/[svn]/linuxsampler/trunk/src/hostplugins/lv2/lv2_state.h
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revision 2311 by persson, Sat Feb 11 11:08:09 2012 UTC revision 2340 by capela, Fri Mar 30 23:54:44 2012 UTC
# Line 1  Line 1 
1  /*  /*
2    Copyright 2010-2011 David Robillard <http://drobilla.net>    Copyright 2010-2012 David Robillard <http://drobilla.net>
3    Copyright 2010 Leonard Ritter <paniq@paniq.org>    Copyright 2010 Leonard Ritter <paniq@paniq.org>
4    
5    Permission to use, copy, modify, and/or distribute this software for any    Permission to use, copy, modify, and/or distribute this software for any
# Line 16  Line 16 
16  */  */
17    
18  /**  /**
19     @file     @file state.h
20     C API for the LV2 State extension <http://lv2plug.in/ns/ext/state>.     C API for the LV2 State extension <http://lv2plug.in/ns/ext/state>.
21  */  */
22    
23  #ifndef LV2_STATE_H  #ifndef LV2_STATE_H
24  #define LV2_STATE_H  #define LV2_STATE_H
25    
 #include <stdbool.h>  
26  #include <stddef.h>  #include <stddef.h>
27  #include <stdint.h>  #include <stdint.h>
28    
29  #include <lv2.h>  #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  #ifdef __cplusplus
41  extern "C" {  extern "C" {
42    #else
43    #    include <stdbool.h>
44  #endif  #endif
45    
 #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 "#mapPath"  
 #define LV2_STATE_MAKE_PATH_URI LV2_STATE_URI "#makePath"  
   
46  typedef void* LV2_State_Handle;  typedef void* LV2_State_Handle;
47  typedef void* LV2_State_Map_Path_Handle;  typedef void* LV2_State_Map_Path_Handle;
48  typedef void* LV2_State_Make_Path_Handle;  typedef void* LV2_State_Make_Path_Handle;
# Line 55  typedef enum { Line 58  typedef enum {
58          /**          /**
59             Plain Old Data.             Plain Old Data.
60    
61             Values with this flag contain no references to non-persistent or             Values with this flag contain no pointers or references to other areas
62             non-global resources (e.g. pointers, handles, local paths, etc.). It is             of memory.  It is safe to copy POD values with a simple memcpy and store
63             safe to copy POD values with a simple memcpy and store them for use at             them for the duration of the process.  A POD value is not necessarily
64             any time in the future on a machine with a compatible architecture             safe to trasmit between processes or machines (e.g. filenames are POD),
65             (e.g. the same endianness and alignment).             see LV2_STATE_IS_PORTABLE for details.
66    
67             Implementations MUST NOT attempt to copy or serialise a non-POD value if             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).             they do not understand its type (and thus know how to correctly do so).
# Line 70  typedef enum { Line 73  typedef enum {
73             Portable (architecture independent) data.             Portable (architecture independent) data.
74    
75             Values with this flag are in a format that is usable on any             Values with this flag are in a format that is usable on any
76             architecture, i.e. if the value is saved on one machine it can safely be             architecture.  A portable value saved on one machine can be restored on
77             restored on another machine regardless of endianness, alignment, etc.             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,          LV2_STATE_IS_PORTABLE = 1 << 1,
82    
# Line 88  typedef enum { Line 93  typedef enum {
93    
94  } LV2_State_Flags;  } 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.     A host-provided function to store a property.
108     @param handle Must be the handle passed to LV2_State_Interface.save().     @param handle Must be the handle passed to LV2_State_Interface.save().
109     @param key The key (predicate) to store @c value under (URI mapped integer).     @param key The key to store @p value under (URID).
110     @param value Pointer to the value (object) to be stored.     @param value Pointer to the value to be stored.
111     @param size The size of the data at @c value in bytes.     @param size The size of @p value in bytes.
112     @param type The type of @c value (URI).     @param type The type of @p value (URID).
113     @param flags LV2_State_Flags for @c value.     @param flags LV2_State_Flags for @p value.
114     @return 0 on success, otherwise a non-zero error code.     @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 callback     The host passes a callback of this type to LV2_State_Interface.save(). This
117     is called repeatedly by the plugin within LV2_State_Interface.save() to store all     callback is called repeatedly by the plugin to store all the properties that
118     the statements that describe its current state.     describe its current state.
