From eb43c8896480114b224755e824fae2e2f7485256 Mon Sep 17 00:00:00 2001 From: David Robillard Date: Mon, 21 Nov 2011 01:36:00 +0000 Subject: Move ns to lv2/ns so repository top level can be used as an include dir directly. --- lv2/ns/ext/state/state.ttl | 231 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 231 insertions(+) create mode 100644 lv2/ns/ext/state/state.ttl (limited to 'lv2/ns/ext/state/state.ttl') diff --git a/lv2/ns/ext/state/state.ttl b/lv2/ns/ext/state/state.ttl new file mode 100644 index 0000000..c79188e --- /dev/null +++ b/lv2/ns/ext/state/state.ttl @@ -0,0 +1,231 @@ +# LV2 State Extension +# Copyright 2010-2011 David Robillard +# Copyright 2010 Leonard Ritter +# +# 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: . +@prefix doap: . +@prefix foaf: . +@prefix lv2: . +@prefix rdf: . +@prefix rdfs: . + + + a lv2:Specification ; + doap:name "LV2 State" ; + doap:shortdesc "An interface for LV2 plugins to save and restore state." ; + doap:license ; + doap:release [ + doap:revision "0.2" ; + doap:created "2011-11-14" + ] ; + doap:developer [ + a foaf:Person ; + foaf:name "Leonard Ritter" ; + foaf:homepage ; + ] ; + doap:maintainer [ + a foaf:Person ; + foaf:name "David Robillard" ; + foaf:homepage ; + rdfs:seeAlso + ] ; + lv2:documentation """ +

This extension provides a mechanism for plugins to save and restore state +across instances, allowing hosts to save, restore, clone, or take a snapshot of +a plugin instance's state at any point in time. The intention is for a plugin +instance's state to be completely described by port values (as with all +LV2 plugins) and a simple dictionary.

+ +

The state described by this extension is conceptually a single +key/value dictionary, where keys are URIDs and values are type-tagged blobs of +any type. The plugin provides an LV2_State_Interface for working with this +state. To save or restore, the host calls LV2_State_Interface::save() or +LV2_State_Interface::restore(), 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.

+ +

Because state is a simple dictionary, hosts and plugins can work with it +easily from many languages and protocols. Keys are URIDs for performance +reasons as well as RDF compatibility, which makes it simple to serialise state +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. +Specific keys may be described in Turtle on the fly or in extensions, +allowing plugins to use common well-defined keys.

+ +

This extension defines a conceptual model of state and a mechanism for +saving and restoring it, but no interface for manipulating it dynamically. +While no such mechanism is defined here, dynamic control of plugins SHOULD be +achieved by generic manipulations of the same conceptual state dictionary used +by this extension (e.g. plugin->set(key, value)). Accordingly, +plugins SHOULD use meaningful and well-defined keys wherever possible.

+ +

In pseudo code, a typical use case in a plugin is:

+
+#define NS_EG   "http://example.org/"
+#define NS_ATOM "http://lv2plug.in/ns/ext/atom#"
+
+LV2_Handle my_instantiate(...)
+{
+    MyPlugin* plugin = ...;
+    plugin->uris.atom_String = map_uri(NS_ATOM "String");
+    plugin->uris.eg_greeting = map_uri(NS_EG "greeting");
+    plugin->state.greeting   = strdup("Hello");
+    return plugin;
+}
+
+void my_save(LV2_Handle                 instance,
+             LV2_State_Store_Function   store,
+             void*                      handle,
+             uint32_t                   flags,
+             const LV2_Feature *const * features)
+
+{
+    MyPlugin*   plugin   = (MyPlugin*)instance;
+    const char* greeting = plugin->state.greeting;
+
+    store(handle,
+          plugin->uris.eg_greeting,
+          greeting,
+          strlen(greeting) + 1,
+          plugin->uris.atom_String,
+          LV2_STATE_IS_POD | LV2_STATE_IS_PORTABLE);
+}
+
+void my_restore(LV2_Handle                  instance,
+                LV2_State_Retrieve_Function retrieve,
+                void*                       handle,
+                uint32_t                    flags,
+                const LV2_Feature *const *   features)
+{
+    MyPlugin* plugin = (MyPlugin*)instance;
+
+    size_t      size;
+    uint32_t    type;
+    uint32_t    flags;
+    const char* greeting = retrieve(handle,
+                                    plugin->uris.eg_greeting,
+                                    &size,
+                                    &type,
+                                    &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, LV2_STATE_INTERFACE_URI)) {
+        return &state_iface;
+    }
+}
+
+ +

Similarly, a typical use case in a host is:

+
+int store_callback(void*       handle,
+                   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*)handle;
+        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, &state_map,
+               LV2_STATE_IS_POD|LV2_STATE_IS_NATIVE);
+    return state_map;
+}
+
+""" . + +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 +LV2_STATE_INTERFACE_URI.

+ +

The plugin data file should describe this like so:

+
+@prefix state: <http://lv2plug.in/ns/ext/state#> .
+
+<plugin>
+    a lv2:Plugin ;
+    lv2:extensionData state:Interface .
+
+""" . + +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.:

+
+@prefix eg: <http://example.org/> .
+
+<plugininstance> state:instanceState [
+    eg:somekey "some value" ;
+    eg:someotherkey "some other value" ;
+    eg:favourite-number 2
+] .
+
+

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.

+""" . -- cgit v1.2.1