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-/*
- Copyright 2010-2011 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.
-*/
-
-/**
- @file
- C API for the LV2 State extension <http://lv2plug.in/ns/ext/state>.
-*/
-
-#ifndef LV2_STATE_H
-#define LV2_STATE_H
-
-#include <stdbool.h>
-#include <stddef.h>
-#include <stdint.h>
-
-#include "lv2/lv2plug.in/ns/lv2core/lv2.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state"
-
-#define LV2_STATE_INTERFACE_URI LV2_STATE_URI "#Interface"
-#define LV2_STATE_PATH_URI LV2_STATE_URI "#Path"
-#define LV2_STATE_MAP_PATH_URI LV2_STATE_URI "#pathMap"
-#define LV2_STATE_MAKE_PATH_URI LV2_STATE_URI "#newPath"
-
-typedef void* LV2_State_Handle;
-typedef void* LV2_State_Map_Path_Handle;
-typedef void* LV2_State_Make_Path_Handle;
-
-/**
- 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 references to non-stateent or
- non-global resources (e.g. pointers, handles, local paths, etc.). It is
- safe to copy POD values with a simple memcpy and store them for use at
- any time in the future on a machine with a compatible architecture
- (e.g. the same endianness and alignment).
-
- 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, i.e. if the value is saved on one machine it can safely be
- restored on another machine regardless of endianness, alignment, etc.
- */
- 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 host-provided function to store a property.
- @param handle Must be the handle passed to LV2_State_Interface.save().
- @param key The key (predicate) to store @c value under (URI mapped integer).
- @param value Pointer to the value (object) to be stored.
- @param size The size of the data at @c value in bytes.
- @param type The type of @c value (URI).
- @param flags LV2_State_Flags for @c 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 within LV2_State_Interface.save() to store all
- the statements that describe its current state.
-
- The host MAY fail to store a property if the type is not understood and is
- not LV2_STATE_IS_POD and/or LV2_STATE_IS_PORTABLE. Implementations are
- encouraged to use POD and portable values (e.g. string literals) wherever
- possible, and use common types (e.g. types from
- http://lv2plug.in/ns/ext/atom) regardless, since hosts are likely to already
- contain the necessary implementation.
-
- Note that @c size MUST be > 0, and @c value MUST point to a valid region of
- memory @c 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 int (*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 (predicate) of the property to retrieve (URI).
- @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 LV2_State_Flags for
- the returned value.
- @return A pointer to the restored value (object), or NULL if no value
- has been stored under @c key.
-
- A callback of this type is passed by the host to
- LV2_State_Interface.restore(). This callback is called repeatedly by the
- plugin within LV2_State_Interface.restore() 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. Returned values
- MAY be copied for later use if necessary, assuming the plugin knows how to
- do so correctly (e.g. the value is POD, or the plugin understands the type).
-*/
-typedef const void* (*LV2_State_Retrieve_Function)(LV2_State_Handle handle,
- uint32_t key,
- size_t* size,
- uint32_t* type,
- uint32_t* flags);
-
-/**
- State Extension Data.
-
- When the plugin's extension_data is called with argument LV2_STATE_URI,
- the plugin MUST return an LV2_State 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
- for the given function are met).
-
- The typical use case is to save the plugin's state when a project is saved,
- and to restore the state when a project has been loaded. Other uses are
- possible (e.g. cloning plugin instances or taking a snapshot of plugin
- state).
-
- 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 compatibility issues in the future.
-*/
-typedef struct _LV2_State_Interface {
-
- /**
- Save plugin state using a host-provided @c 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, e.g. the map or
- file where the values are to be stored. If @c store is called, this MUST
- be passed as its handle parameter.
- @param flags Flags describing desires properties of this save. The
- plugin SHOULD use these values to determine the most appropriate and/or
- efficient serialisation, but is not required to do so.
- @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 (possibly much later, in a different process, on
- a completely different machine, etc.)
-
- The @c handle pointer and @c 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.
- */
- void (*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 @c 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, e.g. the map or
- file from which the values are to be restored. If @c retrieve is
- called, this MUST be passed as its handle parameter.
- @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 @c handle pointer and @c 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.
- */
- void (*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:pathMap (LV2_STATE_MAP_PATH_URI).
-*/
-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 @a 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 files in plugin state. The returned value is an abstract path which
- MAY not be an actual file system path; @ref absolute_path MUST be used
- to map it to an actual path in order to use the file.
-
- Hosts MAY map paths in any way (e.g. by creating symbolic links within
- the plugin's state directory or storing a list of referenced files
- elsewhere). Plugins MUST NOT make any assumptions about abstract paths
- except that they can be mapped back to an absolute path using @ref
- absolute_path.
-
- This function may only be called within the context of
- LV2_State_Interface.save() or LV2_State_Interface.restore(). The caller
- is responsible for freeing the returned value.
- */
- 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 @a handle member of this struct.
- @param abstract_path An abstract path (e.g. a path from plugin state).
- @return An absolute file system path.
-
- Since abstract paths are not necessarily actual file paths (or at least
- not necessarily absolute paths), this function MUST be used in order to
- actually open or otherwise use the file referred to by an abstract path.
-
- This function may only be called within the context of
- LV2_State_Interface.save() or LV2_State_Interface.restore(). The caller
- is responsible for freeing the returned value.
- */
- 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_MAKE_PATH_URI).
-*/
-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 @a handle member of this struct.
- @param path The path of the new file relative to 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 */