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authorDavid Robillard <d@drobilla.net>2011-11-04 00:54:20 +0000
committerDavid Robillard <d@drobilla.net>2011-11-04 00:54:20 +0000
commit6d6e2458c3dff83ee6f68a1c7c5f7ed69bb121ab (patch)
tree16478673f3f633a1fc88ce4d09f3ed4c0c6c36b5 /ext/state.lv2
parent1c80ffdd50c201e15a913759e3acb58ff08be5b8 (diff)
downloadlv2-6d6e2458c3dff83ee6f68a1c7c5f7ed69bb121ab.tar.xz
Add state extension (a minor improvement to persist).
Diffstat (limited to 'ext/state.lv2')
-rw-r--r--ext/state.lv2/manifest.ttl9
-rw-r--r--ext/state.lv2/state.h248
-rw-r--r--ext/state.lv2/state.ttl230
3 files changed, 487 insertions, 0 deletions
diff --git a/ext/state.lv2/manifest.ttl b/ext/state.lv2/manifest.ttl
new file mode 100644
index 0000000..ce76fd9
--- /dev/null
+++ b/ext/state.lv2/manifest.ttl
@@ -0,0 +1,9 @@
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+
+<http://lv2plug.in/ns/ext/state>
+ a lv2:Specification ;
+ lv2:minorVersion 0 ;
+ lv2:microVersion 1 ;
+ rdfs:seeAlso <state.ttl> .
+
diff --git a/ext/state.lv2/state.h b/ext/state.lv2/state.h
new file mode 100644
index 0000000..56ebfda
--- /dev/null
+++ b/ext/state.lv2/state.h
@@ -0,0 +1,248 @@
+/*
+ Copyright 2010-2011 David Robillard <http://drobilla.net>
+ Copyright 2010 Leonard Ritter <paniq@paniq.org>
+
+ 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.
+*/
+
+/**
+ @file
+ C API for the LV2 State extension <http://lv2plug.in/ns/ext/state>.
+*/
+
+#ifndef LV2_STATE_H
+#define LV2_STATE_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "lv2/lv2plug.in/ns/lv2core/lv2.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state"
+
+/**
+ Flags describing value characteristics.
+
+ These flags are used along with the value's type URI to determine how to
+ (de-)serialise the value data, or whether it is even possible to do so.
+*/
+typedef enum {
+
+ /**
+ Plain Old Data.
+
+ Values with this flag contain no references to non-stateent or
+ non-global resources (e.g. pointers, handles, local paths, etc.). It is
+ safe to copy POD values with a simple memcpy and store them for use at
+ any time in the future on a machine with a compatible architecture
+ (e.g. the same endianness and alignment).
+
+ Implementations MUST NOT attempt to copy or serialise a non-POD value if
+ they do not understand its type (and thus know how to correctly do so).
+ */
+ LV2_STATE_IS_POD = 1,
+
+ /**
+ Portable (architecture independent) data.
+
+ Values with this flag are in a format that is usable on any
+ architecture, i.e. if the value is saved on one machine it can safely be
+ restored on another machine regardless of endianness, alignment, etc.
+ */
+ LV2_STATE_IS_PORTABLE = 1 << 1,
+
+ /**
+ Native data.
+
+ This flag is used by the host to indicate that the saved data is only
+ going to be used locally in the currently running process (e.g. for
+ instance duplication or snapshots), so the plugin should use the most
+ efficient representation possible and not worry about serialisation
+ and portability.
+ */
+ LV2_STATE_IS_NATIVE = 1 << 2
+
+} LV2_State_Flags;
+
+/**
+ A host-provided function to store a property.
+ @param callback_data Must be the callback_data passed to LV2_State_Interface.save().
+ @param key The key (predicate) to store @c value under (URI mapped integer).
+ @param value Pointer to the value (object) to be stored.
+ @param size The size of the data at @c value in bytes.
+ @param type The type of @c value (URI).
+ @param flags LV2_State_Flags for @c value.
+ @return 0 on success, otherwise a non-zero error code.
+
+ The host passes a callback of this type to LV2_State_Interface.save(). This callback
+ is called repeatedly by the plugin within LV2_State_Interface.save() to store all
+ the statements that describe its current state.
+
+ The host MAY fail to store a property if the type is not understood and is
+ not LV2_STATE_IS_POD and/or LV2_STATE_IS_PORTABLE. Implementations are
+ encouraged to use POD and portable values (e.g. string literals) wherever
+ possible, and use common types (e.g. types from
+ http://lv2plug.in/ns/ext/atom) regardless, since hosts are likely to already
+ contain the necessary implementation.
+
+ Note that @c size MUST be > 0, and @c value MUST point to a valid region of
+ memory @c size bytes long (this is required to make restore unambiguous).
