hostplugins/lv2/lv2_state.h

/*
  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.h>

#ifdef __cplusplus
extern "C" {
#endif

#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state"

#define LV2_STATE_INTERFACE_URI LV2_STATE_URI "#Interface"
#define LV2_STATE_PATH_URI      LV2_STATE_URI "#Path"
#define LV2_STATE_MAP_PATH_URI  LV2_STATE_URI "#pathMap"
#define LV2_STATE_MAKE_PATH_URI LV2_STATE_URI "#newPath"

typedef void* LV2_State_Handle;
typedef void* LV2_State_Map_Path_Handle;
typedef void* LV2_State_Make_Path_Handle;

/**
   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 handle Must be the handle 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)(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 (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)(LV2_State_Handle handle,
                                                   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 handle 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 handle 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.
           @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 (possibly much later, in a different process, on
           a completely different machine, etc.)

           The @c handle 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,
                     LV2_State_Handle           handle,
                     uint32_t                   flags,
                     const LV2_Feature *const * features);


        /**
           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 handle 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 handle parameter.
           @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 @c handle 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,
                        LV2_State_Handle            handle,
                        uint32_t                    flags,
                        const LV2_Feature *const *  features);

} LV2_State_Interface;

/**
   Feature data for state:pathMap (LV2_STATE_MAP_PATH_URI).
*/
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 @a 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 files in plugin state.  The returned value is an abstract path which
           MAY not be an actual file system path; @ref absolute_path MUST be used
           to map it to an actual path in order to use the file.

           Hosts MAY map paths in any way (e.g. by creating symbolic links within
           the plugin's state directory or storing a list of referenced files
           elsewhere).  Plugins MUST NOT make any assumptions about abstract paths
           except that they can be mapped back to an absolute path using @ref
           absolute_path.

           This function may only be called within the context of
           LV2_State_Interface.save() or LV2_State_Interface.restore().  The caller
           is responsible for freeing the returned value.
        */
        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 @a handle member of this struct.
           @param abstract_path An abstract path (e.g. a path from plugin state).
           @return An absolute file system path.

           Since abstract paths are not necessarily actual file paths (or at least
           not necessarily absolute paths), this function MUST be used in order to
           actually open or otherwise use the file referred to by an abstract path.

