306 lines
13 KiB
C
306 lines
13 KiB
C
/* LV2 - LADSPA (Linux Audio Developer's Simple Plugin API) Version 2.0
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* *** PROVISIONAL ***
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*
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* Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis, Stefan
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* Westerfeld
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* Copyright (C) 2006 Steve Harris, Dave Robillard.
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*
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* This header is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published
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* by the Free Software Foundation; either version 2.1 of the License,
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* or (at your option) any later version.
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*
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* This header is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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* USA.
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*/
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#ifndef LV2_INCLUDED
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#define LV2_INCLUDED
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* ************************************************************************* */
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/* Overview:
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*
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* There are a large number of open source and free software synthesis
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* packages in use or development at this time. This API ('LV2')
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* attempts to give programmers the ability to write simple 'plugin'
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* audio processors in C/C++ and link them dynamically ('plug') into
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* a range of these packages ('hosts'). It should be possible for any
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* host and any plugin to communicate completely through this interface.
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*
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* This API is deliberately as short and simple as possible.
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* The information required to use a plugin is in a companion data
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* (RDF) file. The shared library portion of the API (defined in this
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* header) does not contain enough information to make use of the plugin
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* possible - the data file is mandatory.
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*
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* Plugins are expected to distinguish between control rate and audio
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* rate data. Plugins have 'ports' that are inputs or outputs for audio
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* or control data and each plugin is 'run' for a 'block' corresponding
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* to a short time interval measured in samples. Audio rate data is
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* communicated using arrays with one element per sample processed,
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* allowing a block of audio to be processed by the plugin in a single
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* pass. Control rate data is communicated using single values. Control
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* rate data has a single value at the start of a call to the 'run()'
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* function, and may be considered to remain this value for its duration.
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* Thus the 'control rate' is determined by the block size, controlled
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* by the host. The plugin may assume that all its input and output
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* ports have been connected to the relevant data location (see the
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* 'connect_port()' function below) before it is asked to run.
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*
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* Plugins will reside in shared object files suitable for dynamic linking
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* by dlopen() and family. The file will provide a number of 'plugin
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* types' that can be used to instantiate actual plugins (sometimes known
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* as 'plugin instances') that can be connected together to perform tasks.
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*
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* This API contains very limited error-handling.
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*/
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/* ************************************************************************* */
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/** Plugin Handle.
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*
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* This plugin handle indicates a particular instance of the plugin
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* concerned. It is valid to compare this to NULL (0 for C++) but
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* otherwise the host MUST not attempt to interpret it. The plugin
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* may use it to reference internal instance data. */
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typedef void * LV2_Handle;
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/* ************************************************************************* */
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/** Host feature.
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*
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* These are passed to a plugin's instantiate method to represent a special
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* feature the host has which the plugin may depend on. This is to allow
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* extensions to the LV2 specification without causing any breakage. The base
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* LV2 specification does not define any host features; hosts are not required
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* to use this facility.
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*/
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typedef struct _LV2_Host_Feature {
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/** A globally unique, case-sensitive identifier for this feature.
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*
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* This MUST be defined in the specification of any LV2 extension which
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* defines a host feature.
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*/
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const char * URI;
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/** Pointer to arbitrary data.
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*
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* This is to allow hosts to pass data to a plugin (simple values, data
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* structures, function pointers, etc) as part of a 'feature'. The LV2
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* specification makes no restrictions on the contents of this data.
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* The data here MUST be cleary defined by the LV2 extension which defines
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* this feature.
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* If no data is required, this may be set to NULL.
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*/
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void * data;
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} LV2_Host_Feature;
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/* ************************************************************************* */
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/** Descriptor for a Type of Plugin.
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*
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* This structure is used to describe a plugin type. It provides a number
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* of functions to instantiate it, link it to buffers and run it. */
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typedef struct _LV2_Descriptor {
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/** A globally unique, case-sensitive identifier for this plugin type.
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*
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* All plugins with the same URI MUST be compatible in terms of 'port
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* signature', meaning they have the same number of ports, same port
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* shortnames, and roughly the same functionality. URIs should
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* probably contain a version number (or similar) for this reason.
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*
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* Rationale: When serializing session/patch/etc files, hosts MUST
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* refer to a loaded plugin by the plugin URI only. In the future
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* loading a plugin with this URI MUST yield a plugin with the
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* same ports (etc) which is 100% compatible. */
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const char * URI;
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/** Function pointer that instantiates a plugin.
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*
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* A handle is returned indicating the new plugin instance. The
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* instantiation function accepts a sample rate as a parameter as well
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* as the plugin descriptor from which this instantiate function was
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* found. This function must return NULL if instantiation fails.
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*
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* BundlePath is a string of the path to the plugin's .lv2 bundle
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* directory, it MUST not include the trailing /.
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*
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* HostFeatures is a NULL terminated array of the URIs of the LV2
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* features that the host supports. Plugins may refuse to instantiate
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* if required features are not found here (however hosts SHOULD NOT use
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* this as a discovery mechanism, instead reading the data file before
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* attempting to instantiate the plugin).
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*
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* Note that instance initialisation should generally occur in
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* activate() rather than here. If a host calls instantiate, it MUST
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* call cleanup() at some point in the future. */
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LV2_Handle (*instantiate)(const struct _LV2_Descriptor * Descriptor,
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unsigned long SampleRate,
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const char * BundlePath,
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const LV2_Host_Feature** HostFeatures);
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/** Function pointer that connects a port on a plugin instance to a memory
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* location where the block of data for the port will be read/written.