+
+ The plugin MUST NOT attempt to use this function outside of the
+ LV2_State_Interface.restore() context.
+*/
+typedef int (*LV2_State_Store_Function)(
+ void* callback_data,
+ uint32_t key,
+ const void* value,
+ size_t size,
+ uint32_t type,
+ uint32_t flags);
+
+/**
+ A host-provided function to retrieve a property.
+ @param callback_data Must be the callback_data passed to
+ LV2_State_Interface.restore().
+ @param key The key (predicate) of the property to retrieve (URI).
+ @param size (Output) If non-NULL, set to the size of the restored value.
+ @param type (Output) If non-NULL, set to the type of the restored value.
+ @param flags (Output) If non-NULL, set to the LV2_State_Flags for
+ the returned value.
+ @return A pointer to the restored value (object), or NULL if no value
+ has been stored under @c key.
+
+ A callback of this type is passed by the host to
+ LV2_State_Interface.restore(). This callback is called repeatedly by the
+ plugin within LV2_State_Interface.restore() to retrieve any properties it
+ requires to restore its state.
+
+ The returned value MUST remain valid until LV2_State_Interface.restore() returns.
+
+ The plugin MUST NOT attempt to use this function, or any value returned from
+ it, outside of the LV2_State_Interface.restore() context. Returned values MAY be
+ copied for later use if necessary, assuming the plugin knows how to do so
+ correctly (e.g. the value is POD, or the plugin understands the type).
+*/
+typedef const void* (*LV2_State_Retrieve_Function)(
+ void* callback_data,
+ uint32_t key,
+ size_t* size,
+ uint32_t* type,
+ uint32_t* flags);
+
+/**
+ State Extension Data.
+
+ When the plugin's extension_data is called with argument LV2_STATE_URI,
+ the plugin MUST return an LV2_State structure, which remains valid for the
+ lifetime of the plugin.
+
+ The host can use the contained function pointers to save and restore the
+ state of a plugin instance at any time (provided the threading restrictions
+ for the given function are met).
+
+ The typical use case is to save the plugin's state when a project is saved,
+ and to restore the state when a project has been loaded. Other uses are
+ possible (e.g. cloning plugin instances or taking a snapshot of plugin
+ state).
+
+ Stored data is only guaranteed to be compatible between instances of plugins
+ with the same URI (i.e. if a change to a plugin would cause a fatal error
+ when restoring state saved by a previous version of that plugin, the plugin
+ URI MUST change just as it must when ports change incompatibly). Plugin
+ authors should consider this possibility, and always store sensible data
+ with meaningful types to avoid such compatibility issues in the future.
+*/
+typedef struct _LV2_State_Interface {
+
+ /**
+ Save plugin state using a host-provided @c store callback.
+
+ @param instance The instance handle of the plugin.
+ @param store The host-provided store callback.
+ @param callback_data An opaque pointer to host data, e.g. the map or
+ file where the values are to be stored. If @c store is called, this MUST
+ be passed as its callback_data parameter.
+ @param flags Flags describing desires properties of this save. The
+ plugin SHOULD use these values to determine the most appropriate and/or
+ efficient serialisation, but is not required to do so.
+
+ The plugin is expected to store everything necessary to completely
+ restore its state later (possibly much later, in a different process, on
+ a completely different machine, etc.)
+
+ The @c callback_data pointer and @c store function MUST NOT be used
+ beyond the scope of save().
+
+ This function has its own special threading class: it may not be called
+ concurrently with any "Instantiation" function, but it may be called
+ concurrently with functions in any other class, unless the definition of
+ that class prohibits it (e.g. it may not be called concurrently with a
+ "Discovery" function, but it may be called concurrently with an "Audio"
+ function. The plugin is responsible for any locking or lock-free
+ techniques necessary to make this possible.
+
+ Note that in the simple case where state is only modified by restore(),
+ there are no synchronization issues since save() is never called
+ concurrently with restore() (though run() may read it during a save).
+
+ Plugins that dynamically modify state while running, however, must take
+ care to do so in such a way that a concurrent call to save() will save a
+ consistent representation of plugin state for a single instant in time.
+ */
+ void (*save)(LV2_Handle instance,
+ LV2_State_Store_Function store,
+ void* callback_data,
+ uint32_t flags);
+
+ /**
+ Restore plugin state using a host-provided @c retrieve callback.
+
+ @param instance The instance handle of the plugin.
+ @param retrieve The host-provided retrieve callback.
+ @param callback_data An opaque pointer to host data, e.g. the map or
+ file from which the values are to be restored. If @c retrieve is
+ called, this MUST be passed as its callback_data parameter.
+ @param flags Currently unused.
