Add LilvState API for handling plugin state. This makes it simple to save and

restore plugin state both in memory and on disk, as well as save presets in a
host-sharable way since the disk format is identical to the LV2 presets format.


git-svn-id: http://svn.drobilla.net/lad/trunk/lilv@3899 a436a847-0d15-0410-975c-d299462d15a1

5 files changed, 824 insertions, 23 deletions

diff --git a/src/lilv_internal.h b/src/lilv_internal.h
index a700d6f..75e21a2 100644
--- a/src/lilv_internal.h
+++ b/src/lilv_internal.h
@@ -65,7 +65,6 @@ struct LilvPortImpl {
 	LilvNodes* classes;  ///< rdf:type
 };
 
-
 struct LilvSpecImpl {
 	SordNode*            spec;
 	SordNode*            bundle;
@@ -132,6 +131,7 @@ struct LilvWorldImpl {
 	LilvNodes*         loaded_files;
 	SordNode*          dc_replaces_node;
 	SordNode*          dyn_manifest_node;
+	SordNode*          lv2_appliesTo_node;
 	SordNode*          lv2_binary_node;
 	SordNode*          lv2_default_node;
 	SordNode*          lv2_index_node;
@@ -143,6 +143,7 @@ struct LilvWorldImpl {
 	SordNode*          lv2_reportslatency_node;
 	SordNode*          lv2_specification_node;
 	SordNode*          lv2_symbol_node;
+	SordNode*          pset_value_node;
 	SordNode*          rdf_a_node;
 	SordNode*          rdf_value_node;
 	SordNode*          rdfs_class_node;
@@ -154,7 +155,6 @@ struct LilvWorldImpl {
 	SordNode*          xsd_double_node;
 	SordNode*          xsd_integer_node;
 	LilvNode*          doap_name_val;
-	LilvNode*          lv2_applies_to_val;
 	LilvNode*          lv2_extensionData_val;
 	LilvNode*          lv2_name_val;
 	LilvNode*          lv2_optionalFeature_val;
@@ -290,6 +290,13 @@ lilv_match_subject(SordIter* iter) {
 }
 
 static inline const SordNode*
+lilv_match_predicate(SordIter* iter) {
+	SordQuad tup;
+	sord_iter_get(iter, tup);
+	return tup[SORD_PREDICATE];
+}
+
+static inline const SordNode*
 lilv_match_object(SordIter* iter) {
 	SordQuad tup;
 	sord_iter_get(iter, tup);
diff --git a/src/plugin.c b/src/plugin.c
index b305291..fd4b300 100644
--- a/src/plugin.c
+++ b/src/plugin.c
@@ -670,7 +670,7 @@ lilv_plugin_has_extension_data(const LilvPlugin* p,
 		return false;
 	}
 }
-	
+
 LILV_API
 LilvNodes*
 lilv_plugin_get_extension_data(const LilvPlugin* p)
@@ -833,8 +833,11 @@ LilvNodes*
 lilv_plugin_get_related(const LilvPlugin* plugin, const LilvNode* type)
 {
 	LilvWorld* const world   = plugin->world;
-	LilvNodes* const related = lilv_world_find_nodes(
-		world, NULL, world->lv2_applies_to_val, lilv_plugin_get_uri(plugin));
+	LilvNodes* const related = lilv_world_query_values_internal(
+		world,
+		NULL,
+		world->lv2_appliesTo_node,
+		lilv_plugin_get_uri(plugin)->val.uri_val);
 
 	if (!type) {
 		return related;
@@ -857,13 +860,6 @@ lilv_plugin_get_related(const LilvPlugin* plugin, const LilvNode* type)
 	return matches;
 }
 
-static size_t
-file_sink(const void* buf, size_t len, void* stream)
-{
-	FILE* file = (FILE*)stream;
-	return fwrite(buf, 1, len, file);
-}
-
 static SerdEnv*
 new_lv2_env(const SerdNode* base)
 {
@@ -910,7 +906,7 @@ lilv_plugin_write_description(LilvWorld*        world,
 		SERD_STYLE_ABBREVIATED|SERD_STYLE_CURIED,
 		env,
 		NULL,
-		file_sink,
+		serd_file_sink,
 		plugin_file);
 
 	// Write prefixes if this is a new file
@@ -950,7 +946,7 @@ lilv_plugin_write_manifest_entry(LilvWorld*        world,
 		SERD_STYLE_ABBREVIATED|SERD_STYLE_CURIED,
 		env,
 		NULL,
-		file_sink,
+		serd_file_sink,
 		manifest_file);
 