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*
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* The data location is expected to be an array of void * (typically
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* float *) for audio ports or a single void * value for control
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* ports. Memory issues are managed by the host. The plugin must
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* read/write the data at these locations every time run() is called
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* and the data present at the time of this connection call MUST NOT
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* be considered meaningful.
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*
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* connect_port() may be called more than once for a plugin instance
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* to allow the host to change the buffers that the plugin is reading
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* or writing. These calls may be made before or after activate()
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* or deactivate() calls.
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*
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* connect_port() must be called at least once for each port before
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* run() is called. The plugin must pay careful attention to the block
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* size passed to the run function as the block allocated may only just
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* be large enough to contain the block of data (typically samples), and
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* is not guaranteed to be constant.
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*
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* Plugin writers should be aware that the host may elect to use the
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* same buffer for more than one port and even use the same buffer for
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* both input and output (see LV2_PROPERTY_INPLACE_BROKEN (FIXME)).
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* However, overlapped buffers or use of a single buffer for both
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* audio and control data may result in unexpected behaviour. */
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void (*connect_port)(LV2_Handle Instance,
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unsigned long Port,
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void * DataLocation);
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/** Function pointer that initialises a plugin instance and activates
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* it for use.
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*
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* This is separated from instantiate() to aid real-time support and so
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* that hosts can reinitialise a plugin instance by calling deactivate()
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* and then activate(). In this case the plugin instance must reset all
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* state information dependent on the history of the plugin instance
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* except for any data locations provided by connect_port(). If there
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* is nothing for activate() to do then the plugin writer may provide
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* a NULL rather than an empty function.
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*
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* When present, hosts MUST call this function once before run()
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* is called for the first time. This call SHOULD be made as close
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* to the run() call as possible and indicates to real-time plugins
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* that they are now live, however plugins MUST NOT rely on a prompt
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* call to run() after activate(). activate() may not be called again
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* unless deactivate() is called first (after which activate() may be
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* called again, followed by deactivate, etc. etc.). If a host calls
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* activate, it MUST call deactivate at some point in the future.
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*
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* Note that connect_port() may be called before or after a call to
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* activate(). */
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void (*activate)(LV2_Handle Instance);
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/** Function pointer that runs a plugin instance for a block.
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*
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* Two parameters are required: the first is a handle to the particular
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* instance to be run and the second indicates the block size (in
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* samples) for which the plugin instance may run.
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*
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* Note that if an activate() function exists then it must be called
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* before run(). If deactivate() is called for a plugin instance then
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* the plugin instance may not be reused until activate() has been
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* called again.
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*
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* If the plugin has the property LV2_PROPERTY_HARD_RT_CAPABLE then
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* there are various things that the plugin MUST NOT do within the run()
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* function (see above). */
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void (*run)(LV2_Handle Instance,
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unsigned long SampleCount);
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/** This is the counterpart to activate() (see above). If there is
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* nothing for deactivate() to do then the plugin writer may provide
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* a NULL rather than an empty function.
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*
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* Hosts must deactivate all activated units after they have been run()
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* for the last time. This call SHOULD be made as close to the last
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* run() call as possible and indicates to real-time plugins that
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* they are no longer live, however plugins MUST NOT rely on prompt
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* deactivation. Note that connect_port() may be called before or
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* after a call to deactivate().
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*
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* Note that deactivation is not similar to pausing as the plugin
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* instance will be reinitialised when activate() is called to reuse it.
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* Hosts MUST NOT call deactivate() unless activate() was previously
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* called. */
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void (*deactivate)(LV2_Handle Instance);
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/** This is the counterpart to instantiate() (see above). Once an instance
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* of a plugin has been finished with it can be deleted using this
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* function. The instance handle passed ceases to be valid after
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* this call.
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*
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* If activate() was called for a plugin instance then a corresponding
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* call to deactivate() MUST be made before cleanup() is called.
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* Hosts MUST NOT call cleanup() unless instantiate() was previously
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* called. */
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void (*cleanup)(LV2_Handle Instance);
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} LV2_Descriptor;
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/* ****************************************************************** */
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/** Accessing a Plugin:
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*
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* The exact mechanism by which plugins are loaded is host-dependent,
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* however all most hosts will need to know is the URI of the plugin they
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* wish to load. The environment variable LV2_PATH, if present, should
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* contain a colon-separated path indicating directories (containing
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* plugin bundle subdirectories) that should be searched (in order)
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* for plugins. It is expected that hosts will use a library to provide
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* this functionality.
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*
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* A plugin programmer must include a function called "lv2_descriptor"
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* with the following function prototype within the shared object
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* file. This function will have C-style linkage (if you are using
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* C++ this is taken care of by the 'extern "C"' clause at the top of
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* the file).
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*
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* A host will find the plugin shared object file by one means or another,
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* find the lv2_descriptor() function, call it, and proceed from there.
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*
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* Plugin types are accessed by index (not ID) using values from 0
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* upwards. Out of range indexes must result in this function returning
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* NULL, so the plugin count can be determined by checking for the least
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* index that results in NULL being returned. Index has no meaning,
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* hosts MUST NOT depend on it remaining constant (ie when serialising)
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* in any way. */
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const LV2_Descriptor * lv2_descriptor(unsigned long Index);
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/** Datatype corresponding to the lv2_descriptor() function. */
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typedef const LV2_Descriptor *
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(*LV2_Descriptor_Function)(unsigned long Index);
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/* ******************************************************************** */
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#ifdef __cplusplus
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}
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#endif
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#endif /* LV2_INCLUDED */
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