hostplugins/lv2/lv2_state.h

/*
  Copyright 2010-2012 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 state.h
   C API for the LV2 State extension <http://lv2plug.in/ns/ext/state>.
*/

#ifndef LV2_STATE_H
#define LV2_STATE_H

#include <stddef.h>
#include <stdint.h>

// LinuxSampler modification: use lv2.h instead of
// lv2/lv2plug.in/ns/lv2core/lv2.h, to support older lv2core packages
#include <lv2.h>

#define LV2_STATE_URI    "http://lv2plug.in/ns/ext/state"
#define LV2_STATE_PREFIX LV2_STATE_URI "#"

#define LV2_STATE__State     LV2_STATE_PREFIX "State"
#define LV2_STATE__interface LV2_STATE_PREFIX "interface"
#define LV2_STATE__makePath  LV2_STATE_PREFIX "makePath"
#define LV2_STATE__mapPath   LV2_STATE_PREFIX "mapPath"
#define LV2_STATE__state     LV2_STATE_PREFIX "state"

#ifdef __cplusplus
extern "C" {
#else
#    include <stdbool.h>
#endif

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 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_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 @p value under (URID).
   @param value Pointer to the value to be stored.
   @param size The size of @p value in bytes.
   @param type The type of @p value (URID).
   @param flags LV2_State_Flags for @p 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 @p size MUST be > 0, and @p value MUST point to a valid region of
   memory @p 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 @p 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 @p 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 @p 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 @p handle pointer and @p 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 @p 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 @p 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 @p handle pointer and @p 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 (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 @p 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; @ref 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 @ref 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 @p 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 @p 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 */
1	capela	2292	/*
2	capela	2340	Copyright 2010-2012 David Robillard <http://drobilla.net>
3	capela	2292	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	capela	2340	@file state.h
20	capela	2292	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 <stddef.h>
27			#include <stdint.h>
28
29	persson	2343	// LinuxSampler modification: use lv2.h instead of
30			// lv2/lv2plug.in/ns/lv2core/lv2.h, to support older lv2core packages
31			#include <lv2.h>
32	capela	2292
33	capela	2340	#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state"
34			#define LV2_STATE_PREFIX LV2_STATE_URI "#"
35
36			#define LV2_STATE__State LV2_STATE_PREFIX "State"
37			#define LV2_STATE__interface LV2_STATE_PREFIX "interface"
38			#define LV2_STATE__makePath LV2_STATE_PREFIX "makePath"
39			#define LV2_STATE__mapPath LV2_STATE_PREFIX "mapPath"
40			#define LV2_STATE__state LV2_STATE_PREFIX "state"
41
42	capela	2292	#ifdef __cplusplus
43			extern "C" {
44	capela	2340	#else
45			# include <stdbool.h>
46	capela	2292	#endif
47
48			typedef void* LV2_State_Handle;
49			typedef void* LV2_State_Map_Path_Handle;
50			typedef void* LV2_State_Make_Path_Handle;
51
52			/**
53			Flags describing value characteristics.
54
55			These flags are used along with the value's type URI to determine how to
56			(de-)serialise the value data, or whether it is even possible to do so.
57			*/
58			typedef enum {
59
60			/**
61			Plain Old Data.
62
63	capela	2340	Values with this flag contain no pointers or references to other areas
64			of memory. It is safe to copy POD values with a simple memcpy and store
65			them for the duration of the process. A POD value is not necessarily
66			safe to trasmit between processes or machines (e.g. filenames are POD),
67			see LV2_STATE_IS_PORTABLE for details.
68	capela	2292
69			Implementations MUST NOT attempt to copy or serialise a non-POD value if
70			they do not understand its type (and thus know how to correctly do so).
71			*/
72			LV2_STATE_IS_POD = 1,
73
74			/**
75			Portable (architecture independent) data.
76
77			Values with this flag are in a format that is usable on any
78	capela	2340	architecture. A portable value saved on one machine can be restored on
