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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 */