Install standard headers to simpler include paths

4 files changed, 819 insertions, 0 deletions

diff --git a/lv2/state/lv2-state.doap.ttl b/lv2/state/lv2-state.doap.ttl
new file mode 100644
index 0000000..fd87a13
--- /dev/null
+++ b/lv2/state/lv2-state.doap.ttl
@@ -0,0 +1,66 @@
+@prefix dcs: <http://ontologi.es/doap-changeset#> .
+@prefix doap: <http://usefulinc.com/ns/doap#> .
+@prefix foaf: <http://xmlns.com/foaf/0.1/> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+
+<http://lv2plug.in/ns/ext/state>
+	a doap:Project ;
+	doap:created "2010-11-09" ;
+	doap:name "LV2 State" ;
+	doap:shortdesc "An interface for LV2 plugins to save and restore state." ;
+	doap:license <http://opensource.org/licenses/isc> ;
+	doap:developer <http://lv2plug.in/ns/meta#paniq> ,
+		<http://drobilla.net/drobilla#me> ;
+	doap:maintainer <http://drobilla.net/drobilla#me> ;
+	doap:release [
+		doap:revision "2.3" ;
+		doap:created "2016-10-19" ;
+		dcs:blame <http://drobilla.net/drobilla#me> ;
+		dcs:changeset [
+			dcs:item [
+				rdfs:label "Add state:StateChanged for notification events."
+			]
+		]
+	] , [
+		doap:revision "2.2" ;
+		doap:created "2016-07-31" ;
+		doap:file-release <http://lv2plug.in/spec/lv2-1.14.0.tar.bz2> ;
+		dcs:blame <http://drobilla.net/drobilla#me> ;
+		dcs:changeset [
+			dcs:item [
+				rdfs:label "Add LV2_STATE_ERR_NO_SPACE status flag."
+			] , [
+				rdfs:label "Add state:threadSafeRestore feature for dropout-free state restoration."
+			]
+		]
+	] , [
+		doap:revision "2.0" ;
+		doap:created "2013-01-16" ;
+		doap:file-release <http://lv2plug.in/spec/lv2-1.4.0.tar.bz2> ;
+		dcs:blame <http://drobilla.net/drobilla#me> ;
+		dcs:changeset [
+			dcs:item [
+				rdfs:label "Add state:loadDefaultState feature so plugins can have their default state loaded without hard-coding default state as a special case."
+			]
+		]
+	] , [
+		doap:revision "1.2" ;
+		doap:created "2012-10-14" ;
+		doap:file-release <http://lv2plug.in/spec/lv2-1.2.0.tar.bz2> ;
+		dcs:blame <http://drobilla.net/drobilla#me> ;
+		dcs:changeset [
+			dcs:item [
+				rdfs:label "Use consistent label style."
+			]
+		]
+	] , [
+		doap:revision "1.0" ;
+		doap:created "2012-04-17" ;
+		doap:file-release <http://lv2plug.in/spec/lv2-1.0.0.tar.bz2> ;
+		dcs:blame <http://drobilla.net/drobilla#me> ;
+		dcs:changeset [
+			dcs:item [
+				rdfs:label "Initial release."
+			]
+		]
+	] .
diff --git a/lv2/state/manifest.ttl b/lv2/state/manifest.ttl
new file mode 100644
index 0000000..2a54874
--- /dev/null
+++ b/lv2/state/manifest.ttl
@@ -0,0 +1,8 @@
+@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 2 ;
+	lv2:microVersion 3 ;
+	rdfs:seeAlso <state.ttl> .
diff --git a/lv2/state/state.h b/lv2/state/state.h
new file mode 100644
index 0000000..ffc40d1
--- /dev/null
+++ b/lv2/state/state.h
@@ -0,0 +1,363 @@
+/*
+  Copyright 2010-2016 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.
+*/
+
+/**
+   @defgroup state State
+
+   An interface for LV2 plugins to save and restore state, see
+   <http://lv2plug.in/ns/ext/state> for details.
