOT a direct function pointer. Standard C and C++ do not
- * allow type casts from void* to a function pointer type. To provide
- * additional functions a struct should be returned containing the extra
- * function pointers (which is valid standard code, and a much better idea
- * for extensibility anyway). */
- const void* (*extension_data)(const char * uri);
+ /**
+ Return additional plugin data defined by some extenion.
+ A typical use of this facility is to return a struct containing function
+ pointers to extend the LV2_Descriptor API.
+
+ The actual type and meaning of the returned object MUST be specified
+ precisely by the extension if it defines any extra data. This function
+ MUST return NULL for any unsupported URI. If a plugin does not support any
+ extensions that define extra data, this field may be NULL.
+
+ @param uri URI of the extension. The plugin MUST return NULL if it does
+ not support the extension, but hosts MUST NOT use this as a discovery
+ mechanism. Hosts should only call this function for extensions known to
+ be supported by the plugin, as described in the plugin's data file.
+
+ The host is never responsible for freeing the returned value.
+
+ Note this function SHOULD return a struct (likely containing function
+ pointers) and NOT a direct function pointer. Standard C and C++ do not
+ allow type casts from void* to a function pointer type, and returning a
+ struct is much better since it is extensible (e.g. fields can be added
+ by backwards compatible extensions).
+ */
+ const void * (*extension_data)(const char * uri);
} LV2_Descriptor;
+/**
+ Prototype for plugin accessor function.
+
+ The exact mechanism by which plugin libraries are loaded is host and system
+ dependent, however all hosts need to know is the URI of the plugin they wish
+ to load. Plugins are discovered via data files (not by loading libraries).
+ Documentation on best practices for plugin discovery can be found at
+ <http://lv2plug.in>, however it is expected that hosts use a library to
+ provide this functionality.
+
+ A plugin library MUST include a function called "lv2_descriptor" with this
+ prototype. This function MUST have C-style linkage (if you are using C++
+ this is taken care of by the 'extern "C"' clause at the top of this file).
+
+ A host will find the plugin's library via data files, get the
+ lv2_descriptor() function from it, and proceed from there.
+
+ Plugins are accessed by index using values from 0 upwards. Out of range
+ indices MUST result in this function returning NULL, so the host can
+ enumerate plugins by increasing @a index until NULL is returned.
-/** Accessing Plugins.
- *
- * The exact mechanism by which plugins are loaded is host and system
- * dependent, however all hosts need to know is the URI of the plugin they
- * wish to load. Documentation on best practices for plugin discovery can
- * be found at <http://lv2plug.in>, however it is expected that hosts use
- * a library to provide this functionality.
- *
- * A plugin programmer MUST include a function called "lv2_descriptor"
- * with the following function prototype within the shared object
- * file. This function will have C-style linkage (if you are using
- * C++ this is taken care of by the 'extern "C"' clause at the top of
- * this file).
- *
- * A host will find the plugin shared object file by one means or another,
- * find the lv2_descriptor() function, call it, and proceed from there.
- *
- * Plugin types are accessed by index (not ID) using values from 0
- * upwards. Out of range indexes MUST result in this function returning
- * NULL, so the plugin count can be determined by checking for the least
- * index that results in NULL being returned. Index has no meaning,
- * hosts MUST NOT depend on it remaining constant (e.g. when serialising)
- * in any way. */
+ Note that @a index has no meaning, hosts MUST NOT depend on it remaining
+ constant in any way. In particular, hosts MUST NOT refer to plugins by
+ library path and index in persistent serialisations (e.g. save files).
+ In other words, the index is NOT a plugin ID.
+*/
const LV2_Descriptor * lv2_descriptor(uint32_t index);
-
-/** Datatype corresponding to the lv2_descriptor() function. */
+/**
+ Type of the lv2_descriptor() function in a plugin library.
+*/
typedef const LV2_Descriptor *
(*LV2_Descriptor_Function)(uint32_t index);
-
-/* Put this (LV2_SYMBOL_EXPORT) before any functions that are to be loaded
- * by the host as a symbol from the dynamic library. */
+/**
+ Put this (LV2_SYMBOL_EXPORT) before any functions that are to be loaded
+ by the host as a symbol from the dynamic library.
+*/
#ifdef WIN32
#define LV2_SYMBOL_EXPORT __declspec(dllexport)
#else
#define LV2_SYMBOL_EXPORT
#endif
-
#ifdef __cplusplus
}
#endif