119    
120     The host MAY fail to store a property if the type is not understood and is     DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY.  Best is to use keys from
121     not LV2_STATE_IS_POD and/or LV2_STATE_IS_PORTABLE. Implementations are     existing vocabularies.  If nothing appropriate is available, use http URIs
122     encouraged to use POD and portable values (e.g. string literals) wherever     that point to somewhere you can host documents so documentation can be made
123     possible, and use common types (e.g. types from     resolvable (e.g. a child of the plugin or project URI).  If this is not
124     http://lv2plug.in/ns/ext/atom) regardless, since hosts are likely to already     possible, invent a URN scheme, e.g. urn:myproj:whatever.  The plugin MUST
125     contain the necessary implementation.     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 @c size MUST be > 0, and @c value MUST point to a valid region of     Note that @p size MUST be > 0, and @p value MUST point to a valid region of
134     memory @c size bytes long (this is required to make restore unambiguous).     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     The plugin MUST NOT attempt to use this function outside of the
137     LV2_State_Interface.restore() context.     LV2_State_Interface.restore() context.
138  */  */
139  typedef int (*LV2_State_Store_Function)(LV2_State_Handle handle,  typedef LV2_State_Status (*LV2_State_Store_Function)(
140                                          uint32_t         key,          LV2_State_Handle handle,
141                                          const void*      value,          uint32_t         key,
142                                          size_t           size,          const void*      value,
143                                          uint32_t         type,          size_t           size,
144                                          uint32_t         flags);          uint32_t         type,
145            uint32_t         flags);
146    
147  /**  /**
148     A host-provided function to retrieve a property.     A host-provided function to retrieve a property.
149     @param handle Must be the handle passed to     @param handle Must be the handle passed to LV2_State_Interface.restore().
150     LV2_State_Interface.restore().     @param key The key of the property to retrieve (URID).
    @param key The key (predicate) of the property to retrieve (URI).  
151     @param size (Output) If non-NULL, set to the size of the restored value.     @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.     @param type (Output) If non-NULL, set to the type of the restored value.
153     @param flags (Output) If non-NULL, set to the LV2_State_Flags for     @param flags (Output) If non-NULL, set to the flags for the restored value.
    the returned value.  
154     @return A pointer to the restored value (object), or NULL if no value     @return A pointer to the restored value (object), or NULL if no value
155     has been stored under @c key.     has been stored under @p key.
156    
157     A callback of this type is passed by the host to     A callback of this type is passed by the host to
158     LV2_State_Interface.restore(). This callback is called repeatedly by the     LV2_State_Interface.restore().  This callback is called repeatedly by the
159     plugin within LV2_State_Interface.restore() to retrieve any properties it     plugin to retrieve any properties it requires to restore its state.
    requires to restore its state.  
160    
161     The returned value MUST remain valid until LV2_State_Interface.restore()     The returned value MUST remain valid until LV2_State_Interface.restore()
162     returns.     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.
    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).  
164  */  */
165  typedef const void* (*LV2_State_Retrieve_Function)(LV2_State_Handle handle,  typedef const void* (*LV2_State_Retrieve_Function)(
166                                                     uint32_t         key,          LV2_State_Handle handle,
167                                                     size_t*          size,          uint32_t         key,
168                                                     uint32_t*        type,          size_t*          size,
169                                                     uint32_t*        flags);          uint32_t*        type,
170            uint32_t*        flags);
171    
172  /**  /**
173     State Extension Data.     LV2 Plugin State Interface.
174    
175     When the plugin's extension_data is called with argument LV2_STATE_URI,     When the plugin's extension_data is called with argument
176     the plugin MUST return an LV2_State structure, which remains valid for the     LV2_STATE__interface, the plugin MUST return an LV2_State_Interface
177     lifetime of the plugin.     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     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     state of a plugin instance at any time, provided the threading restrictions
181     for the given function are met).     of the functions 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).  
182    
183     Stored data is only guaranteed to be compatible between instances of plugins     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     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     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     URI MUST change just as it must when ports change incompatibly).  Plugin
187     authors should consider this possibility, and always store sensible data     authors should consider this possibility, and always store sensible data
188     with meaningful types to avoid such compatibility issues in the future.     with meaningful types to avoid such problems in the future.
189  */  */
190  typedef struct _LV2_State_Interface {  typedef struct _LV2_State_Interface {
191    
192          /**          /**
193             Save plugin state using a host-provided @c store callback.             Save plugin state using a host-provided @p store callback.
194    
195             @param instance The instance handle of the plugin.             @param instance The instance handle of the plugin.
196             @param store The host-provided store callback.             @param store The host-provided store callback.
197             @param handle An opaque pointer to host data, e.g. the map or             @param handle An opaque pointer to host data which MUST be passed as the
198             file where the values are to be stored. If @c store is called, this MUST             handle parameter to @p store if it is called.
