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authorDavid Robillard <d@drobilla.net>2015-02-18 16:45:27 -0500
committerDavid Robillard <d@drobilla.net>2015-02-18 16:45:27 -0500
commit9b4b2b68f50db95da7d63a62a8ebee90be58da58 (patch)
tree553a61146a9f66f39c68e74950565e531bd3862d /lv2/lv2plug.in/ns/lv2core/Plugin.hpp
parent3520e1fba6c5ab47b5f01c6f0755abe45d622a6d (diff)
downloadlv2-9b4b2b68f50db95da7d63a62a8ebee90be58da58.tar.xz
Add preliminary C++ work.
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+/*
+ Copyright 2015 David Robillard <http://drobilla.net>
+
+ Permission to use, copy, modify, and/or distribute this software for any
+ purpose with or without fee is hereby granted, provided that the above
+ copyright notice and this permission notice appear in all copies.
+
+ THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#ifndef LV2_PLUGIN_HPP
+#define LV2_PLUGIN_HPP
+
+#include "lv2/lv2plug.in/ns/lv2core/lv2.h"
+
+namespace lv2 {
+
+/**
+ C++ wrapper for an LV2 plugin.
+
+ This interface is a convenience for plugin authors only, and is not an ABI
+ used by hosts. Plugin authors should inherit from this interface, and use
+ the resulting class as the template parameter to lv2::set_descriptor() to
+ initialise a descriptor for the plugin.
+
+ This class is a stateless interface and imposes no restrictions or overhead
+ compared to a plugin implemented using the underlying C interface. Note
+ that this is not a virtual class, so calling methods from a Plugin* base
+ pointer will not work. Instead, anything that must dispatch on Plugin
+ methods takes a template parameter for static dispatch.
+*/
+class Plugin
+{
+public:
+ /**
+ 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 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 yield the 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 RDF data to
+ determine which features are required and do not attempt to 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.
+ */
+ Plugin(double sample_rate,
+ const char* bundle_path,
+ const LV2_Feature*const* features)
+ {}
+
+ /**
+ 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).
+
+ 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 lv2core.ttl for details.
+
+ 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 run() since the block
+ allocated may only just be large enough to contain the data, and is not
+ guaranteed to remain constant between run() calls.
+
+ 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 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 RDF data (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(uint32_t port, void* data_location) {}
+
+ /**
+ 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() {}
+
+ /**
+ Run 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
+ lv2core.ttl for details).
+
+ As a special case, when `sample_count` is 0, the plugin should update
+ any output ports that represent a single instant in time (e.g. control
+ ports, but not audio ports). This is particularly useful for latent
+ plugins, which should update their latency output port so hosts can
+ pre-roll plugins to compute latency. Plugins MUST NOT crash when
+ `sample_count` is 0.
+
+ @param sample_count The block size (in samples) for which the plugin
+ instance must run.
+ */
+ void run(uint32_t sample_count) {}
+
+ /**
+ 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() {}
+
+ /**
+ 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. This function MUST return NULL for any
+ unsupported URI. If a plugin does not support any extension data, this
+ field may be NULL.
+
+ The host is never responsible for freeing the returned value.
+ */
+ static const void* extension_data(const char* uri) { return NULL; }
+};
+
+template<typename Plugin>
+static LV2_Handle s_instantiate(const LV2_Descriptor* descriptor,
+ double sample_rate,
+ const char* bundle_path,
+ const LV2_Feature* const* features) {
+ Plugin* t = new Plugin(sample_rate, bundle_path, features);
+ if (!t) {
+ delete t;
+ return nullptr;
+ }
+
+ return reinterpret_cast<LV2_Handle>(t);
+}
+
+template<typename Plugin>
+static void s_connect_port(LV2_Handle instance, uint32_t port, void* buf)
+{
+ reinterpret_cast<Plugin*>(instance)->connect_port(port, buf);
+}
+
+template<typename Plugin>
+static void s_activate(LV2_Handle instance)
+{
+ reinterpret_cast<Plugin*>(instance)->activate();
+}
+
+template<typename Plugin>
+static void s_run(LV2_Handle instance, uint32_t sample_count)
+{
+ reinterpret_cast<Plugin*>(instance)->run(sample_count);
+}
+
+template<typename Plugin>
+static void s_deactivate(LV2_Handle instance)
+{
+ reinterpret_cast<Plugin*>(instance)->deactivate();
+}
+
+template<typename Plugin>
+static void s_cleanup(LV2_Handle instance)
+{
+ delete reinterpret_cast<Plugin*>(instance);
+}
+
+/**
+ Get an LV2_Descriptor for a plugin class.
+
+ @code
+ static const LV2_Descriptor a = lv2::descriptor<Amp>("http://example.org/amp");
+ @endcode
+*/
+template<typename Plugin>
+static LV2_Descriptor
+descriptor(const char* uri)
+{
+ const LV2_Descriptor desc = { uri,
+ &s_instantiate<Plugin>,
+ &s_connect_port<Plugin>,
+ &s_activate<Plugin>,
+ &s_run<Plugin>,
+ &s_deactivate<Plugin>,
+ &s_cleanup<Plugin>,
+ &Plugin::extension_data };
+ return desc;
+}
+
+} /* namespace lv2 */
+
+#endif /* LV2_PLUGIN_HPP */