 	// Write prefixes if this is a new file
diff --git a/src/state.c b/src/state.c
new file mode 100644
index 0000000..aae3fab
--- /dev/null
+++ b/src/state.c
@@ -0,0 +1,794 @@
+/*
+  Copyright 2007-2011 David Robillard <http://drobilla.net>
+
+  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.
+*/
+
+#define _POSIX_SOURCE 1  /* for fileno */
+#define _BSD_SOURCE   1  /* for lockf */
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "lilv-config.h"
+#include "lilv_internal.h"
+
+#ifdef HAVE_LV2_STATE
+#    include "lv2/lv2plug.in/ns/ext/state/state.h"
+#endif
+
+#if defined(HAVE_LOCKF) && defined(HAVE_FILENO)
+#    include <unistd.h>
+#endif
+
+#ifdef HAVE_MKDIR
+#    include <sys/stat.h>
+#    include <sys/types.h>
+#endif
+
+#define NS_ATOM  "http://lv2plug.in/ns/ext/atom#"
+#define NS_PSET  "http://lv2plug.in/ns/ext/presets#"
+#define NS_STATE "http://lv2plug.in/ns/ext/state#"
+
+#define USTR(s) ((const uint8_t*)(s))
+
+typedef struct {
+	void*    value;
+	size_t   size;
+	uint32_t key;
+	uint32_t type;
+	uint32_t flags;
+} Property;
+
+typedef struct {
+	char*     symbol;
+	LilvNode* value;
+} PortValue;
+
+struct LilvStateImpl {
+	LilvNode*  plugin_uri;
+	Property*  props;
+	PortValue* values;
+	char*      label;
+	uint32_t   num_props;
+	uint32_t   num_values;
+};
+
+static int
+property_cmp(const void* a, const void* b)
+{
+	const Property* pa = (const Property*)a;
+	const Property* pb = (const Property*)b;
+	return pa->key - pb->key;
+}
+
+LILV_API
+const LilvNode*
+lilv_state_get_plugin_uri(const LilvState* state)
+{
+	return state->plugin_uri;
+}
+
+static PortValue*
+append_port_value(LilvState*  state,
+                  const char* port_symbol,
+                  LilvNode*   value)
+{
+	state->values = realloc(state->values,
+	                        (++state->num_values) * sizeof(PortValue));
+	PortValue* pv = &state->values[state->num_values - 1];
+	pv->symbol = lilv_strdup(port_symbol);
+	pv->value  = value;
+	return pv;
+}
+
+LILV_API
+const char*
+lilv_state_get_label(const LilvState* state)
+{
+	return state->label;
+}
+
+LILV_API
+void
+lilv_state_set_label(LilvState*  state,
+                     const char* label)
+{
+	if (state->label) {
+		free(state->label);
+	}
+
+	state->label = label ? lilv_strdup(label) : NULL;
+}
+
+#ifdef HAVE_LV2_STATE
+static 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)) {
+		// TODO: A flag so we know if we can hold a reference would be nice
+		LILV_WARN("Non-POD property ignored.\n");
+		return 1;
+	}
+
+	LilvState* const state = (LilvState*)handle;
+	state->props = realloc(state->props,
+	                       (++state->num_props) * sizeof(Property));
+	Property* const prop = &state->props[state->num_props - 1];
+	
+	prop->value = malloc(size);
+	memcpy(prop->value, value, size);
+
+	prop->size  = size;
+	prop->key   = key;
+	prop->type  = type;
+	prop->flags = flags;
+
+	return 0;
+}
+#endif  // HAVE_LV2_STATE
+
+LILV_API
+LilvState*
+lilv_state_new_from_instance(const LilvPlugin*          plugin,
+                             LilvInstance*              instance,
+                             LilvGetPortValueFunc       get_value,
+                             void*                      user_data,
+                             uint32_t                   flags,
+                             const LV2_Feature *const * features)
+{
+	LilvWorld* const world = plugin->world;
+	LilvState* const state = malloc(sizeof(LilvState));
+	memset(state, '\0', sizeof(LilvState));
+	state->plugin_uri = lilv_node_duplicate(lilv_plugin_get_uri(plugin));
+
+	// Store port values
+	LilvNode* lv2_ControlPort = lilv_new_uri(world, LILV_URI_CONTROL_PORT);
+	LilvNode* lv2_InputPort   = lilv_new_uri(world, LILV_URI_INPUT_PORT);
+	for (uint32_t i = 0; i < plugin->num_ports; ++i) {
+		const LilvPort* const port = plugin->ports[i];
+		if (lilv_port_is_a(plugin, port, lv2_ControlPort)