199             be passed as its handle parameter.             @param flags Flags describing desired properties of this save.  These
200             @param flags Flags describing desires properties of this save.  The             flags may be used to determine the most appropriate values to store.
            plugin SHOULD use these values to determine the most appropriate and/or  
            efficient serialisation, but is not required to do so.  
201             @param features Extensible parameter for passing any additional             @param features Extensible parameter for passing any additional
202             features to be used for this save.             features to be used for this save.
203    
204             The plugin is expected to store everything necessary to completely             The plugin is expected to store everything necessary to completely
205             restore its state later (possibly much later, in a different process, on             restore its state later.  Plugins SHOULD store simple POD data whenever
206             a completely different machine, etc.)             possible, and consider the possibility of state being restored much
207               later on a different machine.
208    
209             The @c handle pointer and @c store function MUST NOT be used             The @p handle pointer and @p store function MUST NOT be used
210             beyond the scope of save().             beyond the scope of save().
211    
212             This function has its own special threading class: it may not be called             This function has its own special threading class: it may not be called
# Line 204  typedef struct _LV2_State_Interface { Line 214  typedef struct _LV2_State_Interface {
214             concurrently with functions in any other class, unless the definition of             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             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"             "Discovery" function, but it may be called concurrently with an "Audio"
217             function. The plugin is responsible for any locking or lock-free             function.  The plugin is responsible for any locking or lock-free
218             techniques necessary to make this possible.             techniques necessary to make this possible.
219    
220             Note that in the simple case where state is only modified by restore(),             Note that in the simple case where state is only modified by restore(),
# Line 215  typedef struct _LV2_State_Interface { Line 225  typedef struct _LV2_State_Interface {
225             care to do so in such a way that a concurrent call to save() will save a             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.             consistent representation of plugin state for a single instant in time.
227          */          */
228          void (*save)(LV2_Handle                 instance,          LV2_State_Status (*save)(LV2_Handle                 instance,
229                       LV2_State_Store_Function   store,                                   LV2_State_Store_Function   store,
230                       LV2_State_Handle           handle,                                   LV2_State_Handle           handle,
231                       uint32_t                   flags,                                   uint32_t                   flags,
232                       const LV2_Feature *const * features);                                   const LV2_Feature *const * features);
233    
234          /**          /**
235             Restore plugin state using a host-provided @c retrieve callback.             Restore plugin state using a host-provided @p retrieve callback.
236    
237             @param instance The instance handle of the plugin.             @param instance The instance handle of the plugin.
238             @param retrieve The host-provided retrieve callback.             @param retrieve The host-provided retrieve callback.
239             @param handle An opaque pointer to host data, e.g. the map or             @param handle An opaque pointer to host data which MUST be passed as the
240             file from which the values are to be restored. If @c retrieve is             handle parameter to @p retrieve if it is called.
            called, this MUST be passed as its handle parameter.  
241             @param flags Currently unused.             @param flags Currently unused.
242             @param features Extensible parameter for passing any additional             @param features Extensible parameter for passing any additional
243             features to be used for this restore.             features to be used for this restore.
# Line 237  typedef struct _LV2_State_Interface { Line 246  typedef struct _LV2_State_Interface {
246             LV2_State_Interface.save() by a plugin with the same URI.             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             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 an             not be retrieved.  This allows the host to reset the plugin state with
250             empty map.             an empty map.
251    
252             The @c handle pointer and @c store function MUST NOT be used             The @p handle pointer and @p store function MUST NOT be used
253             beyond the scope of restore().             beyond the scope of restore().
254    
255             This function is in the "Instantiation" threading class as defined by             This function is in the "Instantiation" threading class as defined by
256             LV2. This means it MUST NOT be called concurrently with any other             LV2. This means it MUST NOT be called concurrently with any other
257             function on the same plugin instance.             function on the same plugin instance.
258          */          */
259          void (*restore)(LV2_Handle                  instance,          LV2_State_Status (*restore)(LV2_Handle                  instance,
260                          LV2_State_Retrieve_Function retrieve,                                      LV2_State_Retrieve_Function retrieve,
261                          LV2_State_Handle            handle,                                      LV2_State_Handle            handle,
262                          uint32_t                    flags,                                      uint32_t                    flags,
263                          const LV2_Feature *const *  features);                                      const LV2_Feature *const *  features);
264    
265  } LV2_State_Interface;  } LV2_State_Interface;
266    
267  /**  /**
268     Feature data for state:mapPath (LV2_STATE_MAP_PATH_URI).     Feature data for state:mapPath (LV2_STATE__mapPath).