+
+   @{
+*/
+
+#ifndef LV2_STATE_H
+#define LV2_STATE_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "lv2/core/lv2.h"
+
+#define LV2_STATE_URI    "http://lv2plug.in/ns/ext/state"  ///< http://lv2plug.in/ns/ext/state
+#define LV2_STATE_PREFIX LV2_STATE_URI "#"                 ///< http://lv2plug.in/ns/ext/state#
+
+#define LV2_STATE__State             LV2_STATE_PREFIX "State"              ///< http://lv2plug.in/ns/ext/state#State
+#define LV2_STATE__interface         LV2_STATE_PREFIX "interface"          ///< http://lv2plug.in/ns/ext/state#interface
+#define LV2_STATE__loadDefaultState  LV2_STATE_PREFIX "loadDefaultState"   ///< http://lv2plug.in/ns/ext/state#loadDefaultState
+#define LV2_STATE__makePath          LV2_STATE_PREFIX "makePath"           ///< http://lv2plug.in/ns/ext/state#makePath
+#define LV2_STATE__mapPath           LV2_STATE_PREFIX "mapPath"            ///< http://lv2plug.in/ns/ext/state#mapPath
+#define LV2_STATE__state             LV2_STATE_PREFIX "state"              ///< http://lv2plug.in/ns/ext/state#state
+#define LV2_STATE__threadSafeRestore LV2_STATE_PREFIX "threadSafeRestore"  ///< http://lv2plug.in/ns/ext/state#threadSafeRestore
+#define LV2_STATE__StateChanged      LV2_STATE_PREFIX "StateChanged"       ///< http://lv2plug.in/ns/ext/state#StateChanged
+
+#ifdef __cplusplus
+extern "C" {
+#else
+#    include <stdbool.h>
+#endif
+
+typedef void* LV2_State_Handle;            ///< Opaque handle for state save/restore
+typedef void* LV2_State_Map_Path_Handle;   ///< Opaque handle for state:mapPath feature
+typedef void* LV2_State_Make_Path_Handle;  ///< Opaque handle for state:makePath feature
+
+/**
+   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 pointers or references to other areas
+	   of memory.  It is safe to copy POD values with a simple memcpy and store
+	   them for the duration of the process.  A POD value is not necessarily
+	   safe to trasmit between processes or machines (e.g. filenames are POD),
+	   see LV2_STATE_IS_PORTABLE for details.
+
+	   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.  A portable value saved on one machine can be restored on
+	   another machine regardless of architecture.  The format of portable
+	   values MUST NOT depend on architecture-specific properties like
+	   endianness or alignment.  Portable values MUST NOT contain filenames.
+	*/
+	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 status code for state functions. */
+typedef enum {
+	LV2_STATE_SUCCESS         = 0,  /**< Completed successfully. */
+	LV2_STATE_ERR_UNKNOWN     = 1,  /**< Unknown error. */
+	LV2_STATE_ERR_BAD_TYPE    = 2,  /**< Failed due to unsupported type. */
+	LV2_STATE_ERR_BAD_FLAGS   = 3,  /**< Failed due to unsupported flags. */
+	LV2_STATE_ERR_NO_FEATURE  = 4,  /**< Failed due to missing features. */
+	LV2_STATE_ERR_NO_PROPERTY = 5,  /**< Failed due to missing property. */
+	LV2_STATE_ERR_NO_SPACE    = 6   /**< Failed due to insufficient space. */
+} LV2_State_Status;
+
+/**
+   A host-provided function to store a property.
+   @param handle Must be the handle passed to LV2_State_Interface.save().
+   @param key The key to store `value` under (URID).
+   @param value Pointer to the value to be stored.
+   @param size The size of `value` in bytes.
+   @param type The type of `value` (URID).
+   @param flags LV2_State_Flags for `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 to store all the properties that
+   describe its current state.
+
+   DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY.  Best is to use keys from
+   existing vocabularies.  If nothing appropriate is available, use http URIs
+   that point to somewhere you can host documents so documentation can be made
+   resolvable (e.g. a child of the plugin or project URI).  If this is not
+   possible, invent a URN scheme, e.g. urn:myproj:whatever.  The plugin MUST
+   NOT pass an invalid URI key.
+
+   The host MAY fail to store a property for whatever reason, but SHOULD
+   store any property that is LV2_STATE_IS_POD and LV2_STATE_IS_PORTABLE.
+   Implementations SHOULD use the types from the LV2 Atom extension
+   (http://lv2plug.in/ns/ext/atom) wherever possible.  The plugin SHOULD
+   attempt to fall-back and avoid the error if possible.
+
+   Note that `size` MUST be > 0, and `value` MUST point to a valid region of
+   memory `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 LV2_State_Status (*LV2_State_Store_Function)(
+	LV2_State_Handle handle,
+	uint32_t         key,
+	const void*      value,
+	size_t           size,
+	uint32_t         type,
+	uint32_t         flags);
+
+/**
+   A host-provided function to retrieve a property.