+		    && lilv_port_is_a(plugin, port, lv2_InputPort)) {
+			const char* sym = lilv_node_as_string(port->symbol);
+			append_port_value(state, sym, get_value(sym, user_data));
+		}
+	}
+	lilv_node_free(lv2_ControlPort);
+	lilv_node_free(lv2_InputPort);
+
+	// Store properties
+#ifdef HAVE_LV2_STATE
+	const LV2_Descriptor*      descriptor = instance->lv2_descriptor;
+	const LV2_State_Interface* iface      = (descriptor->extension_data)
+		? descriptor->extension_data(LV2_STATE_INTERFACE_URI)
+		: NULL;
+
+	iface->save(instance->lv2_handle, store_callback, state, flags, features);
+#endif  // HAVE_LV2_STATE
+
+	qsort(state->props, state->num_props, sizeof(Property), property_cmp);
+
+	return state;
+}
+
+static const void*
+retrieve_callback(void*     handle,
+                  uint32_t  key,
+                  size_t*   size,
+                  uint32_t* type,
+                  uint32_t* flags)
+{
+	const LilvState* const state      = (LilvState*)handle;
+	const Property         search_key = { NULL, 0, key, 0, 0 };
+	const Property* const  prop       = (Property*)bsearch(
+		&search_key, state->props, state->num_props,
+		sizeof(Property), property_cmp);
+
+	if (prop) {
+		*size  = prop->size;
+		*type  = prop->type;
+		*flags = prop->flags;
+		return prop->value;
+	}
+	return NULL;
+}
+
+LILV_API
+void
+lilv_state_restore(const LilvState*           state,
+                   LilvInstance*              instance,
+                   LilvSetPortValueFunc       set_value,
+                   void*                      user_data,
+                   uint32_t                   flags,
+                   const LV2_Feature *const * features)
+{
+#ifdef HAVE_LV2_STATE
+	const LV2_Descriptor*      descriptor = instance->lv2_descriptor;
+	const LV2_State_Interface* iface      = (descriptor->extension_data)
+		? descriptor->extension_data(LV2_STATE_INTERFACE_URI)
+		: NULL;
+
+	iface->restore(instance->lv2_handle, retrieve_callback,
+	               (LV2_State_Handle)state, flags, features);
+
+	if (set_value) {
+		for (uint32_t i = 0; i < state->num_values; ++i) {
+			set_value(state->values[i].symbol,
+			          state->values[i].value,
+			          user_data);
+		}
+	}
+#endif  // HAVE_LV2_STATE
+}
+
+static SordNode*
+get_one(SordModel* model, const SordNode* s, const SordNode* p)
+{
+	const SordQuad  pat  = { s, p, NULL, NULL };
+	SordIter* const i    = sord_find(model, pat);
+	SordNode* const node = i ? sord_node_copy(lilv_match_object(i)) : NULL;
+	sord_iter_free(i);
+	return node;
+}
+
+static void
+property_from_node(LilvWorld*      world,
+                   LV2_URID_Map*   map,
+                   const LilvNode* node,
+                   Property*       prop)
+{
+	const char* str = lilv_node_as_string(node);
+	switch (node->type) {
+	case LILV_VALUE_URI:
+		prop->value = malloc(sizeof(uint32_t));
+		*(uint32_t*)prop->value = map->map(map->handle, str);
+		prop->type = map->map(map->handle, NS_ATOM "URID");
+		prop->size = sizeof(uint32_t);
+		break;
+	case LILV_VALUE_BLANK:
+		// TODO: Hmm...
+		break;
+	case LILV_VALUE_STRING:
+		prop->size = strlen(str) + 1;
+		prop->value = malloc(prop->size);
+		memcpy(prop->value, str, prop->size + 1);
+		prop->type = map->map(map->handle, NS_ATOM "String");
+		break;
+	case LILV_VALUE_BOOL:
+		prop->value = malloc(sizeof(uint32_t));
+		*(uint32_t*)prop->value = lilv_node_as_bool(node) ? 1 : 0;
+		prop->type = map->map(map->handle, NS_ATOM "Bool");
+		prop->size = sizeof(uint32_t);
+		break;
+	case LILV_VALUE_INT:
+		prop->value = malloc(sizeof(uint32_t));
+		*(uint32_t*)prop->value = lilv_node_as_int(node);
+		prop->type = map->map(map->handle, NS_ATOM "Int32");
+		prop->size = sizeof(uint32_t);
+		break;
+	case LILV_VALUE_FLOAT:
+		prop->value = malloc(sizeof(float));
+		*(float*)prop->value = lilv_node_as_float(node);
+		prop->type = map->map(map->handle, NS_ATOM "Float");
+		prop->size = sizeof(float);
+		break;
+	}
