state.h (16452B)
1 /* 2 Copyright 2010-2016 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 @defgroup state State 20 @ingroup lv2 21 22 An interface for LV2 plugins to save and restore state, see 23 <http://lv2plug.in/ns/ext/state> for details. 24 25 @{ 26 */ 27 28 #ifndef LV2_STATE_H 29 #define LV2_STATE_H 30 31 #include "lv2.h" 32 33 #include <stdbool.h> 34 #include <stddef.h> 35 #include <stdint.h> 36 37 #define LV2_STATE_URI "http://lv2plug.in/ns/ext/state" ///< http://lv2plug.in/ns/ext/state 38 #define LV2_STATE_PREFIX LV2_STATE_URI "#" ///< http://lv2plug.in/ns/ext/state# 39 40 #define LV2_STATE__State LV2_STATE_PREFIX "State" ///< http://lv2plug.in/ns/ext/state#State 41 #define LV2_STATE__interface LV2_STATE_PREFIX "interface" ///< http://lv2plug.in/ns/ext/state#interface 42 #define LV2_STATE__loadDefaultState LV2_STATE_PREFIX "loadDefaultState" ///< http://lv2plug.in/ns/ext/state#loadDefaultState 43 #define LV2_STATE__freePath LV2_STATE_PREFIX "freePath" ///< http://lv2plug.in/ns/ext/state#freePath 44 #define LV2_STATE__makePath LV2_STATE_PREFIX "makePath" ///< http://lv2plug.in/ns/ext/state#makePath 45 #define LV2_STATE__mapPath LV2_STATE_PREFIX "mapPath" ///< http://lv2plug.in/ns/ext/state#mapPath 46 #define LV2_STATE__state LV2_STATE_PREFIX "state" ///< http://lv2plug.in/ns/ext/state#state 47 #define LV2_STATE__threadSafeRestore LV2_STATE_PREFIX "threadSafeRestore" ///< http://lv2plug.in/ns/ext/state#threadSafeRestore 48 #define LV2_STATE__StateChanged LV2_STATE_PREFIX "StateChanged" ///< http://lv2plug.in/ns/ext/state#StateChanged 49 50 #ifdef __cplusplus 51 extern "C" { 52 #endif 53 54 typedef void* LV2_State_Handle; ///< Opaque handle for state save/restore 55 typedef void* LV2_State_Free_Path_Handle; ///< Opaque handle for state:freePath feature 56 typedef void* LV2_State_Map_Path_Handle; ///< Opaque handle for state:mapPath feature 57 typedef void* LV2_State_Make_Path_Handle; ///< Opaque handle for state:makePath feature 58 59 /** 60 Flags describing value characteristics. 61 62 These flags are used along with the value's type URI to determine how to 63 (de-)serialise the value data, or whether it is even possible to do so. 64 */ 65 typedef enum { 66 /** 67 Plain Old Data. 68 69 Values with this flag contain no pointers or references to other areas 70 of memory. It is safe to copy POD values with a simple memcpy and store 71 them for the duration of the process. A POD value is not necessarily 72 safe to trasmit between processes or machines (for example, filenames 73 are POD), see LV2_STATE_IS_PORTABLE for details. 74 75 Implementations MUST NOT attempt to copy or serialise a non-POD value if 76 they do not understand its type (and thus know how to correctly do so). 77 */ 78 LV2_STATE_IS_POD = 1, 79 80 /** 81 Portable (architecture independent) data. 82 83 Values with this flag are in a format that is usable on any 84 architecture. A portable value saved on one machine can be restored on 85 another machine regardless of architecture. The format of portable 86 values MUST NOT depend on architecture-specific properties like 87 endianness or alignment. Portable values MUST NOT contain filenames. 88 */ 89 LV2_STATE_IS_PORTABLE = 1 << 1, 90 91 /** 92 Native data. 93 94 This flag is used by the host to indicate that the saved data is only 95 going to be used locally in the currently running process (for things 96 like instance duplication or snapshots), so the plugin should use the 97 most efficient representation possible and not worry about serialisation 98 and portability. 