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Diffstat (limited to 'lv2/ns/ext/state/state.h')
| -rw-r--r-- | lv2/ns/ext/state/state.h | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/lv2/ns/ext/state/state.h b/lv2/ns/ext/state/state.h new file mode 100644 index 0000000..4e1c28a --- /dev/null +++ b/lv2/ns/ext/state/state.h @@ -0,0 +1,258 @@ +/* + 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" + +typedef void* LV2_State_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; + +#ifdef __cplusplus +} /* extern "C" */ +#endif + +#endif /* LV2_STATE_H */ |