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authorDavid Robillard <d@drobilla.net>2008-01-09 02:25:46 +0000
committerDavid Robillard <d@drobilla.net>2008-01-09 02:25:46 +0000
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SLV2 0.4.2.
git-svn-id: http://svn.drobilla.net/lad/slv2@1040 a436a847-0d15-0410-975c-d299462d15a1
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-/* LV2 - LADSPA (Linux Audio Developer's Simple Plugin API) Version 2.0
- * *** PROVISIONAL Revision 1.0beta7 (2007-11-14) ***
- *
- * Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis,
- * Stefan Westerfeld.
- * Copyright (C) 2006-2007 Steve Harris, Dave 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
- * by the Free Software Foundation; either version 2.1 of the License,
- * or (at your option) any later version.
- *
- * This header is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
- * USA.
- */
-
-#ifndef LV2_H_INCLUDED
-#define LV2_H_INCLUDED
-
-#include <stdint.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-
-/* ************************************************************************* */
-
-
-/** @file lv2.h
- *
- * Revision: 1.0beta7
- *
- * == Overview ==
- *
- * There are a large number of open source and free software synthesis
- * packages in use or development at this time. This API ('LV2')
- * attempts to give programmers the ability to write simple 'plugin'
- * audio processors in C/C++ and link them dynamically ('plug') into
- * a range of these packages ('hosts'). It should be possible for any
- * host and any plugin to communicate completely through this interface.
- *
- * This API is deliberately as short and simple as possible.
- * The information required to use a plugin is in a companion data
- * (RDF) file. The shared library portion of the API (defined in this
- * header) does not contain enough information to make use of the plugin
- * possible - the data file is mandatory.
- *
- * Plugins are expected to distinguish between control rate and audio
- * rate data (or other types of data defined by extensions). Plugins have
- * 'ports' that are inputs or outputs and each plugin is 'run' for a 'block'
- * corresponding to a short time interval measured in samples. Audio rate
- * data is communicated using arrays with one element per sample processed,
- * allowing a block of audio to be processed by the plugin in a single
- * pass. Control rate data is communicated using single values. Control
- * rate data has a single value at the start of a call to the 'run()'
- * function, and may be considered to remain this value for its duration.
- * Thus the 'control rate' is determined by the block size, controlled by
- * the host. The plugin may assume that all its input and output ports have
- * been connected to the relevant data location (see the 'connect_port()'
- * function below) before it is asked to run, unless the port has been set
- * 'connection optional' in the plugin's data file.
- *
- * Plugins will reside in shared object files suitable for dynamic linking
- * by dlopen() and family. The file will provide a number of 'plugin
- * types' that can be used to instantiate actual plugins (sometimes known
- * as 'plugin instances') that can be connected together to perform tasks.
- * The host can access these plugin types using the lv2_descriptor()
- * function.
- *
- * This API contains very limited error-handling.
- *
- * == Threading rules ==
- *
- * Certain hosts may need to call the functions provided by a plugin from
- * multiple threads. For this to be safe, the plugin must be written so that
- * those functions can be executed simultaneously without problems.
- * To facilitate this, the functions provided by a plugin are divided into
- * classes:
- *
- * - Discovery class: lv2_descriptor(), extension_data()
- * - Instantiation class: instantiate(), cleanup(), activate(), deactivate()
- * - Audio class: run(), connect_port()
- *
- * Extensions to this specification which add new functions MUST declare in
- * which of these classes the functions belong, or define new classes for them.
- * The rules that hosts must follow are these:
- *
- * - When a function from the Discovery class is running, no other
- * functions in the same shared object file may run.
- * - When a function from the Instantiation class is running for a plugin
- * instance, no other functions for that instance may run.
- * - When a function is running for a plugin instance, no other
- * function in the same class may run for that instance.
- *
- * Any simultaneous calls that are not explicitly forbidden by these rules
- * are allowed. For example, a host may call run() for two different plugin
- * instances simultaneously.
- */
-
-
-/* ************************************************************************* */
-
-
-/** 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. */
-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. */
-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. */
- 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. */
- void * data;
-} LV2_Feature;
-
-
-/* ************************************************************************* */
-
-
-/** Descriptor for a Type of 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. */
-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. */
- 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. */
- 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). */
- 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(). */
- 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). */
- 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. */
- 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. */
- 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);
-
-} LV2_Descriptor;
-
-
-/* ****************************************************************** */
-
-
-/** Accessing Plugin Types.
- *
- * The exact mechanism by which plugins are loaded is host-dependent,
- * however all most hosts will need to know is the URI of the plugin they
- * wish to load. The environment variable LV2_PATH, if present, should
- * contain a colon-separated path indicating directories (containing
- * plugin bundle subdirectories) that should be searched (in order)
- * for plugins. It is expected that hosts will 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
- * the 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 (ie when serialising)
- * in any way. */
-const LV2_Descriptor * lv2_descriptor(uint32_t index);
-
-
-/** Datatype corresponding to the lv2_descriptor() function. */
-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.
- */
-#ifdef WIN32
-#define LV2_SYMBOL_EXPORT __declspec(dllexport)
-#else
-#define LV2_SYMBOL_EXPORT
-#endif
-
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* LV2_H_INCLUDED */
-