99 */ 100 LV2_STATE_IS_NATIVE = 1 << 2 101 } LV2_State_Flags; 102 103 /** A status code for state functions. */ 104 typedef enum { 105 LV2_STATE_SUCCESS = 0, /**< Completed successfully. */ 106 LV2_STATE_ERR_UNKNOWN = 1, /**< Unknown error. */ 107 LV2_STATE_ERR_BAD_TYPE = 2, /**< Failed due to unsupported type. */ 108 LV2_STATE_ERR_BAD_FLAGS = 3, /**< Failed due to unsupported flags. */ 109 LV2_STATE_ERR_NO_FEATURE = 4, /**< Failed due to missing features. */ 110 LV2_STATE_ERR_NO_PROPERTY = 5, /**< Failed due to missing property. */ 111 LV2_STATE_ERR_NO_SPACE = 6 /**< Failed due to insufficient space. */ 112 } LV2_State_Status; 113 114 /** 115 A host-provided function to store a property. 116 @param handle Must be the handle passed to LV2_State_Interface.save(). 117 @param key The key to store `value` under (URID). 118 @param value Pointer to the value to be stored. 119 @param size The size of `value` in bytes. 120 @param type The type of `value` (URID). 121 @param flags LV2_State_Flags for `value`. 122 @return 0 on success, otherwise a non-zero error code. 123 124 The host passes a callback of this type to LV2_State_Interface.save(). This 125 callback is called repeatedly by the plugin to store all the properties that 126 describe its current state. 127 128 DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY. Best is to use keys from 129 existing vocabularies. If nothing appropriate is available, use http URIs 130 that point to somewhere you can host documents so documentation can be made 131 resolvable (typically a child of the plugin or project URI). If this is not 132 possible, invent a URN scheme, e.g. urn:myproj:whatever. The plugin MUST 133 NOT pass an invalid URI key. 134 135 The host MAY fail to store a property for whatever reason, but SHOULD 136 store any property that is LV2_STATE_IS_POD and LV2_STATE_IS_PORTABLE. 137 Implementations SHOULD use the types from the LV2 Atom extension 138 (http://lv2plug.in/ns/ext/atom) wherever possible. The plugin SHOULD 139 attempt to fall-back and avoid the error if possible. 140 141 Note that `size` MUST be > 0, and `value` MUST point to a valid region of 142 memory `size` bytes long (this is required to make restore unambiguous). 143 144 The plugin MUST NOT attempt to use this function outside of the 145 LV2_State_Interface.restore() context. 146 */ 147 typedef LV2_State_Status (*LV2_State_Store_Function)( 148 LV2_State_Handle handle, 149 uint32_t key, 150 const void* value, 151 size_t size, 152 uint32_t type, 153 uint32_t flags); 154 155 /** 156 A host-provided function to retrieve a property. 157 @param handle Must be the handle passed to LV2_State_Interface.restore(). 158 @param key The key of the property to retrieve (URID). 159 @param size (Output) If non-NULL, set to the size of the restored value. 160 @param type (Output) If non-NULL, set to the type of the restored value. 161 @param flags (Output) If non-NULL, set to the flags for the restored value. 162 @return A pointer to the restored value (object), or NULL if no value 163 has been stored under `key`. 164 165 A callback of this type is passed by the host to 166 LV2_State_Interface.restore(). This callback is called repeatedly by the 167 plugin to retrieve any properties it requires to restore its state. 168 169 The returned value MUST remain valid until LV2_State_Interface.restore() 170 returns. The plugin MUST NOT attempt to use this function, or any value 171 returned from it, outside of the LV2_State_Interface.restore() context. 172 */ 173 typedef const void* (*LV2_State_Retrieve_Function)( 174 LV2_State_Handle handle, 175 uint32_t key, 176 size_t* size, 177 uint32_t* type, 178 uint32_t* flags); 179 180 /** 181 LV2 Plugin State Interface. 182 183 When the plugin's extension_data is called with argument 184 LV2_STATE__interface, the plugin MUST return an LV2_State_Interface 185 structure, which remains valid for the lifetime of the plugin. 