/* LV2 - An audio plugin interface specification * Revision 4 * * Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis, * Stefan Westerfeld. * Copyright (C) 2006-2010 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 * 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. */ /** @file lv2.h * C header for the LV2 specification . * Revision: 4 */ #ifndef LV2_H_INCLUDED #define LV2_H_INCLUDED #include #ifdef __cplusplus 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. */ 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 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 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 , 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. */ 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 */