1 /* 2 Copyright 2010-2016 David Robillard <http://drobilla.net> 3 Copyright 2010 Leonard Ritter <paniq@paniq.org> 4 Copyright 2018 Ethan Reker <http://cutthroughrecordings.com> 5 6 Permission to use, copy, modify, and/or distribute this software for any 7 purpose with or without fee is hereby granted, provided that the above 8 copyright notice and this permission notice appear in all copies. 9 10 THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 /** 20 @defgroup state State 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 module dplug.lv2.state; 28 29 version(LV2): 30 31 import core.stdc.stddef; 32 import core.stdc.stdint; 33 34 import dplug.lv2.lv2; 35 36 enum LV2_STATE_URI = "http://lv2plug.in/ns/ext/state"; ///< http://lv2plug.in/ns/ext/state 37 enum LV2_STATE_PREFIX = LV2_STATE_URI ~ "#"; ///< http://lv2plug.in/ns/ext/state# 38 39 enum LV2_STATE__State = LV2_STATE_PREFIX ~ "State"; ///< http://lv2plug.in/ns/ext/state#State 40 enum LV2_STATE__interface = LV2_STATE_PREFIX ~ "interface"; ///< http://lv2plug.in/ns/ext/state#interface 41 enum LV2_STATE__loadDefaultState = LV2_STATE_PREFIX ~ "loadDefaultState"; ///< http://lv2plug.in/ns/ext/state#loadDefaultState 42 enum LV2_STATE__makePath = LV2_STATE_PREFIX ~ "makePath"; ///< http://lv2plug.in/ns/ext/state#makePath 43 enum LV2_STATE__mapPath = LV2_STATE_PREFIX ~ "mapPath"; ///< http://lv2plug.in/ns/ext/state#mapPath 44 enum LV2_STATE__state = LV2_STATE_PREFIX ~ "state"; ///< http://lv2plug.in/ns/ext/state#state 45 enum LV2_STATE__threadSafeRestore = LV2_STATE_PREFIX ~ "threadSafeRestore"; ///< http://lv2plug.in/ns/ext/state#threadSafeRestore 46 47 extern(C) { 48 49 alias LV2_State_Handle = void*; ///< Opaque handle for state save/restore 50 alias LV2_State_Map_Path_Handle = void*; ///< Opaque handle for state:mapPath feature 51 alias LV2_State_Make_Path_Handle = void*; ///< Opaque handle for state:makePath feature 52 53 /** 54 Flags describing value characteristics. 55 56 These flags are used along with the value's type URI to determine how to 57 (de-)serialise the value data, or whether it is even possible to do so. 58 */ 59 alias LV2_State_Flags = int; 60 enum : int { 61 /** 62 Plain Old Data. 63 64 Values with this flag contain no pointers or references to other areas 65 of memory. It is safe to copy POD values with a simple memcpy and store 66 them for the duration of the process. A POD value is not necessarily 67 safe to trasmit between processes or machines (e.g. filenames are POD), 68 see LV2_STATE_IS_PORTABLE for details. 69 70 Implementations MUST NOT attempt to copy or serialise a non-POD value if 71 they do not understand its type (and thus know how to correctly do so). 72 */ 73 LV2_STATE_IS_POD = 1, 74 75 /** 76 Portable (architecture independent) data. 77 78 Values with this flag are in a format that is usable on any 79 architecture. A portable value saved on one machine can be restored on 80 another machine regardless of architecture. The format of portable 81 values MUST NOT depend on architecture-specific properties like 82 endianness or alignment. Portable values MUST NOT contain filenames. 83 */ 84 LV2_STATE_IS_PORTABLE = 1 << 1, 85 86 /** 87 Native data. 88 89 This flag is used by the host to indicate that the saved data is only 90 going to be used locally in the currently running process (e.g. for 91 instance duplication or snapshots), so the plugin should use the most 92 efficient representation possible and not worry about serialisation 93 and portability. 94 */ 95 LV2_STATE_IS_NATIVE = 1 << 2 96 } 97 98 /** A status code for state functions. */ 99 alias LV2_State_Status = int; 100 enum : int { 101 LV2_STATE_SUCCESS = 0, /**< Completed successfully. */ 102 LV2_STATE_ERR_UNKNOWN = 1, /**< Unknown error. */ 103 LV2_STATE_ERR_BAD_TYPE = 2, /**< Failed due to unsupported type. */ 104 LV2_STATE_ERR_BAD_FLAGS = 3, /**< Failed due to unsupported flags. */ 105 LV2_STATE_ERR_NO_FEATURE = 4, /**< Failed due to missing features. */ 106 LV2_STATE_ERR_NO_PROPERTY = 5, /**< Failed due to missing property. */ 107 LV2_STATE_ERR_NO_SPACE = 6 /**< Failed due to insufficient space. */ 108 } 109 110 /** 111 A host-provided function to store a property. 112 @param handle Must be the handle passed to LV2_State_Interface.save(). 113 @param key The key to store `value` under (URID). 114 @param value Pointer to the value to be stored. 115 @param size The size of `value` in bytes. 