186 187 The host can use the contained function pointers to save and restore the 188 state of a plugin instance at any time, provided the threading restrictions 189 of the functions are met. 190 191 Stored data is only guaranteed to be compatible between instances of plugins 192 with the same URI (i.e. if a change to a plugin would cause a fatal error 193 when restoring state saved by a previous version of that plugin, the plugin 194 URI MUST change just as it must when ports change incompatibly). Plugin 195 authors should consider this possibility, and always store sensible data 196 with meaningful types to avoid such problems in the future. 197 */ 198 typedef struct { 199 /** 200 Save plugin state using a host-provided `store` callback. 201 202 @param instance The instance handle of the plugin. 203 @param store The host-provided store callback. 204 @param handle An opaque pointer to host data which MUST be passed as the 205 handle parameter to `store` if it is called. 206 @param flags Flags describing desired properties of this save. These 207 flags may be used to determine the most appropriate values to store. 208 @param features Extensible parameter for passing any additional 209 features to be used for this save. 210 211 The plugin is expected to store everything necessary to completely 212 restore its state later. Plugins SHOULD store simple POD data whenever 213 possible, and consider the possibility of state being restored much 214 later on a different machine. 215 216 The `handle` pointer and `store` function MUST NOT be used 217 beyond the scope of save(). 218 219 This function has its own special threading class: it may not be called 220 concurrently with any "Instantiation" function, but it may be called 221 concurrently with functions in any other class, unless the definition of 222 that class prohibits it (for example, it may not be called concurrently 223 with a "Discovery" function, but it may be called concurrently with an 224 "Audio" function. The plugin is responsible for any locking or 225 lock-free techniques necessary to make this possible. 226 227 Note that in the simple case where state is only modified by restore(), 228 there are no synchronization issues since save() is never called 229 concurrently with restore() (though run() may read it during a save). 230 231 Plugins that dynamically modify state while running, however, must take 232 care to do so in such a way that a concurrent call to save() will save a 233 consistent representation of plugin state for a single instant in time. 234 */ 235 LV2_State_Status (*save)(LV2_Handle instance, 236 LV2_State_Store_Function store, 237 LV2_State_Handle handle, 238 uint32_t flags, 239 const LV2_Feature *const * features); 240 241 /** 242 Restore plugin state using a host-provided `retrieve` callback. 243 244 @param instance The instance handle of the plugin. 245 @param retrieve The host-provided retrieve callback. 246 @param handle An opaque pointer to host data which MUST be passed as the 247 handle parameter to `retrieve` if it is called. 248 @param flags Currently unused. 249 @param features Extensible parameter for passing any additional 250 features to be used for this restore. 251 252 The plugin MAY assume a restored value was set by a previous call to 253 LV2_State_Interface.save() by a plugin with the same URI. 254 255 The plugin MUST gracefully fall back to a default value when a value can 256 not be retrieved. This allows the host to reset the plugin state with 257 an empty map. 258 259 The `handle` pointer and `store` function MUST NOT be used 260 beyond the scope of restore(). 261 262 This function is in the "Instantiation" threading class as defined by 263 LV2. This means it MUST NOT be called concurrently with any other 264 function on the same plugin instance. 265 */ 266 LV2_State_Status (*restore)(LV2_Handle instance, 267 LV2_State_Retrieve_Function retrieve, 268 LV2_State_Handle handle, 269 uint32_t flags, 270 const LV2_Feature *const * features); 271 } LV2_State_Interface; 272 273 /** 274 Feature data for state:mapPath (@ref LV2_STATE__mapPath). 275 */ 276 typedef struct { 277 /** 278 Opaque host data. 279 */ 280 LV2_State_Map_Path_Handle handle; 281 282 /** 283 Map an absolute path to an abstract path for use in plugin state. 