+   @param handle Must be the handle passed to LV2_State_Interface.restore().
+   @param key The key of the property to retrieve (URID).
+   @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 flags for the restored value.
+   @return A pointer to the restored value (object), or NULL if no value
+   has been stored under `key`.
+
+   A callback of this type is passed by the host to
+   LV2_State_Interface.restore().  This callback is called repeatedly by the
+   plugin 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.
+*/
+typedef const void* (*LV2_State_Retrieve_Function)(
+	LV2_State_Handle handle,
+	uint32_t         key,
+	size_t*          size,
+	uint32_t*        type,
+	uint32_t*        flags);
+
+/**
+   LV2 Plugin State Interface.
+
+   When the plugin's extension_data is called with argument
+   LV2_STATE__interface, the plugin MUST return an LV2_State_Interface
+   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
+   of the functions are met.
+
+   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 problems in the future.
+*/
+typedef struct _LV2_State_Interface {
+	/**
+	   Save plugin state using a host-provided `store` callback.
+
+	   @param instance The instance handle of the plugin.
+	   @param store The host-provided store callback.
+	   @param handle An opaque pointer to host data which MUST be passed as the
+	   handle parameter to `store` if it is called.
+	   @param flags Flags describing desired properties of this save.  These
+	   flags may be used to determine the most appropriate values to store.
+	   @param features Extensible parameter for passing any additional
+	   features to be used for this save.
+
+	   The plugin is expected to store everything necessary to completely
+	   restore its state later.  Plugins SHOULD store simple POD data whenever
+	   possible, and consider the possibility of state being restored much
+	   later on a different machine.
+
+	   The `handle` pointer and `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.
+	*/
+	LV2_State_Status (*save)(LV2_Handle                 instance,
+	                         LV2_State_Store_Function   store,
+	                         LV2_State_Handle           handle,
+	                         uint32_t                   flags,
+	                         const LV2_Feature *const * features);
+
+	/**
+	   Restore plugin state using a host-provided `retrieve` callback.
+
+	   @param instance The instance handle of the plugin.
+	   @param retrieve The host-provided retrieve callback.
+	   @param handle An opaque pointer to host data which MUST be passed as the
+	   handle parameter to `retrieve` if it is called.
+	   @param flags Currently unused.
+	   @param features Extensible parameter for passing any additional
+	   features to be used for this restore.
+
+	   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 `handle` pointer and `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.
+	*/
+	LV2_State_Status (*restore)(LV2_Handle                  instance,
+	                            LV2_State_Retrieve_Function retrieve,
+	                            LV2_State_Handle            handle,
+	                            uint32_t                    flags,
+	                            const LV2_Feature *const *  features);
+} LV2_State_Interface;
+
+/**
+   Feature data for state:mapPath (@ref LV2_STATE__mapPath).
+*/
+typedef struct {
+	/**
+	   Opaque host data.
+	*/
+	LV2_State_Map_Path_Handle handle;
+
+	/**
+	   Map an absolute path to an abstract path for use in plugin state.
+	   @param handle MUST be the `handle` member of this struct.
+	   @param absolute_path The absolute path of a file.
+	   @return An abstract path suitable for use in plugin state.
+
+	   The plugin MUST use this function to map any paths that will be stored
+	   in plugin state.  The returned value is an abstract path which MAY not
+	   be an actual file system path; absolute_path() MUST be used to map
+	   it to an actual path in order to use the file.
+
+	   Plugins MUST NOT make any assumptions about abstract paths except that
+	   they can be mapped back to the absolute path of the "same" file (though
+	   not necessarily the same original path) using absolute_path().
+
+	   This function may only be called within the context of
+	   LV2_State_Interface methods.  The caller is responsible for freeing the
+	   returned value with free().
+	*/
+	char* (*abstract_path)(LV2_State_Map_Path_Handle handle,
+	                       const char*               absolute_path);
+
+	/**
+	   Map an abstract path from plugin state to an absolute path.
+	   @param handle MUST be the `handle` member of this struct.
+	   @param abstract_path An abstract path (e.g. a path from plugin state).
+	   @return An absolute file system path.
+
+	   The plugin MUST use this function in order to actually open or otherwise
+	   use any paths loaded from plugin state.
+
+	   This function may only be called within the context of
+	   LV2_State_Interface methods.  The caller is responsible for freeing the
+	   returned value with free().