79			another machine regardless of architecture. The format of portable
80			values MUST NOT depend on architecture-specific properties like
81			endianness or alignment. Portable values MUST NOT contain filenames.
82	capela	2292	*/
83			LV2_STATE_IS_PORTABLE = 1 << 1,
84
85			/**
86			Native data.
87
88			This flag is used by the host to indicate that the saved data is only
89			going to be used locally in the currently running process (e.g. for
90			instance duplication or snapshots), so the plugin should use the most
91			efficient representation possible and not worry about serialisation
92			and portability.
93			*/
94			LV2_STATE_IS_NATIVE = 1 << 2
95
96			} LV2_State_Flags;
97
98	capela	2340	/** A status code for state functions. */
99			typedef enum {
100			LV2_STATE_SUCCESS = 0, /*< Completed successfully. /
101			LV2_STATE_ERR_UNKNOWN = 1, /*< Unknown error. /
102			LV2_STATE_ERR_BAD_TYPE = 2, /*< Failed due to unsupported type. /
103			LV2_STATE_ERR_BAD_FLAGS = 3, /*< Failed due to unsupported flags. /
104			LV2_STATE_ERR_NO_FEATURE = 4, /*< Failed due to missing features. /
105			LV2_STATE_ERR_NO_PROPERTY = 5 /*< Failed due to missing property. /
106			} LV2_State_Status;
107
108	capela	2292	/**
109			A host-provided function to store a property.
110			@param handle Must be the handle passed to LV2_State_Interface.save().
111	capela	2340	@param key The key to store @p value under (URID).
112			@param value Pointer to the value to be stored.
113			@param size The size of @p value in bytes.
114			@param type The type of @p value (URID).
115			@param flags LV2_State_Flags for @p value.
116	capela	2292	@return 0 on success, otherwise a non-zero error code.
117
118	capela	2340	The host passes a callback of this type to LV2_State_Interface.save(). This
119			callback is called repeatedly by the plugin to store all the properties that
120			describe its current state.
121	capela	2292
122	capela	2340	DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY. Best is to use keys from
123			existing vocabularies. If nothing appropriate is available, use http URIs
124			that point to somewhere you can host documents so documentation can be made
125			resolvable (e.g. a child of the plugin or project URI). If this is not
126			possible, invent a URN scheme, e.g. urn:myproj:whatever. The plugin MUST
127			NOT pass an invalid URI key.
128	capela	2292
129	capela	2340	The host MAY fail to store a property for whatever reason, but SHOULD
130			store any property that is LV2_STATE_IS_POD and LV2_STATE_IS_PORTABLE.
131			Implementations SHOULD use the types from the LV2 Atom extension
132			(http://lv2plug.in/ns/ext/atom) wherever possible. The plugin SHOULD
133			attempt to fall-back and avoid the error if possible.
134	capela	2292
135	capela	2340	Note that @p size MUST be > 0, and @p value MUST point to a valid region of
136			memory @p size bytes long (this is required to make restore unambiguous).
137
138	capela	2292	The plugin MUST NOT attempt to use this function outside of the
139			LV2_State_Interface.restore() context.
140			*/
141	capela	2340	typedef LV2_State_Status (*LV2_State_Store_Function)(
142			LV2_State_Handle handle,
143			uint32_t key,
144			const void* value,
145			size_t size,
146			uint32_t type,
147			uint32_t flags);
148	capela	2292
149			/**
150			A host-provided function to retrieve a property.
151	capela	2340	@param handle Must be the handle passed to LV2_State_Interface.restore().
152			@param key The key of the property to retrieve (URID).
153	capela	2292	@param size (Output) If non-NULL, set to the size of the restored value.
154			@param type (Output) If non-NULL, set to the type of the restored value.
155	capela	2340	@param flags (Output) If non-NULL, set to the flags for the restored value.
156	capela	2292	@return A pointer to the restored value (object), or NULL if no value
157	capela	2340	has been stored under @p key.
158	capela	2292
159			A callback of this type is passed by the host to
160	capela	2340	LV2_State_Interface.restore(). This callback is called repeatedly by the
161			plugin to retrieve any properties it requires to restore its state.
162	capela	2292
163			The returned value MUST remain valid until LV2_State_Interface.restore()
164	capela	2340	returns. The plugin MUST NOT attempt to use this function, or any value