+	prop->flags = LV2_STATE_IS_POD|LV2_STATE_IS_PORTABLE;
+}
+
+static LilvState*
+new_state_from_model(LilvWorld*      world,
+                     LV2_URID_Map*   map,
+                     SordModel*      model,
+                     const SordNode* node)
+{
+	LilvState* const state = malloc(sizeof(LilvState));
+	memset(state, '\0', sizeof(LilvState));
+
+	// Get the plugin URI this state applies to
+	const SordQuad pat1 = {
+		node, world->lv2_appliesTo_node, NULL, NULL };
+	SordIter* i = sord_find(model, pat1);
+	if (i) {
+		state->plugin_uri = lilv_node_new_from_node(
+			world, lilv_match_object(i));
+		sord_iter_free(i);
+	} else {
+		LILV_ERRORF("State %s missing lv2:appliesTo property\n",
+		            sord_node_get_string(node));
+	}
+
+	// Get port values
+	const SordQuad pat2 = { node, world->lv2_port_node, NULL, NULL };
+	SordIter* ports = sord_find(model, pat2);
+	FOREACH_MATCH(ports) {
+		const SordNode* port   = lilv_match_object(ports);
+		const SordNode* label  = get_one(model, port, world->rdfs_label_node);
+		const SordNode* symbol = get_one(model, port, world->lv2_symbol_node);
+		const SordNode* value  = get_one(model, port, world->pset_value_node);
+		if (!symbol) {
+			LILV_ERRORF("State `%s' port missing symbol.\n",
+			            sord_node_get_string(node));
+		} else if (!value) {
+			LILV_ERRORF("State `%s' port `%s' missing value.\n",
+			            sord_node_get_string(symbol),
+			            sord_node_get_string(node));
+		} else {
+			const char* sym    = (const char*)sord_node_get_string(symbol);
+			LilvNode*   lvalue = lilv_node_new_from_node(world, value);
+			append_port_value(state, sym, lvalue);
+
+			if (label) {
+				lilv_state_set_label(
+					state, (const char*)sord_node_get_string(label));
+			}
+		}
+	}
+	sord_iter_free(ports);
+
+	// Get properties
+	SordNode* statep = sord_new_uri(world->world, USTR(NS_STATE "state"));
+	const SordNode* state_node = get_one(model, node, statep);
+	if (state_node) {
+		const SordQuad pat3  = { state_node, NULL, NULL };
+		SordIter*      props = sord_find(model, pat3);
+		FOREACH_MATCH(props) {
+			const SordNode* p     = lilv_match_predicate(props);
+			const SordNode* o     = lilv_match_object(props);
+			LilvNode*       onode = lilv_node_new_from_node(world, o);
+			
+			Property prop = { NULL, 0, 0, 0, 0 };
+			prop.key      = map->map(map->handle,
+			                         (const char*)sord_node_get_string(p));
+			property_from_node(world, map, onode, &prop);
+			if (prop.value) {
+				state->props = realloc(
+					state->props, (++state->num_props) * sizeof(Property));
+				state->props[state->num_props - 1] = prop;
+			}
+
+			lilv_node_free(onode);
+		}
+		sord_iter_free(props);
+	}
+	sord_node_free(world->world, statep);
+
+	qsort(state->props, state->num_props, sizeof(Property), property_cmp);
+	
+	return state;
+}
+
+LILV_API
+LilvState*
+lilv_state_new_from_world(LilvWorld*      world,
+                          LV2_URID_Map*   map,
+                          const LilvNode* node)
+{
+	if (!lilv_node_is_uri(node) && !lilv_node_is_blank(node)) {
+		LILV_ERRORF("Subject `%s' is not a URI or blank node.\n",
+		            lilv_node_as_string(node));
+		return NULL;
+	}
+
+	return new_state_from_model(world, map, world->model, node->val.uri_val);
+}
+
+LILV_API
+LilvState*
+lilv_state_new_from_file(LilvWorld*      world,
+                         LV2_URID_Map*   map,
+                         const LilvNode* subject,
+                         const char*     path)
+{
+	if (subject && !lilv_node_is_uri(subject)
+	    && !lilv_node_is_blank(subject)) {
+		LILV_ERRORF("Subject `%s' is not a URI or blank node.\n",
+		            lilv_node_as_string(subject));
+		return NULL;
+	}
+
+	uint8_t*    uri    = (uint8_t*)lilv_strjoin("file://", path, NULL);
+	SerdNode    base   = serd_node_from_string(SERD_URI, uri);
+	SerdEnv*    env    = serd_env_new(&base);