+	*/
+	char* (*absolute_path)(LV2_State_Map_Path_Handle handle,
+	                       const char*               abstract_path);
+} LV2_State_Map_Path;
+
+/**
+   Feature data for state:makePath (@ref LV2_STATE__makePath).
+*/
+typedef struct {
+	/**
+	   Opaque host data.
+	*/
+	LV2_State_Make_Path_Handle handle;
+
+	/**
+	   Return a path the plugin may use to create a new file.
+	   @param handle MUST be the `handle` member of this struct.
+	   @param path The path of the new file within a namespace unique to this
+	   plugin instance.
+	   @return The absolute path to use for the new file.
+
+	   This function can be used by plugins to create files and directories,
+	   either at state saving time (if this feature is passed to
+	   LV2_State_Interface.save()) or any time (if this feature is passed to
+	   LV2_Descriptor.instantiate()).
+
+	   The host MUST do whatever is necessary for the plugin to be able to
+	   create a file at the returned path (e.g. using fopen), including
+	   creating any leading directories.
+
+	   If this function is passed to LV2_Descriptor.instantiate(), it may be
+	   called from any non-realtime context.  If it is passed to
+	   LV2_State_Interface.save(), it may only be called within the dynamic
+	   scope of that function call.
+
+	   The caller is responsible for freeing the returned value with free().
+	*/
+	char* (*path)(LV2_State_Make_Path_Handle handle,
+	              const char*                path);
+} LV2_State_Make_Path;
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* LV2_STATE_H */
+
+/**
+   @}
+*/
diff --git a/lv2/state/state.ttl b/lv2/state/state.ttl
new file mode 100644
index 0000000..c86fea7
--- /dev/null
+++ b/lv2/state/state.ttl
@@ -0,0 +1,382 @@
+@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 state: <http://lv2plug.in/ns/ext/state#> .
+
+<http://lv2plug.in/ns/ext/state>
+	a lv2:Specification ;
+	rdfs:seeAlso <state.h> ,
+		<lv2-state.doap.ttl> ;
+	lv2:documentation """
+<p>This extension defines a simple mechanism which allows hosts to save and
+restore a plugin instance's state.  The goal is for an instance's state to be
+<em>completely</em> described by port values (as with all LV2 plugins) and a
+simple dictionary.</p>
+
+<p>The <q>state</q> defined here is conceptually a key:value dictionary, with
+URI keys and values of any type.  For performance reasons the key and value
+type are actually a <q>URID</q>, a URI mapped to an integer.  A single
+key:value pair is called a <q>property</q>.</p>
+
+<p>This state model is simple yet has many benefits:</p>
+<ul>
+  <li>Both fast and extensible thanks to URID keys.</li>
+  <li>No limitations on possible value types.</li>
+  <li>Easy to serialise in almost any format.</li>
+  <li>Easy to store in a typical <q>map</q> or <q>dictionary</q> data
+  structure.</li>
+  <li>Elegantly described in Turtle, so state can be described in LV2 data
+  files (including presets).</li>
+  <li>Does not impose any file formats, data structures, or file system
+  requirements.</li>
+  <li>Suitable for portable persistent state as well as fast in-memory
+  snapshots.</li>
+  <li>Keys <em>may</em> be well-defined and used meaningfully across several
+  implementations.</li>
+  <li>State <em>may</em> be dynamic, but plugins are not required to have a
+  dynamic dictionary data structure available.</li>
+</ul>
+
+<p>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.</p>
+
+<p>Since value types are defined by URI, any type is possible.  However, a set
+of standard types is defined by the <a href="../atom/atom.html">LV2 Atom</a>
+extension.  Use of these types is recommended.  Hosts MUST implement at least
+<a href="../atom/atom.html#String">atom:String</a>, which is simply a C
+string.</p>
+
+<h3>Referring to Files</h3>
+
+<p>Plugins may need to refer to existing 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.  Plugins MUST use the type <a
+href="../atom/atom.html#Path">atom:Path</a> for all paths in their state.</p>
+
+<p>Plugins are strongly encouraged to avoid creating files, instead storing all
+state as properties.  However, occasionally the ability to create files is
+necessary.  To make this possible, the host can provide the feature
+state:makePath which allocates paths for plugin-created files.  Plugins MUST
+NOT create files in any other locations.</p>
+
+<h3>Plugin Code Example</h3>
+
+<pre class="c-code">
+
+/* Namespace for this plugin's keys.  This SHOULD be something that could be
+   published as a document, even if that document does not exist right now.
