From ed78bbe5ba12be1f9bcc736f14c51da6b4f639f3 Mon Sep 17 00:00:00 2001 From: David Robillard Date: Wed, 8 Feb 2012 04:56:24 +0000 Subject: Rearrange tree so top level can be used as an include path for standard style LV2 includes. --- lv2/lv2plug.in/ns/ext/state/state.ttl | 359 ++++++++++++++++++++++++++++++++++ 1 file changed, 359 insertions(+) create mode 100644 lv2/lv2plug.in/ns/ext/state/state.ttl (limited to 'lv2/lv2plug.in/ns/ext/state/state.ttl') diff --git a/lv2/lv2plug.in/ns/ext/state/state.ttl b/lv2/lv2plug.in/ns/ext/state/state.ttl new file mode 100644 index 0000000..6c0656a --- /dev/null +++ b/lv2/lv2plug.in/ns/ext/state/state.ttl @@ -0,0 +1,359 @@ +# LV2 State Extension +# Copyright 2010-2012 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 dcs: . +@prefix doap: . +@prefix foaf: . +@prefix lv2: . +@prefix rdf: . +@prefix rdfs: . +@prefix state: . + + + a foaf:Person ; + foaf:name "David Robillard" ; + foaf:homepage ; + foaf:mbox ; + rdfs:seeAlso . + + + 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 "0.5" ; + doap:created "2012-01-29" ; + dcs:blame + ] ; + 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 simple mechanism for plugins to save and restore +state across instances, allowing hosts to save and restore a plugin instance's +state at any time. The goal is for an instance's state to be +completely described by port values (as with all LV2 plugins) and a +dictionary.

+ +

The state described by this extension is conceptually a simple +key:value dictionary, where keys are URIDs (URIs mapped to integers) and values +are type-tagged blobs of any type. A single key:value pair is called a +property. To implement state, the plugin provides a state:Interface to +the host. 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 property. The host is free to implement property storage and retrieval +in any way.

+ +

This state model is simple yet has many benefits:

+
    +
  • URID keys provide both fast performance and RDF compatibility.
    • +
  • Fully extensible, no limitations on keys or value types.
    • +
  • Easy to serialise in many formats (e.g. any RDF syntax, plain + text, JSON, XML, key:value databases, SQL, s-expressions, etc.).
    • +
  • Elegantly described in Turtle, which is useful for describing presets + or default state in LV2 data files (the predicate state:state is provided + for this purpose).
    • +
  • Does not impose any file formats, data structures, or file system + requirements.
    • +
  • Suitable for portable persistent state as well as fast in-memory + snapshots.
    • +
  • Easily stored in a typical map or dictionary data + structure.
    • +
  • Keys may be defined by extensions and used by several plugins, + making state meaningful enabling dynamic state control.
    • +
+ +

Implementations or further extensions which work with plugin state +(including dynamic plugin control) SHOULD work entirely within this model. +That is, do not complicate the state model. All +information required to express an instance's state at any given time can, and +should, be expressed within this model.

+ +

Plugin Code Example

+ +
+#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;
+    }
+}
+
+ +

Host Code Example

+ +
+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;
+}
+
+ +

Referring to Existing Files

+ +

Plugins may need to refer to files (e.g. loaded samples) in their state. +This is done by storing the file's path as a property just like any other +value. However, there are some rules which MUST be followed when storing +paths, see state:mapPath for details.

+ +

Creating New Files or Directories

+ +

Implementations are strongly encouraged to avoid the use of files and simply +store all state as properties whenever possible. However, occasionally the +ability to create files is necessary. The feature state:newPath makes this possible, if it is provided by the +host.

+""" . + +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:State + a rdfs:Class ; + rdfs:label "Plugin Instance State" ; + lv2:documentation """ +

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:State as the subject (see state:state 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:state + a rdf:Property ; + rdfs:range state:State ; + lv2:documentation """ +

Predicate to relate a plugin instance to its State. 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:state [
+        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 this extension.

+""" . + +state:mapPath + a lv2:Feature ; + rdfs:label "Support for storing paths in files" ; + lv2:documentation """ + +

This feature maps absolute paths to/from abstract paths which are +stored in state. To support this feature a host must pass an LV2_Feature with +URI LV2_STATE_MAP_PATH_URI and data pointed to an LV2_State_Map_Path to the +plugin's LV2_State_Interface methods.

+ +

The plugin MUST map all paths stored in its state (including in any +files in its state). This is necessary to enable host to handle file system +references correctly, e.g. for distribution or archival.

+ +

For example, a plugin may write a path to a state file like so:

+ +
+void write_path(LV2_State_Map_Path* map_path, FILE* myfile, const char* path)
+{
+    char* abstract_path = map_path->abstract_path(map_path->handle, path);
+    fprintf(myfile, "%s", abstract_path);
+    free(abstract_path);
+}
+
+ +

Then, later reload the path like so:

+ +
+char* read_path(LV2_State_Map_Path* map_path, FILE* myfile)
+{
+    /* Obviously this is not production quality code! */
+    char abstract_path[1024];
+    fscanf(myfile, "%s", abstract_path);
+    return map_path->absolute_path(map_path->handle, abstract_path);
+}
+
+""" . + +state:makePath + a lv2:Feature ; + rdfs:label "Support for creating new files and directories" ; + lv2:documentation """ + +

This feature allows plugins to create new files and/or directories. To +support this feature the host passes an LV2_Feature with URI +LV2_STATE_MAKE_PATH_URI and data pointed to an LV2_State_Make_Path to the +plugin. The host may make this feature available only during save by passing +it to LV2_State_Interface::save(), or available any time by passing it to +LV2_Descriptor::instantiate(). If passed to LV2_State_Interface::save(), the +feature MUST NOT be used beyond the scope of that call.

+ +

The plugin is guaranteed a hierarchial namespace unique to that plugin +instance, and may expect the returned path to have the requested path as a +suffix. There is one such namespace, even if the feature is passed to +both LV2_Descriptor::instantiate() and +LV2_State_Interface::save(). Beyond this, the plugin MUST NOT make any +assumptions about the returned paths.

+ +

Like any other paths, the plugin MUST map these paths using state:mapPath before storing them in state. The plugin +MUST NOT assume these paths will be available across a save/restore otherwise, +i.e. only mapped paths saved to state are persistent, any other created paths +are temporary.

+ +

For example, a plugin may create a file in a subdirectory like so:

+ +
+char* save_myfile(LV2_State_Make_Path* make_path)
+{
+    char* path   = make_path->path(make_path->handle, "foo/bar/myfile.txt");
+    FILE* myfile = fopen(path, 'w');
+    fprintf(myfile, "Hello");
+    fclose(myfile);
+    return path;
+}
+
+""" . + +state:Path + a rdfs:Class ; + rdfs:label "Path" ; + lv2:documentation """ +

A path to a file or directory.

+ +

The format of a state:Path is a C string, possibly escaped or otherwise +restricted in a system-specific manner. This URI (LV2_STATE_PATH_URI), mapped +to an integer, MUST be used as the type parameter for any files +passed to the LV2_State_Store_Function; and will likewise be returned by the +corresponding call to the LV2_State_Retrieve_Function.

+ +

When storing and retrieving a path, the plugin MUST NOT assume the same path +will be restored. However, the restored path will refer to a file with +equivalent contents to the original.

+""" . -- cgit v1.2.1