116 @param type The type of `value` (URID). 117 @param flags LV2_State_Flags for `value`. 118 @return 0 on success, otherwise a non-zero error code. 119 120 The host passes a callback of this type to LV2_State_Interface.save(). This 121 callback is called repeatedly by the plugin to store all the properties that 122 describe its current state. 123 124 DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY. Best is to use keys from 125 existing vocabularies. If nothing appropriate is available, use http URIs 126 that point to somewhere you can host documents so documentation can be made 127 resolvable (e.g. a child of the plugin or project URI). If this is not 128 possible, invent a URN scheme, e.g. urn:myproj:whatever. The plugin MUST 129 NOT pass an invalid URI key. 130 131 The host MAY fail to store a property for whatever reason, but SHOULD 132 store any property that is LV2_STATE_IS_POD and LV2_STATE_IS_PORTABLE. 133 Implementations SHOULD use the types from the LV2 Atom extension 134 (http://lv2plug.in/ns/ext/atom) wherever possible. The plugin SHOULD 135 attempt to fall-back and avoid the error if possible. 136 137 Note that `size` MUST be > 0, and `value` MUST point to a valid region of 138 memory `size` bytes long (this is required to make restore unambiguous). 139 140 The plugin MUST NOT attempt to use this function outside of the 141 LV2_State_Interface.restore() context. 142 */ 143 alias LV2_State_Store_Function = LV2_State_Status function( 144 LV2_State_Handle handle, 145 uint32_t key, 146 const void* value, 147 size_t size, 148 uint32_t type, 149 uint32_t flags); 150 151 /** 152 A host-provided function to retrieve a property. 153 @param handle Must be the handle passed to LV2_State_Interface.restore(). 154 @param key The key of the property to retrieve (URID). 155 @param size (Output) If non-NULL, set to the size of the restored value. 156 @param type (Output) If non-NULL, set to the type of the restored value. 157 @param flags (Output) If non-NULL, set to the flags for the restored value. 158 @return A pointer to the restored value (object), or NULL if no value 159 has been stored under `key`. 160 161 A callback of this type is passed by the host to 162 LV2_State_Interface.restore(). This callback is called repeatedly by the 163 plugin to retrieve any properties it requires to restore its state. 164 165 The returned value MUST remain valid until LV2_State_Interface.restore() 166 returns. The plugin MUST NOT attempt to use this function, or any value 167 returned from it, outside of the LV2_State_Interface.restore() context. 168 */ 169 alias LV2_State_Retrieve_Function = const void* function( 170 LV2_State_Handle handle, 171 uint32_t key, 172 size_t* size, 173 uint32_t* type, 174 uint32_t* flags); 175 176 /** 177 LV2 Plugin State Interface. 178 179 When the plugin's extension_data is called with argument 180 LV2_STATE__interface, the plugin MUST return an LV2_State_Interface 181 structure, which remains valid for the lifetime of the plugin. 182 183 The host can use the contained function pointers to save and restore the 184 state of a plugin instance at any time, provided the threading restrictions 185 of the functions are met. 186 187 Stored data is only guaranteed to be compatible between instances of plugins 188 with the same URI (i.e. if a change to a plugin would cause a fatal error 189 when restoring state saved by a previous version of that plugin, the plugin 190 URI MUST change just as it must when ports change incompatibly). Plugin 191 authors should consider this possibility, and always store sensible data 192 with meaningful types to avoid such problems in the future. 193 */ 194 struct _LV2_State_Interface { 195 /** 196 Save plugin state using a host-provided `store` callback. 197 198 @param instance The instance handle of the plugin. 199 @param store The host-provided store callback. 200 @param handle An opaque pointer to host data which MUST be passed as the 201 handle parameter to `store` if it is called. 202 @param flags Flags describing desired properties of this save. These 203 flags may be used to determine the most appropriate values to store. 204 @param features Extensible parameter for passing any additional 205 features to be used for this save. 206 207 The plugin is expected to store everything necessary to completely 208 restore its state later. Plugins SHOULD store simple POD data whenever 209 possible, and consider the possibility of state being restored much 210 later on a different machine. 