379 lines
16 KiB
C
379 lines
16 KiB
C
// Copyright 2010-2016 David Robillard <d@drobilla.net>
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// Copyright 2010 Leonard Ritter <paniq@paniq.org>
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// SPDX-License-Identifier: ISC
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#ifndef LV2_STATE_H
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#define LV2_STATE_H
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/**
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@defgroup state State
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@ingroup lv2
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An interface for LV2 plugins to save and restore state.
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See <http://lv2plug.in/ns/ext/state> for details.
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@{
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*/
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#include "lv2/core/lv2.h"
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#include <stddef.h>
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#include <stdint.h>
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// clang-format off
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#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state" ///< http://lv2plug.in/ns/ext/state
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#define LV2_STATE_PREFIX LV2_STATE_URI "#" ///< http://lv2plug.in/ns/ext/state#
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#define LV2_STATE__State LV2_STATE_PREFIX "State" ///< http://lv2plug.in/ns/ext/state#State
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#define LV2_STATE__interface LV2_STATE_PREFIX "interface" ///< http://lv2plug.in/ns/ext/state#interface
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#define LV2_STATE__loadDefaultState LV2_STATE_PREFIX "loadDefaultState" ///< http://lv2plug.in/ns/ext/state#loadDefaultState
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#define LV2_STATE__freePath LV2_STATE_PREFIX "freePath" ///< http://lv2plug.in/ns/ext/state#freePath
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#define LV2_STATE__makePath LV2_STATE_PREFIX "makePath" ///< http://lv2plug.in/ns/ext/state#makePath
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#define LV2_STATE__mapPath LV2_STATE_PREFIX "mapPath" ///< http://lv2plug.in/ns/ext/state#mapPath
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#define LV2_STATE__state LV2_STATE_PREFIX "state" ///< http://lv2plug.in/ns/ext/state#state
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#define LV2_STATE__threadSafeRestore LV2_STATE_PREFIX "threadSafeRestore" ///< http://lv2plug.in/ns/ext/state#threadSafeRestore
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#define LV2_STATE__StateChanged LV2_STATE_PREFIX "StateChanged" ///< http://lv2plug.in/ns/ext/state#StateChanged
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// clang-format on
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef void* LV2_State_Handle; ///< Opaque handle for state save/restore
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typedef void*
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LV2_State_Free_Path_Handle; ///< Opaque handle for state:freePath feature
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typedef void*
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LV2_State_Map_Path_Handle; ///< Opaque handle for state:mapPath feature
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typedef void*
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LV2_State_Make_Path_Handle; ///< Opaque handle for state:makePath feature
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/**
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Flags describing value characteristics.
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These flags are used along with the value's type URI to determine how to
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(de-)serialise the value data, or whether it is even possible to do so.
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*/
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typedef enum {
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/**
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Plain Old Data.
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Values with this flag contain no pointers or references to other areas
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of memory. It is safe to copy POD values with a simple memcpy and store
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them for the duration of the process. A POD value is not necessarily
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safe to transmit between processes or machines (for example, filenames
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are POD), see LV2_STATE_IS_PORTABLE for details.
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Implementations MUST NOT attempt to copy or serialise a non-POD value if
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they do not understand its type (and thus know how to correctly do so).
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*/
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LV2_STATE_IS_POD = 1U << 0U,
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/**
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Portable (architecture independent) data.
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Values with this flag are in a format that is usable on any
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architecture. A portable value saved on one machine can be restored on
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another machine regardless of architecture. The format of portable
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values MUST NOT depend on architecture-specific properties like
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endianness or alignment. Portable values MUST NOT contain filenames.
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*/
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LV2_STATE_IS_PORTABLE = 1U << 1U,
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/**
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Native data.
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This flag is used by the host to indicate that the saved data is only
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going to be used locally in the currently running process (for things
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like instance duplication or snapshots), so the plugin should use the
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most efficient representation possible and not worry about serialisation
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and portability.
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*/
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LV2_STATE_IS_NATIVE = 1U << 2U
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} LV2_State_Flags;
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/** A status code for state functions. */
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typedef enum {
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LV2_STATE_SUCCESS = 0, /**< Completed successfully. */
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LV2_STATE_ERR_UNKNOWN = 1, /**< Unknown error. */
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LV2_STATE_ERR_BAD_TYPE = 2, /**< Failed due to unsupported type. */
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LV2_STATE_ERR_BAD_FLAGS = 3, /**< Failed due to unsupported flags. */
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LV2_STATE_ERR_NO_FEATURE = 4, /**< Failed due to missing features. */
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LV2_STATE_ERR_NO_PROPERTY = 5, /**< Failed due to missing property. */
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LV2_STATE_ERR_NO_SPACE = 6 /**< Failed due to insufficient space. */
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} LV2_State_Status;
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/**
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A host-provided function to store a property.
