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Diffstat (limited to 'lv2/state/state.h')
| -rw-r--r-- | lv2/state/state.h | 363 |
1 files changed, 363 insertions, 0 deletions
diff --git a/lv2/state/state.h b/lv2/state/state.h new file mode 100644 index 0000000..ffc40d1 --- /dev/null +++ b/lv2/state/state.h @@ -0,0 +1,363 @@ +/* + Copyright 2010-2016 David Robillard <http://drobilla.net> + Copyright 2010 Leonard Ritter <paniq@paniq.org> + + Permission to use, copy, modify, and/or distribute this software for any + purpose with or without fee is hereby granted, provided that the above + copyright notice and this permission notice appear in all copies. + + THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +*/ + +/** + @defgroup state State + + An interface for LV2 plugins to save and restore state, see + <http://lv2plug.in/ns/ext/state> for details. + + @{ +*/ + +#ifndef LV2_STATE_H +#define LV2_STATE_H + +#include <stddef.h> +#include <stdint.h> + +#include "lv2/core/lv2.h" + +#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state" ///< http://lv2plug.in/ns/ext/state +#define LV2_STATE_PREFIX LV2_STATE_URI "#" ///< http://lv2plug.in/ns/ext/state# + +#define LV2_STATE__State LV2_STATE_PREFIX "State" ///< http://lv2plug.in/ns/ext/state#State +#define LV2_STATE__interface LV2_STATE_PREFIX "interface" ///< http://lv2plug.in/ns/ext/state#interface +#define LV2_STATE__loadDefaultState LV2_STATE_PREFIX "loadDefaultState" ///< http://lv2plug.in/ns/ext/state#loadDefaultState +#define LV2_STATE__makePath LV2_STATE_PREFIX "makePath" ///< http://lv2plug.in/ns/ext/state#makePath +#define LV2_STATE__mapPath LV2_STATE_PREFIX "mapPath" ///< http://lv2plug.in/ns/ext/state#mapPath +#define LV2_STATE__state LV2_STATE_PREFIX "state" ///< http://lv2plug.in/ns/ext/state#state +#define LV2_STATE__threadSafeRestore LV2_STATE_PREFIX "threadSafeRestore" ///< http://lv2plug.in/ns/ext/state#threadSafeRestore +#define LV2_STATE__StateChanged LV2_STATE_PREFIX "StateChanged" ///< http://lv2plug.in/ns/ext/state#StateChanged + +#ifdef __cplusplus +extern "C" { +#else +# include <stdbool.h> +#endif + +typedef void* LV2_State_Handle; ///< Opaque handle for state save/restore +typedef void* LV2_State_Map_Path_Handle; ///< Opaque handle for state:mapPath feature +typedef void* LV2_State_Make_Path_Handle; ///< Opaque handle for state:makePath feature + +/** + Flags describing value characteristics. + + These flags are used along with the value's type URI to determine how to + (de-)serialise the value data, or whether it is even possible to do so. +*/ +typedef enum { + /** + Plain Old Data. + + Values with this flag contain no pointers or references to other areas + of memory. It is safe to copy POD values with a simple memcpy and store + them for the duration of the process. A POD value is not necessarily + safe to trasmit between processes or machines (e.g. filenames are POD), + see LV2_STATE_IS_PORTABLE for details. + + Implementations MUST NOT attempt to copy or serialise a non-POD value if + they do not understand its type (and thus know how to correctly do so). + */ + LV2_STATE_IS_POD = 1, + + /** + Portable (architecture independent) data. + + Values with this flag are in a format that is usable on any + architecture. A portable value saved on one machine can be restored on + another machine regardless of architecture. The format of portable + values MUST NOT depend on architecture-specific properties like + endianness or alignment. Portable values MUST NOT contain filenames. + */ + LV2_STATE_IS_PORTABLE = 1 << 1, + + /** + Native data. + + This flag is used by the host to indicate that the saved data is only + going to be used locally in the currently running process (e.g. for + instance duplication or snapshots), so the plugin should use the most + efficient representation possible and not worry about serialisation + and portability. + */ + LV2_STATE_IS_NATIVE = 1 << 2 +} LV2_State_Flags; + +/** A status code for state functions. */ +typedef enum { + LV2_STATE_SUCCESS = 0, /**< Completed successfully. */ + LV2_STATE_ERR_UNKNOWN = 1, /**< Unknown error. */ + LV2_STATE_ERR_BAD_TYPE = 2, /**< Failed due to unsupported type. */ + LV2_STATE_ERR_BAD_FLAGS = 3, /**< Failed due to unsupported flags. */ + LV2_STATE_ERR_NO_FEATURE = 4, /**< Failed due to missing features. */ + LV2_STATE_ERR_NO_PROPERTY = 5, /**< Failed due to missing property. */ + LV2_STATE_ERR_NO_SPACE = 6 /**< Failed due to insufficient space. */ +} LV2_State_Status; + +/** + A host-provided function to store a property. + @param handle Must be the handle passed to LV2_State_Interface.save(). + @param key The key to store `value` under (URID). + @param value Pointer to the value to be stored. + @param size The size of `value` in bytes. + @param type The type of `value` (URID). + @param flags LV2_State_Flags for `value`. + @return 0 on