+	SordModel*  model  = sord_new(world->world, SORD_SPO, false);
+	SerdReader* reader = sord_new_reader(model, env, SERD_TURTLE, NULL);
+
+	serd_reader_read_file(reader, uri);
+
+	SordNode* subject_node = (subject)
+		? subject->val.uri_val
+		: sord_node_from_serd_node(world->world, env, &base, NULL, NULL);
+
+	LilvState* state = new_state_from_model(world, map, model, subject_node);
+
+	serd_reader_free(reader);
+	sord_free(model);
+	serd_env_free(env);
+	free(uri);
+	return state;
+}
+
+static LilvNode*
+node_from_property(LilvWorld* world, const char* type, void* value, size_t size)
+{
+	if (!strcmp(type, NS_ATOM "String")) {
+		return lilv_new_string(world, (const char*)value);
+	} else if (!strcmp(type, NS_ATOM "Int32")) {
+		if (size == sizeof(int32_t)) {
+			return lilv_new_int(world, *(int32_t*)value);
+		} else {
+			LILV_WARNF("Int32 property <%s> has size %zu\n", type, size);
+		}
+	} else if (!strcmp(type, NS_ATOM "Float")) {
+		if (size == sizeof(float)) {
+			return lilv_new_float(world, *(float*)value);
+		} else {
+			LILV_WARNF("Float property <%s> has size %zu\n", type, size);
+		}
+	} else if (!strcmp(type, NS_ATOM "Bool")) {
+		if (size == sizeof(int32_t)) {
+			return lilv_new_bool(world, *(int32_t*)value);
+		} else {
+			LILV_WARNF("Bool property <%s> has size %zu\n", type, size);
+		}
+	}
+	return NULL;
+}
+
+static void
+node_to_serd(const LilvNode* node, SerdNode* value, SerdNode* type)
+{
+	const char* type_uri = NULL;
+	switch (node->type) {
+	case LILV_VALUE_URI:
+		*value = serd_node_from_string(SERD_URI, USTR(node->str_val));
+		break;
+	case LILV_VALUE_BLANK:
+		*value = serd_node_from_string(SERD_BLANK, USTR(node->str_val));
+		break;
+	default:
+		*value = serd_node_from_string(SERD_LITERAL, USTR(node->str_val));
+		switch (node->type) {
+		case LILV_VALUE_BOOL:
+			type_uri = LILV_NS_XSD "boolean";
+			break;
+		case LILV_VALUE_INT:
+			type_uri = LILV_NS_XSD "integer";
+			break;
+		case LILV_VALUE_FLOAT:
+			type_uri = LILV_NS_XSD "decimal";
+			break;
+		default:
+			break;
+		}
+	}
+	*type = (type_uri)
+		? serd_node_from_string(SERD_URI, USTR(type_uri))
+		: SERD_NODE_NULL;
+}
+
+static int
+add_state_to_manifest(const LilvNode* plugin_uri,
+                      const char*     manifest_path,
+                      const char*     state_uri,
+                      const char*     state_file_uri)
+{
+	FILE* fd = fopen((char*)manifest_path, "a");
+	if (!fd) {
+		fprintf(stderr, "error: Failed to open %s (%s)\n",
+		        manifest_path, strerror(errno));
+		return 4;
+	}
+
+	// Make path relative if it is in the same directory as manifest
+	const char* last_slash = strrchr(state_file_uri, '/');
+	if (last_slash) {
+		const size_t len = last_slash - state_file_uri;
+		if (!strncmp(manifest_path, state_file_uri, len)) {
+			state_file_uri = last_slash + 1;
+		}
+	}
+
+	SerdEnv* env = serd_env_new(NULL);
+	serd_env_set_prefix_from_strings(env, USTR("lv2"),  USTR(LILV_NS_LV2));
+	serd_env_set_prefix_from_strings(env, USTR("pset"), USTR(NS_PSET));
+	serd_env_set_prefix_from_strings(env, USTR("rdfs"), USTR(LILV_NS_RDFS));
+
+#if defined(HAVE_LOCKF) && defined(HAVE_FILENO)
+	lockf(fileno(fd), F_LOCK, 0);
+#endif
+
+	char* const manifest_uri = lilv_strjoin("file://", manifest_path, NULL);
+
+	SerdURI base_uri;
+	SerdNode base = serd_node_new_uri_from_string(
+		(const uint8_t*)manifest_uri, NULL, &base_uri);
+
+	SerdWriter* writer = serd_writer_new(
+		SERD_TURTLE, SERD_STYLE_ABBREVIATED|SERD_STYLE_CURIED,
+		env, &base_uri,
+		serd_file_sink,
+		fd);
+
+	fseek(fd, 0, SEEK_END);
+	if (ftell(fd) == 0) {
+		serd_env_foreach(env, (SerdPrefixSink)serd_writer_set_prefix, writer);
+	} else {
+		fprintf(fd, "\n");
+	}
+
+	if (!state_uri) {
+		state_uri = state_file_uri;
+	}
+
+	SerdNode s    = serd_node_from_string(SERD_URI, USTR(state_uri));
+	SerdNode file = serd_node_from_string(SERD_URI, USTR(state_file_uri));
+
+	// <state> a pset:Preset