           This function may only be called within the context of
           LV2_State_Interface.save() or LV2_State_Interface.restore().  The caller
           is responsible for freeing the returned value.
        */
        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_MAKE_PATH_URI).
*/
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 @a handle member of this struct.
           @param path The path of the new file relative to 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 */
1	capela	2292	/*
2			Copyright 2010-2011 David Robillard <http://drobilla.net>
3			Copyright 2010 Leonard Ritter <paniq@paniq.org>
4
5			Permission to use, copy, modify, and/or distribute this software for any
6			purpose with or without fee is hereby granted, provided that the above
7			copyright notice and this permission notice appear in all copies.
8
9			THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10			WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11			MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12			ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13			WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14			ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15			OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16			*/
17
18			/**
19			@file
20			C API for the LV2 State extension <http://lv2plug.in/ns/ext/state>.
21			*/
22
23			#ifndef LV2_STATE_H
24			#define LV2_STATE_H
25
26			#include <stdbool.h>
27			#include <stddef.h>
28			#include <stdint.h>
29
30	schoenebeck	2304	#include <lv2.h>
31	capela	2292
32			#ifdef __cplusplus
33			extern "C" {
34			#endif
35
36			#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state"
37
38			#define LV2_STATE_INTERFACE_URI LV2_STATE_URI "#Interface"
39			#define LV2_STATE_PATH_URI LV2_STATE_URI "#Path"
40			#define LV2_STATE_MAP_PATH_URI LV2_STATE_URI "#pathMap"
41			#define LV2_STATE_MAKE_PATH_URI LV2_STATE_URI "#newPath"
42
43			typedef void* LV2_State_Handle;
44			typedef void* LV2_State_Map_Path_Handle;
45			typedef void* LV2_State_Make_Path_Handle;
46
47			/**
48			Flags describing value characteristics.
49
50			These flags are used along with the value's type URI to determine how to
51			(de-)serialise the value data, or whether it is even possible to do so.
52			*/
53			typedef enum {
54
55			/**
56			Plain Old Data.
57
58			Values with this flag contain no references to non-stateent or
59			non-global resources (e.g. pointers, handles, local paths, etc.). It is
60			safe to copy POD values with a simple memcpy and store them for use at
61			any time in the future on a machine with a compatible architecture
62			(e.g. the same endianness and alignment).
63
64			Implementations MUST NOT attempt to copy or serialise a non-POD value if
65			they do not understand its type (and thus know how to correctly do so).
66			*/
67			LV2_STATE_IS_POD = 1,
68
69			/**
70			Portable (architecture independent) data.
71
72			Values with this flag are in a format that is usable on any
73			architecture, i.e. if the value is saved on one machine it can safely be
74			restored on another machine regardless of endianness, alignment, etc.
75			*/
76			LV2_STATE_IS_PORTABLE = 1 << 1,
77
78			/**
79			Native data.
80
81			This flag is used by the host to indicate that the saved data is only
82			going to be used locally in the currently running process (e.g. for
83			instance duplication or snapshots), so the plugin should use the most
84			efficient representation possible and not worry about serialisation
85			and portability.
86			*/
87			LV2_STATE_IS_NATIVE = 1 << 2
88
89			} LV2_State_Flags;
90
91			/**
92			A host-provided function to store a property.
93			@param handle Must be the handle passed to LV2_State_Interface.save().
94			@param key The key (predicate) to store @c value under (URI mapped integer).
95			@param value Pointer to the value (object) to be stored.
96			@param size The size of the data at @c value in bytes.
97			@param type The type of @c value (URI).
98			@param flags LV2_State_Flags for @c value.
99			@return 0 on success, otherwise a non-zero error code.
100
101			The host passes a callback of this type to LV2_State_Interface.save(). This callback
102			is called repeatedly by the plugin within LV2_State_Interface.save() to store all
103			the statements that describe its current state.
104
105			The host MAY fail to store a property if the type is not understood and is
106			not LV2_STATE_IS_POD and/or LV2_STATE_IS_PORTABLE. Implementations are
107			encouraged to use POD and portable values (e.g. string literals) wherever
108			possible, and use common types (e.g. types from
109			http://lv2plug.in/ns/ext/atom) regardless, since hosts are likely to already
110			contain the necessary implementation.
111
112			Note that @c size MUST be > 0, and @c value MUST point to a valid region of
113			memory @c size bytes long (this is required to make restore unambiguous).
114
115			The plugin MUST NOT attempt to use this function outside of the
116			LV2_State_Interface.restore() context.
117			*/