success, otherwise a non-zero error code. + + The host passes a callback of this type to LV2_State_Interface.save(). This + callback is called repeatedly by the plugin to store all the properties that + describe its current state. + + DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY. Best is to use keys from + existing vocabularies. If nothing appropriate is available, use http URIs + that point to somewhere you can host documents so documentation can be made + resolvable (e.g. a child of the plugin or project URI). If this is not + possible, invent a URN scheme, e.g. urn:myproj:whatever. The plugin MUST + NOT pass an invalid URI key. + + The host MAY fail to store a property for whatever reason, but SHOULD + store any property that is LV2_STATE_IS_POD and LV2_STATE_IS_PORTABLE. + Implementations SHOULD use the types from the LV2 Atom extension + (http://lv2plug.in/ns/ext/atom) wherever possible. The plugin SHOULD + attempt to fall-back and avoid the error if possible. + + Note that `size` MUST be > 0, and `value` MUST point to a valid region of + memory `size` bytes long (this is required to make restore unambiguous). + + The plugin MUST NOT attempt to use this function outside of the + LV2_State_Interface.restore() context. +*/ +typedef LV2_State_Status (*LV2_State_Store_Function)( + LV2_State_Handle handle, + uint32_t key, + const void* value, + size_t size, + uint32_t type, + uint32_t flags); + +/** + A host-provided function to retrieve a property. + @param handle Must be the handle passed to LV2_State_Interface.restore(). + @param key The key of the property to retrieve (URID). + @param size (Output) If non-NULL, set to the size of the restored value. + @param type (Output) If non-NULL, set to the type of the restored value. + @param flags (Output) If non-NULL, set to the flags for the restored value. + @return A pointer to the restored value (object), or NULL if no value + has been stored under `key`. + + A callback of this type is passed by the host to + LV2_State_Interface.restore(). This callback is called repeatedly by the + plugin to retrieve any properties it requires to restore its state. + + The returned value MUST remain valid until LV2_State_Interface.restore() + returns. The plugin MUST NOT attempt to use this function, or any value + returned from it, outside of the LV2_State_Interface.restore() context. +*/ +typedef const void* (*LV2_State_Retrieve_Function)( + LV2_State_Handle handle, + uint32_t key, + size_t* size, + uint32_t* type, + uint32_t* flags); + +/** + LV2 Plugin State Interface. + + When the plugin's extension_data is called with argument + LV2_STATE__interface, the plugin MUST return an LV2_State_Interface + structure, which remains valid for the lifetime of the plugin. + + The host can use the contained function pointers to save and restore the + state of a plugin instance at any time, provided the threading restrictions + of the functions are met. + + Stored data is only guaranteed to be compatible between instances of plugins + with the same URI (i.e. if a change to a plugin would cause a fatal error + when restoring state saved by a previous version of that plugin, the plugin + URI MUST change just as it must when ports change incompatibly). Plugin + authors should consider this possibility, and always store sensible data + with meaningful types to avoid such problems in the future. +*/ +typedef struct _LV2_State_Interface { + /** + Save plugin state using a host-provided `store` callback. + + @param instance The instance handle of the plugin. + @param store The host-provided store callback. + @param handle An opaque pointer to host data which MUST be passed as the + handle parameter to `store` if it is called. + @param flags Flags describing desired properties of this save. These + flags may be used to determine the most appropriate values to store. + @param features Extensible parameter for passing any additional + features to be used for this save. + + The plugin is expected to store everything necessary to completely + restore its state later. Plugins SHOULD store simple POD data whenever + possible, and consider the possibility of state being restored much + later on a different machine. + + The `handle` pointer and `store` function MUST NOT be used + beyond the scope of save(). + + This function has its own special threading class: it may not be called + concurrently with any "Instantiation" function, but it may be called + concurrently with functions in any other class, unless the definition of + that class prohibits it (e.g. it may not be called concurrently with a + "Discovery" function, but it may be called concurrently with an "Audio" + function. The plugin is responsible for any locking or lock-free + techniques necessary to make this possible. + + Note that in the simple case where state is only modified by restore(), + there are no