+	SerdNode p = serd_node_from_string(SERD_URI, USTR(LILV_NS_RDF "type"));
+	SerdNode o = serd_node_from_string(SERD_CURIE, USTR("pset:Preset"));
+	serd_writer_write_statement(writer, 0, NULL, &s, &p, &o, NULL, NULL);
+
+	// <state> rdfs:seeAlso <file>
+	p = serd_node_from_string(SERD_URI, USTR(LILV_NS_RDFS "seeAlso"));
+	serd_writer_write_statement(writer, 0, NULL, &s, &p, &file, NULL, NULL);
+
+	// <state> lv2:appliesTo <plugin>
+	p = serd_node_from_string(SERD_URI, USTR(LILV_NS_LV2 "appliesTo"));
+	o = serd_node_from_string(
+		SERD_URI, USTR(lilv_node_as_string(plugin_uri)));
+	serd_writer_write_statement(writer, 0, NULL, &s, &p, &o, NULL, NULL);
+
+	serd_writer_free(writer);
+	serd_node_free(&base);
+
+#ifdef HAVE_LOCKF
+	lockf(fileno(fd), F_ULOCK, 0);
+#endif
+
+	fclose(fd);
+	free(manifest_uri);
+	serd_env_free(env);
+
+	return 0;
+}
+
+static char*
+pathify(const char* in)
+{
+	const size_t in_len  = strlen(in);
+
+	char* out = calloc(in_len + 1, 1);
+	for (size_t i = 0; i < in_len; ++i) {
+		char c = in[i];
+		if (!((c >= 'a' && c <= 'z')
+		      || (c >= 'A' && c <= 'Z')
+		      || (c >= '0' && c <= '9'))) {
+			c = '-';
+		}
+		out[i] = c;
+	}
+	return out;
+}
+
+LILV_API
+int
+lilv_state_save(LilvWorld*       world,
+                LV2_URID_Unmap*  unmap,
+                const LilvState* state,
+                const char*      uri,
+                const char*      path,
+                const char*      manifest_path)
+{
+	char* default_path          = NULL;
+	char* default_manifest_path = NULL;
+	if (!path) {
+#ifdef HAVE_MKDIR
+		if (!state->label) {
+			LILV_ERROR("Attempt to save state with no label or path.\n");
+			return 1;
+		}
+
+		const char* const home = getenv("HOME");
+		if (!home) {
+			fprintf(stderr, "error: $HOME is undefined\n");
+			return 2;
+		}
+
+		// Create ~/.lv2/
+		char* const lv2dir = lilv_strjoin(home, "/.lv2/", NULL);
+		if (mkdir(lv2dir, 0755) && errno != EEXIST) {
+			fprintf(stderr, "error: Unable to create %s (%s)\n",
+			        lv2dir, strerror(errno));
+			free(lv2dir);
+			return 3;
+		}
+
+		// Create ~/.lv2/presets.lv2/
+		char* const bundle = lilv_strjoin(lv2dir, "presets.lv2/", NULL);
+		if (mkdir(bundle, 0755) && errno != EEXIST) {
+			fprintf(stderr, "error: Unable to create %s (%s)\n",
+			        lv2dir, strerror(errno));
+			free(lv2dir);
+			free(bundle);
+			return 4;
+		}
+		
+		char* const filename  = pathify(state->label);
+		default_path          = lilv_strjoin(bundle, filename, ".ttl", NULL);
+		default_manifest_path = lilv_strjoin(bundle, "manifest.ttl", NULL);
+
+		path          = default_path;
+		manifest_path = default_manifest_path;
+
+		free(lv2dir);
+		free(bundle);
+		free(filename);
+#else
+		LILV_ERROR("Save to default state path but mkdir is unavailable.\n");
+		return 1;
+#endif
+	}
+
+	FILE* fd = fopen(path, "w");
+	if (!fd) {
+		fprintf(stderr, "error: Failed to open %s (%s)\n",
+		        path, strerror(errno));
+		free(default_path);
+		free(default_manifest_path);
+		return 4;
+	}
+
+	SerdEnv* env = serd_env_new(NULL);
+	serd_env_set_prefix_from_strings(env, USTR("lv2"),   USTR(LILV_NS_LV2));
+	serd_env_set_prefix_from_strings(env, USTR("pset"),  USTR(NS_PSET));
+	serd_env_set_prefix_from_strings(env, USTR("rdfs"),  USTR(LILV_NS_RDFS));
+	serd_env_set_prefix_from_strings(env, USTR("state"), USTR(NS_STATE));
+
+	SerdNode lv2_appliesTo = serd_node_from_string(
+		SERD_CURIE, USTR("lv2:appliesTo"));
+
+	const SerdNode* plugin_uri = sord_node_to_serd_node(
+		state->plugin_uri->val.uri_val);
+
+	SerdNode subject = serd_node_from_string(SERD_URI, USTR(uri ? uri : ""));
+
+	SerdWriter* writer = serd_writer_new(
+		SERD_TURTLE,
+		SERD_STYLE_ABBREVIATED|SERD_STYLE_CURIED,
+		env,
+		&SERD_URI_NULL,
+		serd_file_sink,
+		fd);
+
+	serd_env_foreach(env, (SerdPrefixSink)serd_writer_set_prefix, writer);
+
+	// <subject> a pset:Preset
+	SerdNode p = serd_node_from_string(SERD_URI, USTR(LILV_NS_RDF "type"));