118			typedef int (*LV2_State_Store_Function)(LV2_State_Handle handle,
119			uint32_t key,
120			const void* value,
121			size_t size,
122			uint32_t type,
123			uint32_t flags);
124
125			/**
126			A host-provided function to retrieve a property.
127			@param handle Must be the handle passed to
128			LV2_State_Interface.restore().
129			@param key The key (predicate) of the property to retrieve (URI).
130			@param size (Output) If non-NULL, set to the size of the restored value.
131			@param type (Output) If non-NULL, set to the type of the restored value.
132			@param flags (Output) If non-NULL, set to the LV2_State_Flags for
133			the returned value.
134			@return A pointer to the restored value (object), or NULL if no value
135			has been stored under @c key.
136
137			A callback of this type is passed by the host to
138			LV2_State_Interface.restore(). This callback is called repeatedly by the
139			plugin within LV2_State_Interface.restore() to retrieve any properties it
140			requires to restore its state.
141
142			The returned value MUST remain valid until LV2_State_Interface.restore()
143			returns.
144
145			The plugin MUST NOT attempt to use this function, or any value returned from
146			it, outside of the LV2_State_Interface.restore() context. Returned values
147			MAY be copied for later use if necessary, assuming the plugin knows how to
148			do so correctly (e.g. the value is POD, or the plugin understands the type).
149			*/
150			typedef const void* (*LV2_State_Retrieve_Function)(LV2_State_Handle handle,
151			uint32_t key,
152			size_t* size,
153			uint32_t* type,
154			uint32_t* flags);
155
156			/**
157			State Extension Data.
158
159			When the plugin's extension_data is called with argument LV2_STATE_URI,
160			the plugin MUST return an LV2_State structure, which remains valid for the
161			lifetime of the plugin.
162
163			The host can use the contained function pointers to save and restore the
164			state of a plugin instance at any time (provided the threading restrictions
165			for the given function are met).
166
167			The typical use case is to save the plugin's state when a project is saved,
168			and to restore the state when a project has been loaded. Other uses are
169			possible (e.g. cloning plugin instances or taking a snapshot of plugin
170			state).
171
172			Stored data is only guaranteed to be compatible between instances of plugins
173			with the same URI (i.e. if a change to a plugin would cause a fatal error
174			when restoring state saved by a previous version of that plugin, the plugin
175			URI MUST change just as it must when ports change incompatibly). Plugin
176			authors should consider this possibility, and always store sensible data
177			with meaningful types to avoid such compatibility issues in the future.
178			*/
179			typedef struct _LV2_State_Interface {
180
181			/**
182			Save plugin state using a host-provided @c store callback.
183
184			@param instance The instance handle of the plugin.
185			@param store The host-provided store callback.
186			@param handle An opaque pointer to host data, e.g. the map or
187			file where the values are to be stored. If @c store is called, this MUST
188			be passed as its handle parameter.
189			@param flags Flags describing desires properties of this save. The
190			plugin SHOULD use these values to determine the most appropriate and/or
191			efficient serialisation, but is not required to do so.
192			@param features Extensible parameter for passing any additional
193			features to be used for this save.
194
195			The plugin is expected to store everything necessary to completely
196			restore its state later (possibly much later, in a different process, on
197			a completely different machine, etc.)
198
199			The @c handle pointer and @c store function MUST NOT be used
200			beyond the scope of save().
201
202			This function has its own special threading class: it may not be called
203			concurrently with any "Instantiation" function, but it may be called
204			concurrently with functions in any other class, unless the definition of
205			that class prohibits it (e.g. it may not be called concurrently with a
206			"Discovery" function, but it may be called concurrently with an "Audio"
207			function. The plugin is responsible for any locking or lock-free
208			techniques necessary to make this possible.
209
210			Note that in the simple case where state is only modified by restore(),
211			there are no synchronization issues since save() is never called
212			concurrently with restore() (though run() may read it during a save).
213
214			Plugins that dynamically modify state while running, however, must take
215			care to do so in such a way that a concurrent call to save() will save a
216			consistent representation of plugin state for a single instant in time.
217			*/
218			void (*save)(LV2_Handle instance,
219			LV2_State_Store_Function store,
220			LV2_State_Handle handle,
221			uint32_t flags,
222			const LV2_Feature const features);
223
224
225			/**
226			Restore plugin state using a host-provided @c retrieve callback.