+*/
+#define NS_MY "http://example.org/myplugin/schema#"
+
+#define DEFAULT_GREETING "Hello"
+
+LV2_Handle
+my_instantiate(...)
+{
+    MyPlugin* plugin = ...;
+    plugin->uris.atom_String = map_uri(LV2_ATOM__String);
+    plugin->uris.my_greeting = map_uri(NS_MY "greeting");
+    plugin->state.greeting   = strdup(DEFAULT_GREETING);
+    return plugin;
+}
+
+LV2_State_Status
+my_save(LV2_Handle                 instance,
+        LV2_State_Store_Function   store,
+        LV2_State_Handle           handle,
+        uint32_t                   flags,
+        const LV2_Feature *const * features)
+{
+    MyPlugin*   plugin   = (MyPlugin*)instance;
+    const char* greeting = plugin->state.greeting;
+
+    store(handle,
+          plugin->uris.my_greeting,
+          greeting,
+          strlen(greeting) + 1,  // Careful!  Need space for terminator
+          plugin->uris.atom_String,
+          LV2_STATE_IS_POD | LV2_STATE_IS_PORTABLE);
+
+    return LV2_STATE_SUCCESS;
+}
+
+LV2_State_Status
+my_restore(LV2_Handle                  instance,
+           LV2_State_Retrieve_Function retrieve,
+           LV2_State_Handle            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.my_greeting, &amp;size, &amp;type, &amp;flags);
+
+    if (greeting) {
+        free(plugin->state->greeting);
+        plugin->state->greeting = strdup(greeting);
+    } else {
+        plugin->state->greeting = strdup(DEFAULT_GREETING);
+    }
+
+    return LV2_STATE_SUCCESS;
+}
+
+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)) {
+        return &amp;state_iface;
+    }
+}
+</pre>
+
+<h3>Host Code Example</h3>
+
+<pre class="c-code">
+LV2_State_Status
+store_callback(LV2_State_Handle handle,
+               uint32_t         key,
+               const void*      value,
+               size_t           size,
+               uint32_t         type,
+               uint32_t         flags)
+{
+    if ((flags &amp; LV2_STATE_IS_POD)) {
+        /* We only care about POD since we're keeping state in memory only.
+           For disk or network use, LV2_STATE_IS_PORTABLE must also be checked.
+        */
+        Map* state_map = (Map*)handle;
+        state_map->insert(key, Value(copy(value), size, type));
+        return 0;
+    } else {
+        return 1; /* Non-POD events are unsupported. */
+    }
+}
+
+Map
+get_plugin_state(LV2_Handle instance)
+{
+    LV2_State* state = instance.extension_data(LV2_STATE__interface);
+    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>
+
+<h3>Extensions to this Specification</h3>
+
+<p>It is likely that other interfaces for working with plugin state will be
+developed as needed.  This is encouraged, however everything SHOULD work within
+the state <em>model</em> defined here.  That is, <strong>do not complicate the
+state model</strong>.  Implementations can assume the following:</p>
+
+<ul>
+<li>The current port values and state dictionary completely describe a plugin
+instance, at least well enough that saving and restoring will yield an
+<q>identical</q> instance from the user's perspective.</li>
+<li>Hosts are not expected to save and/or restore any other attributes of a
+plugin instance.</li>
+</ul>
+
+<h3>The <q>Property Principle</q></h3>
+
+<p>The main benefit of this meaningful state model is that it can double as a
+plugin control/query mechanism.  For plugins that require more advanced control
+than simple control ports, instead of defining a set of commands, define
+properties whose values can be set appropriately.  This provides both a way to
+control and save that state <q>for free</q>, since there is no need to define
+commands <em>and</em> a set of properties for storing their effects.  In
+particular, this is a good way for UIs to achieve more advanced control of
+plugins.</p>
+
+<p>This <q>property principle</q> is summed up in the phrase:
+<q>Don't stop; set playing to false</q>.</p>
+
+<p>This extension does not define a dynamic mechanism for state access and
+manipulation.  The <a href="../patch/patch.html">LV2 Patch</a> extension
+defines a generic set of messages which can be used to access or manipulate
+properties, and the <a href="../atom/atom.html">LV2 Atom</a> extension defines
+a port type and data container capable of transmitting those messages.</p>
+""" .
