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+/*
+ 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 */
+
+/**
+ @}
+*/