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@param handle Must be the handle passed to LV2_State_Interface.save().
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@param key The key to store `value` under (URID).
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@param value Pointer to the value to be stored.
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@param size The size of `value` in bytes.
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@param type The type of `value` (URID).
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@param flags LV2_State_Flags for `value`.
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@return 0 on success, otherwise a non-zero error code.
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The host passes a callback of this type to LV2_State_Interface.save(). This
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callback is called repeatedly by the plugin to store all the properties that
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describe its current state.
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DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY. Best is to use keys from
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existing vocabularies. If nothing appropriate is available, use http URIs
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that point to somewhere you can host documents so documentation can be made
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resolvable (typically a child of the plugin or project URI). If this is not
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possible, invent a URN scheme, e.g. urn:myproj:whatever. The plugin MUST
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NOT pass an invalid URI key.
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The host MAY fail to store a property for whatever reason, but SHOULD
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store any property that is LV2_STATE_IS_POD and LV2_STATE_IS_PORTABLE.
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Implementations SHOULD use the types from the LV2 Atom extension
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(http://lv2plug.in/ns/ext/atom) wherever possible. The plugin SHOULD
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attempt to fall-back and avoid the error if possible.
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Note that `size` MUST be > 0, and `value` MUST point to a valid region of
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memory `size` bytes long (this is required to make restore unambiguous).
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The plugin MUST NOT attempt to use this function outside of the
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LV2_State_Interface.restore() context.
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*/
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typedef LV2_State_Status (*LV2_State_Store_Function)(LV2_State_Handle handle,
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uint32_t key,
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const void* value,
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size_t size,
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uint32_t type,
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uint32_t flags);
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/**
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A host-provided function to retrieve a property.
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@param handle Must be the handle passed to LV2_State_Interface.restore().
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@param key The key of the property to retrieve (URID).
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@param size (Output) If non-NULL, set to the size of the restored value.
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@param type (Output) If non-NULL, set to the type of the restored value.
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@param flags (Output) If non-NULL, set to the flags for the restored value.
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@return A pointer to the restored value (object), or NULL if no value
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has been stored under `key`.
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A callback of this type is passed by the host to
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LV2_State_Interface.restore(). This callback is called repeatedly by the
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plugin to retrieve any properties it requires to restore its state.
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The returned value MUST remain valid until LV2_State_Interface.restore()
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returns. The plugin MUST NOT attempt to use this function, or any value
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returned from it, outside of the LV2_State_Interface.restore() context.
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*/
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typedef const void* (*LV2_State_Retrieve_Function)(LV2_State_Handle handle,
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uint32_t key,
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size_t* size,
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uint32_t* type,
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uint32_t* flags);
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/**
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LV2 Plugin State Interface.
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When the plugin's extension_data is called with argument
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LV2_STATE__interface, the plugin MUST return an LV2_State_Interface
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structure, which remains valid for the lifetime of the plugin.
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The host can use the contained function pointers to save and restore the
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state of a plugin instance at any time, provided the threading restrictions
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of the functions are met.
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Stored data is only guaranteed to be compatible between instances of plugins
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with the same URI (i.e. if a change to a plugin would cause a fatal error
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when restoring state saved by a previous version of that plugin, the plugin
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URI MUST change just as it must when ports change incompatibly). Plugin
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authors should consider this possibility, and always store sensible data
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with meaningful types to avoid such problems in the future.
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*/
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typedef struct {
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/**
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Save plugin state using a host-provided `store` callback.
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@param instance The instance handle of the plugin.
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@param store The host-provided store callback.
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@param handle An opaque pointer to host data which MUST be passed as the
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handle parameter to `store` if it is called.
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@param flags Flags describing desired properties of this save. These
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flags may be used to determine the most appropriate values to store.
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@param features Extensible parameter for passing any additional
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features to be used for this save.
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The plugin is expected to store everything necessary to completely
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restore its state later. Plugins SHOULD store simple POD data whenever
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possible, and consider the possibility of state being restored much
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later on a different machine.
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The `handle` pointer and `store` function MUST NOT be used
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beyond the scope of save().
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This function has its own special threading class: it may not be called
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concurrently with any "Instantiation" function, but it may be called
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concurrently with functions in any other class, unless the definition of
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that class prohibits it (for example, it may not be called concurrently
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with a "Discovery" function, but it may be called concurrently with an
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"Audio" function. The plugin is responsible for any locking or
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lock-free techniques necessary to make this possible.
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Note that in the simple case where state is only modified by restore(),
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there are no synchronization issues since save() is never called
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concurrently with restore() (though run() may read it during a save).
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Plugins that dynamically modify state while running, however, must take
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care to do so in such a way that a concurrent call to save() will save a
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consistent representation of plugin state for a single instant in time.