284 @param handle MUST be the `handle` member of this struct. 285 @param absolute_path The absolute path of a file. 286 @return An abstract path suitable for use in plugin state. 287 288 The plugin MUST use this function to map any paths that will be stored 289 in plugin state. The returned value is an abstract path which MAY not 290 be an actual file system path; absolute_path() MUST be used to map 291 it to an actual path in order to use the file. 292 293 Plugins MUST NOT make any assumptions about abstract paths except that 294 they can be mapped back to the absolute path of the "same" file (though 295 not necessarily the same original path) using absolute_path(). 296 297 This function may only be called within the context of 298 LV2_State_Interface methods. The caller must free the returned value 299 with LV2_State_Free_Path.free_path(). 300 */ 301 char* (*abstract_path)(LV2_State_Map_Path_Handle handle, 302 const char* absolute_path); 303 304 /** 305 Map an abstract path from plugin state to an absolute path. 306 @param handle MUST be the `handle` member of this struct. 307 @param abstract_path An abstract path (typically from plugin state). 308 @return An absolute file system path. 309 310 The plugin MUST use this function in order to actually open or otherwise 311 use any paths loaded from plugin state. 312 313 This function may only be called within the context of 314 LV2_State_Interface methods. The caller must free the returned value 315 with LV2_State_Free_Path.free_path(). 316 */ 317 char* (*absolute_path)(LV2_State_Map_Path_Handle handle, 318 const char* abstract_path); 319 } LV2_State_Map_Path; 320 321 /** 322 Feature data for state:makePath (@ref LV2_STATE__makePath). 323 */ 324 typedef struct { 325 /** 326 Opaque host data. 327 */ 328 LV2_State_Make_Path_Handle handle; 329 330 /** 331 Return a path the plugin may use to create a new file. 332 @param handle MUST be the `handle` member of this struct. 333 @param path The path of the new file within a namespace unique to this 334 plugin instance. 335 @return The absolute path to use for the new file. 336 337 This function can be used by plugins to create files and directories, 338 either at state saving time (if this feature is passed to 339 LV2_State_Interface.save()) or any time (if this feature is passed to 340 LV2_Descriptor.instantiate()). 341 342 The host MUST do whatever is necessary for the plugin to be able to 343 create a file at the returned path (for example, using fopen()), 344 including creating any leading directories. 345 346 If this function is passed to LV2_Descriptor.instantiate(), it may be 347 called from any non-realtime context. If it is passed to 348 LV2_State_Interface.save(), it may only be called within the dynamic 349 scope of that function call. 350 351 The caller must free the returned value with 352 LV2_State_Free_Path.free_path(). 353 */ 354 char* (*path)(LV2_State_Make_Path_Handle handle, 355 const char* path); 356 } LV2_State_Make_Path; 357 358 /** 359 Feature data for state:freePath (@ref LV2_STATE__freePath). 360 */ 361 typedef struct { 362 /** 363 Opaque host data. 364 */ 365 LV2_State_Free_Path_Handle handle; 366 367 /** 368 Free a path returned by a state feature. 369 370 @param handle MUST be the `handle` member of this struct. 371 @param path The path previously returned by a state feature. 372 373 This function can be used by plugins to free paths allocated by the host 374 and returned by state features (LV2_State_Map_Path.abstract_path(), 375 LV2_State_Map_Path.absolute_path(), and LV2_State_Make_Path.path()). 376 */ 377 void (*free_path)(LV2_State_Free_Path_Handle handle, 378 char* path); 379 } LV2_State_Free_Path; 380 381 #ifdef __cplusplus 382 } /* extern "C" */ 383 #endif 384 385 #endif /* LV2_STATE_H */ 386 387 /** 388 @} 389 */