synchronization issues since save() is never called + concurrently with restore() (though run() may read it during a save). + + Plugins that dynamically modify state while running, however, must take + care to do so in such a way that a concurrent call to save() will save a + consistent representation of plugin state for a single instant in time. + */ + LV2_State_Status (*save)(LV2_Handle instance, + LV2_State_Store_Function store, + LV2_State_Handle handle, + uint32_t flags, + const LV2_Feature *const * features); + + /** + Restore plugin state using a host-provided `retrieve` callback. + + @param instance The instance handle of the plugin. + @param retrieve The host-provided retrieve callback. + @param handle An opaque pointer to host data which MUST be passed as the + handle parameter to `retrieve` if it is called. + @param flags Currently unused. + @param features Extensible parameter for passing any additional + features to be used for this restore. + + The plugin MAY assume a restored value was set by a previous call to + LV2_State_Interface.save() by a plugin with the same URI. + + The plugin MUST gracefully fall back to a default value when a value can + not be retrieved. This allows the host to reset the plugin state with + an empty map. + + The `handle` pointer and `store` function MUST NOT be used + beyond the scope of restore(). + + This function is in the "Instantiation" threading class as defined by + LV2. This means it MUST NOT be called concurrently with any other + function on the same plugin instance. + */ + LV2_State_Status (*restore)(LV2_Handle instance, + LV2_State_Retrieve_Function retrieve, + LV2_State_Handle handle, + uint32_t flags, + const LV2_Feature *const * features); +} LV2_State_Interface; + +/** + Feature data for state:mapPath (@ref LV2_STATE__mapPath). +*/ +typedef struct { + /** + Opaque host data. + */ + LV2_State_Map_Path_Handle handle; + + /** + Map an absolute path to an abstract path for use in plugin state. + @param handle MUST be the `handle` member of this struct. + @param absolute_path The absolute path of a file. + @return An abstract path suitable for use in plugin state. + + The plugin MUST use this function to map any paths that will be stored + in plugin state. The returned value is an abstract path which MAY not + be an actual file system path; absolute_path() MUST be used to map + it to an actual path in order to use the file. + + Plugins MUST NOT make any assumptions about abstract paths except that + they can be mapped back to the absolute path of the "same" file (though + not necessarily the same original path) using absolute_path(). + + This function may only be called within the context of + LV2_State_Interface methods. The caller is responsible for freeing the + returned value with free(). + */ + char* (*abstract_path)(LV2_State_Map_Path_Handle handle, + const char* absolute_path); + + /** + Map an abstract path from plugin state to an absolute path. + @param handle MUST be the `handle` member of this struct. + @param abstract_path An abstract path (e.g. a path from plugin state). + @return An absolute file system path. + + The plugin MUST use this function in order to actually open or otherwise + use any paths loaded from plugin state. + + This function may only be called within the context of + LV2_State_Interface methods. The caller is responsible for freeing the + returned value with free(). + */ + char* (*absolute_path)(LV2_State_Map_Path_Handle handle, + const char* abstract_path); +} LV2_State_Map_Path; + +/** + Feature data for state:makePath (@ref LV2_STATE__makePath). +*/ +typedef struct { + /** + Opaque host data. + */ + LV2_State_Make_Path_Handle handle; + + /** + Return a path the plugin may use to create a new file. + @param handle MUST be the `handle` member of this struct. + @param path The path of the new file within a namespace unique to this + plugin instance. + @return The absolute path to use for the new file. + + This function can be used by plugins to create files and directories, + either at state saving time (if this feature is passed to + LV2_State_Interface.save()) or any time (if this feature is passed to + LV2_Descriptor.instantiate()). + + The host MUST do whatever is necessary for the plugin to be able to + create a file at the returned path (e.g. using fopen), including + creating any leading directories. + + If this function is passed to LV2_Descriptor.instantiate(), it may be + called from any non-realtime context. If it is passed to + LV2_State_Interface.save(), it may only be called within the dynamic + scope of that function call. + + The caller is responsible for freeing the returned value with free(). + */ + char* (*path)(LV2_State_Make_Path_Handle handle, + const char* path); +} LV2_State_Make_Path; + +#ifdef __cplusplus +} /* extern "C" */ +#endif + +#endif /* LV2_STATE_H */ + +/** + @} +*/ |