Add state extension (a minor improvement to persist).

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.
+""" .