+	SerdNode o = serd_node_from_string(SERD_CURIE, USTR("pset:Preset"));
+	serd_writer_write_statement(writer, 0, NULL,
+	                            &subject, &p, &o, NULL, NULL);
+
+	// <subject> lv2:appliesTo <http://example.org/plugin>
+	serd_writer_write_statement(writer, 0, NULL,
+	                            &subject,
+	                            &lv2_appliesTo,
+	                            plugin_uri, NULL, NULL);
+
+	// <subject> rdfs:label label
+	if (state->label) {
+		p = serd_node_from_string(SERD_URI, USTR(LILV_NS_RDFS "label"));
+		o = serd_node_from_string(SERD_LITERAL, USTR(state->label));
+		serd_writer_write_statement(writer, 0,
+		                            NULL, &subject, &p, &o, NULL, NULL);
+	}
+
+	// Save port values
+	for (uint32_t i = 0; i < state->num_values; ++i) {
+		PortValue* const value = &state->values[i];
+
+		const SerdNode port = serd_node_from_string(
+			SERD_BLANK, USTR(value->symbol));
+
+		// <> lv2:port _:symbol
+		p = serd_node_from_string(SERD_URI, USTR(LILV_NS_LV2 "port"));
+		serd_writer_write_statement(writer, SERD_ANON_O_BEGIN,
+		                            NULL, &subject, &p, &port, NULL, NULL);
+
+		// _:symbol lv2:symbol "symbol"
+		p = serd_node_from_string(SERD_URI, USTR(LILV_NS_LV2 "symbol"));
+		o = serd_node_from_string(SERD_LITERAL, USTR(value->symbol));
+		serd_writer_write_statement(writer, SERD_ANON_CONT,
+		                            NULL, &port, &p, &o, NULL, NULL);
+
+		// _:symbol pset:value value
+		p = serd_node_from_string(SERD_URI, USTR(NS_PSET "value"));
+		SerdNode t;
+		node_to_serd(value->value, &o, &t);
+		serd_writer_write_statement(writer, SERD_ANON_CONT, NULL,
+		                            &port, &p, &o, &t, NULL);
+
+		serd_writer_end_anon(writer, &port);
+	}
+
+	// Save properties
+	const SerdNode state_node = serd_node_from_string(SERD_BLANK,
+	                                                  USTR("2state"));
+	if (state->num_props > 0) {
+		p = serd_node_from_string(SERD_URI, USTR(NS_STATE "state"));
+		serd_writer_write_statement(writer, SERD_ANON_O_BEGIN, NULL,
+		                            &subject, &p, &state_node, NULL, NULL);
+
+	}
+	for (uint32_t i = 0; i < state->num_props; ++i) {
+		Property*   prop = &state->props[i];
+		const char* key  = unmap->unmap(unmap->handle, prop->key);
+		const char* type = unmap->unmap(unmap->handle, prop->type);
+		if (!key) {
+			LILV_WARNF("Failed to unmap property key `%d'\n", prop->key);
+		} else if (!type) {
+			LILV_WARNF("Failed to unmap property type `%d'\n", prop->type);
+		} else if (!(prop->flags & LV2_STATE_IS_PORTABLE)) {
+			LILV_WARNF("Unable to save non-portable property <%s>\n", type);
+		} else {
+			LilvNode* const node = node_from_property(
+				world, type, prop->value, prop->size);
+			if (node) {
+				p = serd_node_from_string(SERD_URI, USTR(key));
+				SerdNode t;
+				node_to_serd(node, &o, &t);
+				serd_writer_write_statement(
+					writer, SERD_ANON_CONT, NULL,
+					&state_node, &p, &o, &t, NULL);
+			} else {
+				LILV_WARNF("Unable to save property type <%s>\n", type);
+			}
+		}
+	}
+	if (state->num_props > 0) {
+		serd_writer_end_anon(writer, &state_node);
+	}
+
+	// Close state file and clean up Serd
+	serd_writer_free(writer);
+	fclose(fd);
+	serd_env_free(env);
+
+	if (manifest_path) {
+		add_state_to_manifest(
+			state->plugin_uri, manifest_path, uri, path);
+	}
+
+	free(default_path);
+	free(default_manifest_path);
+	return 0;
+}
+
+LILV_API
+void
+lilv_state_free(LilvState* state)
+{
+	if (state) {
+		lilv_node_free(state->plugin_uri);
+		free(state->props);
+		free(state->values);
+		free(state->label);
+		free(state);
+	}
+}
diff --git a/src/world.c b/src/world.c
index ddcf5d1..af20bc3 100644
--- a/src/world.c
+++ b/src/world.c
@@ -14,7 +14,7 @@
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
-#define _POSIX_SOURCE 1
+#define _POSIX_SOURCE 1 /* for wordexp */
 