211 212 The `handle` pointer and `store` function MUST NOT be used 213 beyond the scope of save(). 214 215 This function has its own special threading class: it may not be called 216 concurrently with any "Instantiation" function, but it may be called 217 concurrently with functions in any other class, unless the definition of 218 that class prohibits it (e.g. it may not be called concurrently with a 219 "Discovery" function, but it may be called concurrently with an "Audio" 220 function. The plugin is responsible for any locking or lock-free 221 techniques necessary to make this possible. 222 223 Note that in the simple case where state is only modified by restore(), 224 there are no synchronization issues since save() is never called 225 concurrently with restore() (though run() may read it during a save). 226 227 Plugins that dynamically modify state while running, however, must take 228 care to do so in such a way that a concurrent call to save() will save a 229 consistent representation of plugin state for a single instant in time. 230 */ 231 LV2_State_Status function(LV2_Handle instance, 232 LV2_State_Store_Function store, 233 LV2_State_Handle handle, 234 uint32_t flags, 235 const(LV2_Feature*)* features) save; 236 237 /** 238 Restore plugin state using a host-provided `retrieve` callback. 239 240 @param instance The instance handle of the plugin. 241 @param retrieve The host-provided retrieve callback. 242 @param handle An opaque pointer to host data which MUST be passed as the 243 handle parameter to `retrieve` if it is called. 244 @param flags Currently unused. 245 @param features Extensible parameter for passing any additional 246 features to be used for this restore. 247 248 The plugin MAY assume a restored value was set by a previous call to 249 LV2_State_Interface.save() by a plugin with the same URI. 250 251 The plugin MUST gracefully fall back to a default value when a value can 252 not be retrieved. This allows the host to reset the plugin state with 253 an empty map. 254 255 The `handle` pointer and `store` function MUST NOT be used 256 beyond the scope of restore(). 257 258 This function is in the "Instantiation" threading class as defined by 259 LV2. This means it MUST NOT be called concurrently with any other 260 function on the same plugin instance. 261 */ 262 LV2_State_Status function(LV2_Handle instance, 263 LV2_State_Retrieve_Function retrieve, 264 LV2_State_Handle handle, 265 uint32_t flags, 266 const(LV2_Feature*)* features) restore; 267 }; 268 alias LV2_State_Interface = _LV2_State_Interface; 269 270 /** 271 Feature data for state:mapPath (@ref LV2_STATE__mapPath). 272 */ 273 struct LV2_State_Map_Path { 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 @param handle MUST be the `handle` member of this struct. 282 @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 in plugin state. The returned value is an abstract path which MAY not 287 be an actual file system path; absolute_path() MUST be used to map 288 it to an actual path in order to use the file. 289 290 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 absolute_path(). 293 294 This function may only be called within the context of 295 LV2_State_Interface methods. The caller is responsible for freeing the 296 returned value with free(). 297 */ 298 char* function(LV2_State_Map_Path_Handle handle, 299 const char* absolute_path) abstract_path; 300 301 /** 302 Map an abstract path from plugin state to an absolute path. 303 @param handle MUST be the `handle` member of this struct. 304 @param abstract_path An abstract path (e.g. a path from plugin state). 305 @return An absolute file system path. 306 307 The plugin MUST use this function in order to actually open or otherwise 308 use any paths loaded from plugin state. 309 310 This function may only be called within the context of 311 LV2_State_Interface methods. The caller is responsible for freeing the 312 returned value with free(). 313 */ 314 char* function(LV2_State_Map_Path_Handle handle, 315 const char* abstract_path) absolute_path; 316 }; 317 318 /** 319 Feature data for state:makePath (@ref LV2_STATE__makePath). 320 */ 321 struct LV2_State_Make_Path { 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 `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* function(LV2_State_Make_Path_Handle handle, 351 const char* path) path; 352 }; 353 354 } /* extern "C" */