165			returned from it, outside of the LV2_State_Interface.restore() context.
166	capela	2292	*/
167	capela	2340	typedef const void* (*LV2_State_Retrieve_Function)(
168			LV2_State_Handle handle,
169			uint32_t key,
170			size_t* size,
171			uint32_t* type,
172			uint32_t* flags);
173	capela	2292
174			/**
175	capela	2340	LV2 Plugin State Interface.
176	capela	2292
177	capela	2340	When the plugin's extension_data is called with argument
178			LV2_STATE__interface, the plugin MUST return an LV2_State_Interface
179			structure, which remains valid for the lifetime of the plugin.
180	capela	2292
181			The host can use the contained function pointers to save and restore the
182	capela	2340	state of a plugin instance at any time, provided the threading restrictions
183			of the functions are met.
184	capela	2292
185			Stored data is only guaranteed to be compatible between instances of plugins
186			with the same URI (i.e. if a change to a plugin would cause a fatal error
187			when restoring state saved by a previous version of that plugin, the plugin
188	capela	2340	URI MUST change just as it must when ports change incompatibly). Plugin
189	capela	2292	authors should consider this possibility, and always store sensible data
190	capela	2340	with meaningful types to avoid such problems in the future.
191	capela	2292	*/
192			typedef struct _LV2_State_Interface {
193
194			/**
195	capela	2340	Save plugin state using a host-provided @p store callback.
196	capela	2292
197			@param instance The instance handle of the plugin.
198			@param store The host-provided store callback.
199	capela	2340	@param handle An opaque pointer to host data which MUST be passed as the
200			handle parameter to @p store if it is called.
201			@param flags Flags describing desired properties of this save. These
202			flags may be used to determine the most appropriate values to store.
203	capela	2292	@param features Extensible parameter for passing any additional
204			features to be used for this save.
205
206			The plugin is expected to store everything necessary to completely
207	capela	2340	restore its state later. Plugins SHOULD store simple POD data whenever
208			possible, and consider the possibility of state being restored much
209			later on a different machine.
210	capela	2292
211	capela	2340	The @p handle pointer and @p store function MUST NOT be used
212	capela	2292	beyond the scope of save().
213
214			This function has its own special threading class: it may not be called
215			concurrently with any "Instantiation" function, but it may be called
216			concurrently with functions in any other class, unless the definition of
217			that class prohibits it (e.g. it may not be called concurrently with a
218			"Discovery" function, but it may be called concurrently with an "Audio"
219	capela	2340	function. The plugin is responsible for any locking or lock-free
220	capela	2292	techniques necessary to make this possible.
221
222			Note that in the simple case where state is only modified by restore(),
223			there are no synchronization issues since save() is never called
224			concurrently with restore() (though run() may read it during a save).
225
226			Plugins that dynamically modify state while running, however, must take
227			care to do so in such a way that a concurrent call to save() will save a
228			consistent representation of plugin state for a single instant in time.
229			*/
230	capela	2340	LV2_State_Status (*save)(LV2_Handle instance,
231			LV2_State_Store_Function store,
232			LV2_State_Handle handle,
233			uint32_t flags,
234			const LV2_Feature const features);
235	capela	2292
236			/**
237	capela	2340	Restore plugin state using a host-provided @p retrieve callback.
238	capela	2292
239			@param instance The instance handle of the plugin.
240			@param retrieve The host-provided retrieve callback.
241	capela	2340	@param handle An opaque pointer to host data which MUST be passed as the
242			handle parameter to @p retrieve if it is called.
243	capela	2292	@param flags Currently unused.
244			@param features Extensible parameter for passing any additional
245			features to be used for this restore.
246
247			The plugin MAY assume a restored value was set by a previous call to
248			LV2_State_Interface.save() by a plugin with the same URI.
249
250			The plugin MUST gracefully fall back to a default value when a value can
