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