227
228			@param instance The instance handle of the plugin.
229			@param retrieve The host-provided retrieve callback.
230			@param handle An opaque pointer to host data, e.g. the map or
231			file from which the values are to be restored. If @c retrieve is
232			called, this MUST be passed as its handle parameter.
233			@param flags Currently unused.
234			@param features Extensible parameter for passing any additional
235			features to be used for this restore.
236
237			The plugin MAY assume a restored value was set by a previous call to
238			LV2_State_Interface.save() by a plugin with the same URI.
239
240			The plugin MUST gracefully fall back to a default value when a value can
241			not be retrieved. This allows the host to reset the plugin state with an
242			empty map.
243
244			The @c handle pointer and @c store function MUST NOT be used
245			beyond the scope of restore().
246
247			This function is in the "Instantiation" threading class as defined by
248			LV2. This means it MUST NOT be called concurrently with any other
249			function on the same plugin instance.
250			*/
251			void (*restore)(LV2_Handle instance,
252			LV2_State_Retrieve_Function retrieve,
253			LV2_State_Handle handle,
254			uint32_t flags,
255			const LV2_Feature const features);
256
257			} LV2_State_Interface;
258
259			/**
260			Feature data for state:pathMap (LV2_STATE_MAP_PATH_URI).
261			*/
262			typedef struct {
263
264			/**
265			Opaque host data.
266			*/
267			LV2_State_Map_Path_Handle handle;
268
269			/**
270			Map an absolute path to an abstract path for use in plugin state.
271			@param handle MUST be the @a handle member of this struct.
272			@param absolute_path The absolute path of a file.
273			@return An abstract path suitable for use in plugin state.
274
275			The plugin MUST use this function to map any paths that will be stored
276			in files in plugin state. The returned value is an abstract path which
277			MAY not be an actual file system path; @ref absolute_path MUST be used
278			to map it to an actual path in order to use the file.
279
280			Hosts MAY map paths in any way (e.g. by creating symbolic links within
281			the plugin's state directory or storing a list of referenced files
282			elsewhere). Plugins MUST NOT make any assumptions about abstract paths
283			except that they can be mapped back to an absolute path using @ref
284			absolute_path.
285
286			This function may only be called within the context of
287			LV2_State_Interface.save() or LV2_State_Interface.restore(). The caller
288			is responsible for freeing the returned value.
289			*/
290			char* (*abstract_path)(LV2_State_Map_Path_Handle handle,
291			const char* absolute_path);
292
293			/**
294			Map an abstract path from plugin state to an absolute path.
295			@param handle MUST be the @a handle member of this struct.
296			@param abstract_path An abstract path (e.g. a path from plugin state).
297			@return An absolute file system path.
298
299			Since abstract paths are not necessarily actual file paths (or at least
300			not necessarily absolute paths), this function MUST be used in order to
301			actually open or otherwise use the file referred to by an abstract path.
302
303			This function may only be called within the context of
304			LV2_State_Interface.save() or LV2_State_Interface.restore(). The caller
305			is responsible for freeing the returned value.
306			*/
307			char* (*absolute_path)(LV2_State_Map_Path_Handle handle,
308			const char* abstract_path);
309
310			} LV2_State_Map_Path;
311
312			/**
313			Feature data for state:makePath (@ref LV2_STATE_MAKE_PATH_URI).
314			*/
315			typedef struct {
316
317			/**
318			Opaque host data.
319			*/
320			LV2_State_Make_Path_Handle handle;
321
322			/**
323			Return a path the plugin may use to create a new file.
324			@param handle MUST be the @a handle member of this struct.
325			@param path The path of the new file relative to a namespace unique
326			to this plugin instance.
327			@return The absolute path to use for the new file.
328
329			This function can be used by plugins to create files and directories,
330			either at state saving time (if this feature is passed to
331			LV2_State_Interface.save()) or any time (if this feature is passed to
332			LV2_Descriptor.instantiate()).
333
334			The host must do whatever is necessary for the plugin to be able to
335			create a file at the returned path (e.g. using fopen), including
336			creating any leading directories.
337
338			If this function is passed to LV2_Descriptor.instantiate(), it may be
339			called from any non-realtime context. If it is passed to
340			LV2_State_Interface.save(), it may only be called within the dynamic
341			scope of that function call.
342
343			The caller is responsible for freeing the returned value with free().
344			*/
345			char* (*path)(LV2_State_Make_Path_Handle handle,
346			const char* path);
347
348			} LV2_State_Make_Path;
349
350			#ifdef __cplusplus
351			} /* extern "C" */
352			#endif
353
354			#endif /* LV2_STATE_H */