251	capela	2340	not be retrieved. This allows the host to reset the plugin state with
252			an empty map.
253	capela	2292
254	capela	2340	The @p handle pointer and @p store function MUST NOT be used
255	capela	2292	beyond the scope of restore().
256
257			This function is in the "Instantiation" threading class as defined by
258			LV2. This means it MUST NOT be called concurrently with any other
259			function on the same plugin instance.
260			*/
261	capela	2340	LV2_State_Status (*restore)(LV2_Handle instance,
262			LV2_State_Retrieve_Function retrieve,
263			LV2_State_Handle handle,
264			uint32_t flags,
265			const LV2_Feature const features);
266	capela	2292
267			} LV2_State_Interface;
268
269			/**
270	capela	2340	Feature data for state:mapPath (LV2_STATE__mapPath).
271	capela	2292	*/
272			typedef struct {
273
274			/**
275			Opaque host data.
276			*/
277			LV2_State_Map_Path_Handle handle;
278
279			/**
280			Map an absolute path to an abstract path for use in plugin state.
281	capela	2340	@param handle MUST be the @p handle member of this struct.
282	capela	2292	@param absolute_path The absolute path of a file.
283			@return An abstract path suitable for use in plugin state.
284
285			The plugin MUST use this function to map any paths that will be stored
286	capela	2340	in plugin state. The returned value is an abstract path which MAY not
287			be an actual file system path; @ref absolute_path() MUST be used to map
288			it to an actual path in order to use the file.
289	capela	2292
290	capela	2340	Plugins MUST NOT make any assumptions about abstract paths except that
291			they can be mapped back to the absolute path of the "same" file (though
292			not necessarily the same original path) using @ref absolute_path().
293	capela	2292
294			This function may only be called within the context of
295	capela	2340	LV2_State_Interface methods. The caller is responsible for freeing the
296			returned value with free().
297	capela	2292	*/
298			char* (*abstract_path)(LV2_State_Map_Path_Handle handle,
299			const char* absolute_path);
300
301			/**
302			Map an abstract path from plugin state to an absolute path.
303	capela	2340	@param handle MUST be the @p handle member of this struct.
304	capela	2292	@param abstract_path An abstract path (e.g. a path from plugin state).
305			@return An absolute file system path.
306
307	capela	2340	The plugin MUST use this function in order to actually open or otherwise
308			use any paths loaded from plugin state.
309	capela	2292
310			This function may only be called within the context of
311	capela	2340	LV2_State_Interface methods. The caller is responsible for freeing the
312			returned value with free().
313	capela	2292	*/
314			char* (*absolute_path)(LV2_State_Map_Path_Handle handle,
315			const char* abstract_path);
316
317			} LV2_State_Map_Path;
318
319			/**
320	capela	2340	Feature data for state:makePath (@ref LV2_STATE__makePath).
321	capela	2292	*/
322			typedef struct {
323
324			/**
325			Opaque host data.
326			*/
327			LV2_State_Make_Path_Handle handle;
328
329			/**
330			Return a path the plugin may use to create a new file.
331	capela	2340	@param handle MUST be the @p handle member of this struct.
332			@param path The path of the new file within a namespace unique to this
333			plugin instance.
334	capela	2292	@return The absolute path to use for the new file.
335
336			This function can be used by plugins to create files and directories,
337			either at state saving time (if this feature is passed to
338			LV2_State_Interface.save()) or any time (if this feature is passed to
339			LV2_Descriptor.instantiate()).
340
341	capela	2340	The host MUST do whatever is necessary for the plugin to be able to
342	capela	2292	create a file at the returned path (e.g. using fopen), including
343			creating any leading directories.
344
345			If this function is passed to LV2_Descriptor.instantiate(), it may be
346			called from any non-realtime context. If it is passed to
347			LV2_State_Interface.save(), it may only be called within the dynamic
348			scope of that function call.
349
350			The caller is responsible for freeing the returned value with free().
351			*/
352			char* (*path)(LV2_State_Make_Path_Handle handle,
353			const char* path);
354
355			} LV2_State_Make_Path;
356
357			#ifdef __cplusplus
358			} /* extern "C" */
359			#endif
360
361			#endif /* LV2_STATE_H */