+
+state:interface
+	a lv2:ExtensionData ;
+	lv2:documentation """
+<p>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
+LV2_STATE__interface.</p>
+
+<p>The plugin data file should describe this like so:</p>
+<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:State
+	a rdfs:Class ;
+	rdfs:label "State" ;
+	lv2:documentation """
+<p>A state dictionary.  This type should be used wherever instance state is
+described.  The properties of a resource with this type correspond directly to
+the properties of the state dictionary (except the property that states it has
+this type).</p>
+""" .
+
+state:loadDefaultState
+	a lv2:Feature ;
+	lv2:documentation """
+<p>This feature indicates that the plugin has default state listed with the
+state:state property which should be loaded by the host before running the
+plugin.  Requiring this feature allows plugins to implement a single state
+loading mechanism which works for initialisation as well as restoration,
+without having to hard-code default state.</p>
+
+<p>To support this feature, the host MUST <q>restore</q> the default state
+after instantiating the plugin but before calling run().</p>
+""" .
+
+state:state
+	a rdf:Property ;
+	rdfs:label "state" ;
+	rdfs:range state:State ;
+	lv2:documentation """
+<p>The state of this instance.  This property may be used anywhere a state
+needs to be described, for example:</p>
+
+<pre class="turtle-code">
+@prefix eg: &lt;http://example.org/&gt; .
+
+&lt;plugin-instance&gt;
+    state:state [
+        eg:somekey "some value" ;
+        eg:someotherkey "some other value" ;
+        eg:favourite-number 2
+    ] .
+</pre>
+""" .
+
+state:mapPath
+	a lv2:Feature ;
+	rdfs:label "map file paths" ;
+	lv2:documentation """
+<p>This feature maps absolute paths to/from <q>abstract paths</q> which are
+stored in state.  To support this feature a host must pass an LV2_Feature with
+URI LV2_STATE__mapPath and data pointed to an LV2_State_Map_Path to the
+plugin's LV2_State_Interface methods.</p>
+
+<p>The plugin MUST map <em>all</em> paths stored in its state (including those
+inside any files in its state).  This is necessary to enable host to handle
+file system references correctly, e.g. for distribution or archival.</p>
+
+<p>For example, a plugin may write a path to a state file like so:</p>
+
+<pre class="c-code">
+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);
+}
+</pre>
+
+<p>Then, later reload the path like so:</p>
+
+<pre class="c-code">
+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);
+}
+</pre>
+""" .
+
+state:makePath
+	a lv2:Feature ;
+	rdfs:label "create new file paths" ;
+	lv2:documentation """
+<p>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__makePath 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.</p>
+
+<p>The plugin is guaranteed a hierarchical namespace unique to that plugin
+instance, and may expect the returned path to have the requested path as a
+suffix.  There is <em>one</em> such namespace, even if the feature is passed to
+both LV2_Descriptor::instantiate() <em>and</em> LV2_State_Interface::save().
+Beyond this, the plugin MUST NOT make any assumptions about the returned
+paths.</p>
+
+<p>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.</p>
+
+<p>For example, a plugin may create a file in a subdirectory like so:</p>
+
+<pre class="c-code">
+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, "I am some data");
+    fclose(myfile);
+    return path;
+}
+</pre>
+""" .
+
+state:threadSafeRestore
+	a lv2:Feature ;
+	rdfs:label "thread-safe restore" ;
+	lv2:documentation """
+<p>If a plugin supports this feature, its LV2_State_Interface::restore method
+is thread-safe and may be called concurrently with audio class functions.</p>
+
+<p>To support this feature, the host MUST pass a <a
+href="../worker/worker.html#schedule">work:schedule</a> feature to the restore
+method, which will be used to complete the state restoration.  The usual
+mechanics of the worker apply: the host will call the plugin's work method,
+which emits a response which is later applied in the audio thread.</p>
+
+<p>The host is not required to block run() while restore() and work() load the
+state, so this feature allows state to be restored without dropouts.</p>
+""" .
+
+state:Changed
+	a rdfs:Class ;
+	rdfs:label "State changed" ;
+	lv2:documentation """
+<p>A notification that the internal state of the plugin has been changed in a
+way that the host can not otherwise know about.</p>
+
+<p>This is a one-way notification, intended to be used as the type of an <a
+href="../atom/atom.html#Object">Object</a> sent from plugins when
+necessary.</p>
+
+<p>Plugins SHOULD emit such an event whenever a change has occurred that would
+result in a different state being saved, but not when the host explicity makes
+a change which it knows is likely to have that effect, such as changing a
+parameter.</p>
+""" .