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 nothrow @nogc: 32 33 import core.stdc.stddef; 34 import core.stdc.stdint; 35 36 import dplug.lv2.lv2; 37 38 enum LV2_STATE_URI = "http://lv2plug.in/ns/ext/state"; ///< http://lv2plug.in/ns/ext/state 39 enum LV2_STATE_PREFIX = LV2_STATE_URI ~ "#"; ///< http://lv2plug.in/ns/ext/state# 40 41 enum LV2_STATE__State = LV2_STATE_PREFIX ~ "State"; ///< http://lv2plug.in/ns/ext/state#State 42 enum LV2_STATE__interface = LV2_STATE_PREFIX ~ "interface"; ///< http://lv2plug.in/ns/ext/state#interface 43 enum LV2_STATE__loadDefaultState = LV2_STATE_PREFIX ~ "loadDefaultState"; ///< http://lv2plug.in/ns/ext/state#loadDefaultState 44 enum LV2_STATE__makePath = LV2_STATE_PREFIX ~ "makePath"; ///< http://lv2plug.in/ns/ext/state#makePath 45 enum LV2_STATE__mapPath = LV2_STATE_PREFIX ~ "mapPath"; ///< http://lv2plug.in/ns/ext/state#mapPath 46 enum LV2_STATE__state = LV2_STATE_PREFIX ~ "state"; ///< http://lv2plug.in/ns/ext/state#state 47 enum LV2_STATE__threadSafeRestore = LV2_STATE_PREFIX ~ "threadSafeRestore"; ///< http://lv2plug.in/ns/ext/state#threadSafeRestore 48 49 alias LV2_State_Handle = void*; ///b< 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 : LV2_State_Flags { 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 transmit 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 extern(C) 144 { 145 alias LV2_State_Store_Function = LV2_State_Status function(LV2_State_Handle handle, uint key, const(void)* value, size_t size, uint type, uint flags); 146 } 147 148 /** 149 A host-provided function to retrieve a property. 150 @param handle Must be the handle passed to LV2_State_Interface.restore(). 151 @param key The key of the property to retrieve (URID). 152 @param size (Output) If non-NULL, set to the size of the restored value. 153 @param type (Output) If non-NULL, set to the type of the restored value. 154 @param flags (Output) If non-NULL, set to the flags for the restored value. 155 @return A pointer to the restored value (object), or NULL if no value 156 has been stored under `key`. 157 158 A callback of this type is passed by the host to 159 LV2_State_Interface.restore(). This callback is called repeatedly by the 160 plugin to retrieve any properties it requires to restore its state. 161 162 The returned value MUST remain valid until LV2_State_Interface.restore() 163 returns. The plugin MUST NOT attempt to use this function, or any value 164 returned from it, outside of the LV2_State_Interface.restore() context. 165 */ 166 extern(C) 167 { 168 alias LV2_State_Retrieve_Function = const(void)* function(LV2_State_Handle handle, uint key, size_t* size, uint* type, uint* flags); 169 } 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 struct LV2_State_Interface 190 { 191 nothrow @nogc: 192 /** 193 Save plugin state using a host-provided `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 `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 `handle` pointer and `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 extern(C) 229 { 230 alias saveFun_t = LV2_State_Status function(LV2_Handle instance, 231 LV2_State_Store_Function store, 232 LV2_State_Handle handle, 233 uint flags, 234 const(LV2_Feature*)* features); 235 } 236 saveFun_t save; 237 238 /** 239 Restore plugin state using a host-provided `retrieve` callback. 240 241 @param instance The instance handle of the plugin. 242 @param retrieve The host-provided retrieve callback. 243 @param handle An opaque pointer to host data which MUST be passed as the 244 handle parameter to `retrieve` if it is called. 245 @param flags Currently unused. 246 @param features Extensible parameter for passing any additional 247 features to be used for this restore. 248 249 The plugin MAY assume a restored value was set by a previous call to 250 LV2_State_Interface.save() by a plugin with the same URI. 251 252 The plugin MUST gracefully fall back to a default value when a value can 253 not be retrieved. This allows the host to reset the plugin state with 254 an empty map. 255 256 The `handle` pointer and `store` function MUST NOT be used 257 beyond the scope of restore(). 258 259 This function is in the "Instantiation" threading class as defined by 260 LV2. This means it MUST NOT be called concurrently with any other 261 function on the same plugin instance. 262 */ 263 extern(C) 264 { 265 alias restoreFun_t = LV2_State_Status function(LV2_Handle instance, 266 LV2_State_Retrieve_Function retrieve, 267 LV2_State_Handle handle, 268 uint flags, 269 const(LV2_Feature*)* features); 270 } 271 restoreFun_t restore; 272 273 };