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>

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