 #include <assert.h>
 #include <errno.h>
@@ -22,12 +22,13 @@
 #include <string.h>
 
 #include <dirent.h>
-#ifdef HAVE_WORDEXP
-#include <wordexp.h>
-#endif
 
 #include "lilv_internal.h"
 
+#ifdef HAVE_WORDEXP
+#    include <wordexp.h>
+#endif
+
 LILV_API
 LilvWorld*
 lilv_world_new(void)
@@ -48,14 +49,16 @@ lilv_world_new(void)
 	world->loaded_files   = zix_tree_new(
 		false, lilv_resource_node_cmp, NULL, (ZixDestroyFunc)lilv_node_free);
 
-#define NS_DYNMAN  "http://lv2plug.in/ns/ext/dynmanifest#"
 #define NS_DCTERMS "http://purl.org/dc/terms/"
+#define NS_DYNMAN  "http://lv2plug.in/ns/ext/dynmanifest#"
+#define NS_PSET    "http://lv2plug.in/ns/ext/presets#"
 
 #define NEW_URI(uri)     sord_new_uri(world->world, (const uint8_t*)uri)
 #define NEW_URI_VAL(uri) lilv_new_uri(world, (const char*)(uri));
 
 	world->dc_replaces_node         = NEW_URI(NS_DCTERMS   "replaces");
 	world->dyn_manifest_node        = NEW_URI(NS_DYNMAN    "DynManifest");
+	world->lv2_appliesTo_node       = NEW_URI(LILV_NS_LV2  "appliesTo");
 	world->lv2_binary_node          = NEW_URI(LILV_NS_LV2  "binary");
 	world->lv2_default_node         = NEW_URI(LILV_NS_LV2  "default");
 	world->lv2_index_node           = NEW_URI(LILV_NS_LV2  "index");
@@ -67,6 +70,7 @@ lilv_world_new(void)
 	world->lv2_reportslatency_node  = NEW_URI(LILV_NS_LV2  "reportsLatency");
 	world->lv2_specification_node   = NEW_URI(LILV_NS_LV2  "Specification");
 	world->lv2_symbol_node          = NEW_URI(LILV_NS_LV2  "symbol");
+	world->pset_value_node          = NEW_URI(NS_PSET "value");
 	world->rdf_a_node               = NEW_URI(LILV_NS_RDF  "type");
 	world->rdf_value_node           = NEW_URI(LILV_NS_RDF  "value");
 	world->rdfs_class_node          = NEW_URI(LILV_NS_RDFS "Class");
@@ -79,7 +83,6 @@ lilv_world_new(void)
 	world->xsd_integer_node         = NEW_URI(LILV_NS_XSD  "integer");
 
 	world->doap_name_val           = NEW_URI_VAL(LILV_NS_DOAP "name");
-	world->lv2_applies_to_val      = NEW_URI_VAL(LILV_NS_LV2  "appliesTo");
 	world->lv2_extensionData_val   = NEW_URI_VAL(LILV_NS_LV2  "extensionData");
 	world->lv2_name_val            = NEW_URI_VAL(LILV_NS_LV2  "name");
 	world->lv2_optionalFeature_val = NEW_URI_VAL(LILV_NS_LV2  "optionalFeature");
@@ -113,6 +116,7 @@ lilv_world_free(LilvWorld* world)
 
 	sord_node_free(world->world, world->dc_replaces_node);
 	sord_node_free(world->world, world->dyn_manifest_node);
+	sord_node_free(world->world, world->lv2_appliesTo_node);
 	sord_node_free(world->world, world->lv2_binary_node);
 	sord_node_free(world->world, world->lv2_default_node);
 	sord_node_free(world->world, world->lv2_index_node);
@@ -124,6 +128,7 @@ lilv_world_free(LilvWorld* world)
 	sord_node_free(world->world, world->lv2_reportslatency_node);
 	sord_node_free(world->world, world->lv2_specification_node);
 	sord_node_free(world->world, world->lv2_symbol_node);
+	sord_node_free(world->world, world->pset_value_node);
 	sord_node_free(world->world, world->rdf_a_node);
 	sord_node_free(world->world, world->rdf_value_node);
 	sord_node_free(world->world, world->rdfs_class_node);
@@ -135,7 +140,6 @@ lilv_world_free(LilvWorld* world)
 	sord_node_free(world->world, world->xsd_double_node);
 	sord_node_free(world->world, world->xsd_integer_node);
 	lilv_node_free(world->doap_name_val);
-	lilv_node_free(world->lv2_applies_to_val);
 	lilv_node_free(world->lv2_extensionData_val);
 	lilv_node_free(world->lv2_name_val);
 	lilv_node_free(world->lv2_optionalFeature_val);
@@ -585,7 +589,7 @@ expand(const char* path)
 	wordexp_t p;
 	if (wordexp(path, &p, 0)) {
 		LILV_ERRORF("Error expanding path `%s'\n", path);
-		return lilv_strdup (path);
+		return lilv_strdup(path);
 	}
 	if (p.we_wordc == 0) {
 		/* Literal directory path (e.g. no variables or ~) */
diff --git a/src/zix/tree.c b/src/zix/tree.c
index 1be9227..1189230 100644
--- a/src/zix/tree.c
+++ b/src/zix/tree.c
@@ -461,7 +461,7 @@ ZIX_API
 void*
 zix_tree_get(ZixTreeIter* ti)
 {
-	return ti->data;
+	return ti ? ti->data : NULL;
 }
 
 ZIX_API