+
+ The plugin MAY assume a restored value was set by a previous call to
+ LV2_State_Interface.save() by a plugin with the same URI.
+
+ The plugin MUST gracefully fall back to a default value when a value can
+ not be retrieved. This allows the host to reset the plugin state with an
+ empty map.
+
+ The @c callback_data pointer and @c store function MUST NOT be used
+ beyond the scope of restore().
+
+ This function is in the "Instantiation" threading class as defined by
+ LV2. This means it MUST NOT be called concurrently with any other
+ function on the same plugin instance.
+ */
+ void (*restore)(LV2_Handle instance,
+ LV2_State_Retrieve_Function retrieve,
+ void* callback_data,
+ uint32_t flags);
+
+} LV2_State_Interface;
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* LV2_STATE_H */
diff --git a/ext/state.lv2/state.ttl b/ext/state.lv2/state.ttl
new file mode 100644
index 0000000..70b0b5d
--- /dev/null
+++ b/ext/state.lv2/state.ttl
@@ -0,0 +1,230 @@
+# LV2 State Extension
+# Copyright 2010-2011 David Robillard <d@drobilla.net>
+# Copyright 2010 Leonard Ritter <paniq@paniq.org>
+#
+# 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.
+
+@prefix state: <http://lv2plug.in/ns/ext/state#> .
+@prefix doap: <http://usefulinc.com/ns/doap#> .
+@prefix foaf: <http://xmlns.com/foaf/0.1/> .
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
+@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
+
+<http://lv2plug.in/ns/ext/state>
+ a lv2:Specification ;
+ doap:name "LV2 State" ;
+ doap:license <http://opensource.org/licenses/isc-license> ;
+ doap:release [
+ doap:revision "0.1" ;
+ doap:created "2011-11-12"
+ ] ;
+ doap:developer [
+ a foaf:Person ;
+ foaf:name "Leonard Ritter" ;
+ foaf:homepage <http://paniq.org> ;
+ ] ;
+ doap:maintainer [
+ a foaf:Person ;
+ foaf:name "David Robillard" ;
+ foaf:homepage <http://drobilla.net/> ;
+ rdfs:seeAlso <http://drobilla.net/drobilla.rdf>
+ ] ;
+ lv2:documentation """
+<p>This extension provides a mechanism for plugins to save and restore state
+across instances, allowing hosts to save configuration/state/data with a
+project or fully clone (i.e. make a deep copy of) a plugin instance.</p>
+
+<p>This extension allows plugins to save private state data, i.e. data that is
+not contained in input ports. The motivating ideal is for the state of a
+plugin instance to be <em>entirely</em> described by port values (as with all
+LV2 plugins) and a key/value dictionary as defined by this extension. This
+mechanism is simple, yet sufficiently powerful to describe very advanced and
+complex state.</p>
+
+<p>The <q>state</q> described by this extension is conceptually a single
+key/value dictionary. Keys are URIs, and values are type-tagged blobs of any
+type. The plugin provides a save and restore method for saving and restoring
+state. To initiate a save or restore, the host calls these methods, passing a
+callback to be used for handling a single key/value pair. The host is free to
+implement saving and restoring in any way; the actual mechanism is completely
+abstract from the plugin's perspective.</p>
+
+<p>Because the state is a simple dictionary, hosts and plugins can work with
+state easily from many languages and protocols. Additionally, this format is
+simple and terse to serialise in many formats (e.g. any RDF syntax, JSON, XML,
+key/value databases such as BDB, etc.). In particular, state can be elegantly
+described in a plugin's Turtle description, which is useful for e.g. presets or
+default state.</p>
+
+<p>This extension defines a conceptual model of state and a mechanism for
+saving and restoring it, but no interface for manipulating that state
+dynamically. It is intended that a generic way to modify this state (e.g.
+with messages sent via ports) is the preferred way to achieve more advanced
+plugin control than control ports provide, but the details of this mechanism
+should be addressed by a separate extension.</p>
+
+<p>In pseudo code, a typical use case in a plugin is:</p>
+<pre class="c-code">
+#define NS_EG "http://example.org/"
+#define NS_ATOM "http://lv2plug.in/ns/ext/atom#"
+
+LV2_Handle my_instantiate(...)