269  */  */
270  typedef struct {  typedef struct {
271    
# Line 267  typedef struct { Line 276  typedef struct {
276    
277          /**          /**
278             Map an absolute path to an abstract path for use in plugin state.             Map an absolute path to an abstract path for use in plugin state.
279             @param handle MUST be the @a handle member of this struct.             @param handle MUST be the @p handle member of this struct.
280             @param absolute_path The absolute path of a file.             @param absolute_path The absolute path of a file.
281             @return An abstract path suitable for use in plugin state.             @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             The plugin MUST use this function to map any paths that will be stored
284             in files in plugin state.  The returned value is an abstract path which             in plugin state.  The returned value is an abstract path which MAY not
285             MAY not be an actual file system path; @ref absolute_path MUST be used             be an actual file system path; @ref absolute_path() MUST be used to map
286             to map it to an actual path in order to use the file.             it to an actual path in order to use the file.
287    
288             Hosts MAY map paths in any way (e.g. by creating symbolic links within             Plugins MUST NOT make any assumptions about abstract paths except that
289             the plugin's state directory or storing a list of referenced files             they can be mapped back to the absolute path of the "same" file (though
290             elsewhere).  Plugins MUST NOT make any assumptions about abstract paths             not necessarily the same original path) using @ref absolute_path().
            except that they can be mapped back to an absolute path using @ref  
            absolute_path.  
291    
292             This function may only be called within the context of             This function may only be called within the context of
293             LV2_State_Interface.save() or LV2_State_Interface.restore().  The caller             LV2_State_Interface methods.  The caller is responsible for freeing the
294             is responsible for freeing the returned value.             returned value with free().
295          */          */
296          char* (*abstract_path)(LV2_State_Map_Path_Handle handle,          char* (*abstract_path)(LV2_State_Map_Path_Handle handle,
297                                 const char*               absolute_path);                                 const char*               absolute_path);
298    
299          /**          /**
300             Map an abstract path from plugin state to an absolute path.             Map an abstract path from plugin state to an absolute path.
301             @param handle MUST be the @a handle member of this struct.             @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).             @param abstract_path An abstract path (e.g. a path from plugin state).
303             @return An absolute file system path.             @return An absolute file system path.
304    
305             Since abstract paths are not necessarily actual file paths (or at least             The plugin MUST use this function in order to actually open or otherwise
306             not necessarily absolute paths), this function MUST be used in order to             use any paths loaded from plugin state.
            actually open or otherwise use the file referred to by an abstract path.  
307    
308             This function may only be called within the context of             This function may only be called within the context of
309             LV2_State_Interface.save() or LV2_State_Interface.restore().  The caller             LV2_State_Interface methods.  The caller is responsible for freeing the
310             is responsible for freeing the returned value.             returned value with free().
311          */          */
312          char* (*absolute_path)(LV2_State_Map_Path_Handle handle,          char* (*absolute_path)(LV2_State_Map_Path_Handle handle,
313                                 const char*               abstract_path);                                 const char*               abstract_path);
# Line 309  typedef struct { Line 315  typedef struct {
315  } LV2_State_Map_Path;  } LV2_State_Map_Path;
316    
317  /**  /**
318     Feature data for state:makePath (@ref LV2_STATE_MAKE_PATH_URI).     Feature data for state:makePath (@ref LV2_STATE__makePath).
319  */  */
320  typedef struct {  typedef struct {
321    
# Line 320  typedef struct { Line 326  typedef struct {
326    
327          /**          /**
328             Return a path the plugin may use to create a new file.             Return a path the plugin may use to create a new file.
329             @param handle MUST be the @a handle member of this struct.             @param handle MUST be the @p handle member of this struct.
330             @param path The path of the new file relative to a namespace unique             @param path The path of the new file within a namespace unique to this
331             to this plugin instance.             plugin instance.
332             @return The absolute path to use for the new file.             @return The absolute path to use for the new file.
333    
334             This function can be used by plugins to create files and directories,             This function can be used by plugins to create files and directories,
# Line 330  typedef struct { Line 336  typedef struct {
336             LV2_State_Interface.save()) or any time (if this feature is passed to             LV2_State_Interface.save()) or any time (if this feature is passed to
337             LV2_Descriptor.instantiate()).             LV2_Descriptor.instantiate()).
338    
339             The host must do whatever is necessary for the plugin to be able to             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             create a file at the returned path (e.g. using fopen), including
341             creating any leading directories.             creating any leading directories.
342    
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