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*/
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LV2_State_Status (*save)(LV2_Handle instance,
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LV2_State_Store_Function store,
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LV2_State_Handle handle,
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uint32_t flags,
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const LV2_Feature* const* features);
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/**
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Restore plugin state using a host-provided `retrieve` callback.
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@param instance The instance handle of the plugin.
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@param retrieve The host-provided retrieve callback.
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@param handle An opaque pointer to host data which MUST be passed as the
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handle parameter to `retrieve` if it is called.
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@param flags Currently unused.
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@param features Extensible parameter for passing any additional
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features to be used for this restore.
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The plugin MAY assume a restored value was set by a previous call to
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LV2_State_Interface.save() by a plugin with the same URI.
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The plugin MUST gracefully fall back to a default value when a value can
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not be retrieved. This allows the host to reset the plugin state with
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an empty map.
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The `handle` pointer and `store` function MUST NOT be used
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beyond the scope of restore().
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This function is in the "Instantiation" threading class as defined by
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LV2. This means it MUST NOT be called concurrently with any other
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function on the same plugin instance.
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*/
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LV2_State_Status (*restore)(LV2_Handle instance,
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LV2_State_Retrieve_Function retrieve,
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LV2_State_Handle handle,
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uint32_t flags,
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const LV2_Feature* const* features);
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} LV2_State_Interface;
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/**
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Feature data for state:mapPath (@ref LV2_STATE__mapPath).
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*/
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typedef struct {
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/**
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Opaque host data.
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*/
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LV2_State_Map_Path_Handle handle;
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/**
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Map an absolute path to an abstract path for use in plugin state.
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@param handle MUST be the `handle` member of this struct.
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@param absolute_path The absolute path of a file.
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@return An abstract path suitable for use in plugin state.
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The plugin MUST use this function to map any paths that will be stored
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in plugin state. The returned value is an abstract path which MAY not
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be an actual file system path; absolute_path() MUST be used to map
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it to an actual path in order to use the file.
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Plugins MUST NOT make any assumptions about abstract paths except that
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they can be mapped back to the absolute path of the "same" file (though
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not necessarily the same original path) using absolute_path().
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This function may only be called within the context of
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LV2_State_Interface methods. The caller must free the returned value
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with LV2_State_Free_Path.free_path().
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*/
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char* (*abstract_path)(LV2_State_Map_Path_Handle handle,
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const char* absolute_path);
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/**
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Map an abstract path from plugin state to an absolute path.
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@param handle MUST be the `handle` member of this struct.
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@param abstract_path An abstract path (typically from plugin state).
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@return An absolute file system path.
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The plugin MUST use this function in order to actually open or otherwise
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use any paths loaded from plugin state.
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This function may only be called within the context of
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LV2_State_Interface methods. The caller must free the returned value
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with LV2_State_Free_Path.free_path().
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*/
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char* (*absolute_path)(LV2_State_Map_Path_Handle handle,
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const char* abstract_path);
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} LV2_State_Map_Path;
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/**
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Feature data for state:makePath (@ref LV2_STATE__makePath).
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*/
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typedef struct {
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/**
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Opaque host data.
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*/
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LV2_State_Make_Path_Handle handle;
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/**
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Return a path the plugin may use to create a new file.
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@param handle MUST be the `handle` member of this struct.
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@param path The path of the new file within a namespace unique to this
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plugin instance.
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@return The absolute path to use for the new file.
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This function can be used by plugins to create files and directories,
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either at state saving time (if this feature is passed to
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LV2_State_Interface.save()) or any time (if this feature is passed to
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LV2_Descriptor.instantiate()).
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The host MUST do whatever is necessary for the plugin to be able to
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create a file at the returned path (for example, using fopen()),
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including creating any leading directories.
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If this function is passed to LV2_Descriptor.instantiate(), it may be
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called from any non-realtime context. If it is passed to
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LV2_State_Interface.save(), it may only be called within the dynamic
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scope of that function call.
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The caller must free the returned value with
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LV2_State_Free_Path.free_path().
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*/
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char* (*path)(LV2_State_Make_Path_Handle handle, const char* path);
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} LV2_State_Make_Path;
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/**
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Feature data for state:freePath (@ref LV2_STATE__freePath).
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*/
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typedef struct {
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/**
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Opaque host data.
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*/
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LV2_State_Free_Path_Handle handle;
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/**
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Free a path returned by a state feature.
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@param handle MUST be the `handle` member of this struct.
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@param path The path previously returned by a state feature.
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This function can be used by plugins to free paths allocated by the host
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and returned by state features (LV2_State_Map_Path.abstract_path(),
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LV2_State_Map_Path.absolute_path(), and LV2_State_Make_Path.path()).
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*/
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void (*free_path)(LV2_State_Free_Path_Handle handle, char* path);
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} LV2_State_Free_Path;
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#ifdef __cplusplus
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} /* extern "C" */
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#endif
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/**
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@}
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*/
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#endif /* LV2_STATE_H */
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