+{
+ MyPlugin* plugin = ...;
+ LV2_URI_Map_Feature* map = ...;
+ plugin->uri_greeting_key = map->uri_to_id(..., NULL, NS_EG "greeting");
+ plugin->uri_xsd_string = map->uri_to_id(..., NULL, NS_ATOM "String");
+ plugin->state->greeting = strdup("Hello");
+ return plugin;
+}
+
+void my_save(LV2_Handle instance,
+ LV2_State_Store_Function store,
+ void* callback_data,
+ uint32_t flags)
+{
+ MyPlugin* plugin = (MyPlugin*)instance;
+ const char* greeting = plugin->state->greeting;
+
+ store(callback_data,
+ plugin->uri_greeting_key,
+ greeting,
+ strlen(greeting) + 1,
+ plugin->uri_xsd_string,
+ LV2_STATE_IS_POD | LV2_STATE_IS_PORTABLE);
+}
+
+void my_restore(LV2_Handle instance,
+ LV2_State_Retrieve_Function retrieve,
+ void* callback_data,
+ uint32_t flags)
+{
+ MyPlugin* plugin = (MyPlugin*)instance;
+
+ size_t size;
+ uint32_t type;
+ uint32_t flags;
+ const char* greeting = retrieve(callback_data,
+ plugin->uri_greeting_key,
+ &amp;size,
+ &amp;type,
+ &amp;flags);
+
+ if (greeting) {
+ free(plugin->state->greeting);
+ plugin->state->greeting = strdup(greeting);
+ } else {
+ plugin->state->greeting = strdup("Hello");
+ }
+}
+
+const void* my_extension_data(const char* uri)
+{
+ static const LV2_State_Interface state_iface = { my_save, my_restore };
+ if (!strcmp(uri, "http://lv2plug.in/ns/ext/state#Interface")) {
+ return &state_iface;
+ }
+}
+</pre>
+
+<p>Similarly, a typical use case in a host is:</p>
+<pre class="c-code">
+int store_callback(void* callback_data,
+ uint32_t key,
+ const void* value,
+ size_t size,
+ uint32_t type,
+ uint32_t flags)
+{
+ if ((flags & LV2_STATE_IS_POD)) {
+ /* We only care about POD since we're keeping state in memory only.
+ If this was for disk or network storage/transmission,
+ LV2_STATE_IS_PORTABLE would have to be checked as well.
+ */
+ Map* state_map = (Map*)callback_data;
+ state_map->insert(key, Value(copy(value), size, type, pod));
+ return 0;
+ } else {
+ return 1; /* Non-POD events are unsupported. */
+ }
+}
+
+Map get_plugin_state(LV2_Handle instance)
+{
+ LV2_State* state = instance.extension_data("http://lv2plug.in/ns/ext/state");
+ Map state_map;
+ /** Request a fast/native/POD save, since we're just copying in memory */
+ state.save(instance, store_callback, &amp;state_map,
+ LV2_STATE_IS_POD|LV2_STATE_IS_NATIVE);
+ return state_map;
+}
+</pre>
+""" .
+
+state:Interface
+ a rdfs:Class ;
+ rdfs:subClassOf lv2:ExtensionData ;
+ lv2:documentation """
+A structure (LV2_State_Interface) which contains functions to be called by the
+host to save and restore state. In order to support this extension, the plugin
+must return a valid LV2_State_Interface from LV2_Descriptor::extension_data()
+when it is called with URI "http://lv2plug.in/ns/ext/state#StateInterface".
+
+The plugin data file should describe this like so:
+<pre class="turtle-code">
+@prefix state: &lt;http://lv2plug.in/ns/ext/state#&gt; .
+
+&lt;plugin&gt;
+ a lv2:Plugin ;
+ lv2:extensionData state:Interface .
+</pre>
+""" .
+
+state:InstanceState
+ a rdfs:Class ;
+ rdfs:label "Plugin Instance State" ;
+ rdfs:comment """
+This class is used to express a plugin instance's state in RDF. The key/value
+properties of the instance form the predicate/object (respectively) of triples
+with a state:InstanceState as the subject (see state:instanceState for an
+example). This may be used wherever it is useful to express a plugin instance's
+state in RDF (e.g. for serialisation, storing in a model, or transmitting over
+a network). Note that this class is provided because it may be useful for
+hosts, plugins, or extensions that work with instance state, but its use is not
+required to support the LV2 State extension.
+""" .
+
+state:instanceState
+ a rdf:Property ;
+ rdfs:range state:InstanceState ;
+ lv2:documentation """
+Predicate to relate a plugin instance to an InstanceState. This may be used
+wherever the state of a particular plugin instance needs to be represented.
+Note that the domain of this property is unspecified, since LV2 does not define
+any RDF class for plugin instance. This predicate may be used wherever it makes
+sense to do so, e.g.:
+<pre class="turtle-code">
+@prefix eg: &lt;http://example.org/&gt; .
+
+&lt;plugininstance&gt; state:instanceState [
+ eg:somekey "some value" ;
+ eg:someotherkey "some other value" ;
+ eg:favourite-number 2
+] .
+</pre>
+Note that this property is provided because it may be useful for hosts,
+plugins, or extensions that work with instance state, but its use is not
+required to support the LV2 State extension.
+""" .