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authorBent Bisballe Nyeng <deva@aasimon.org>2012-01-23 20:37:20 +0100
committerBent Bisballe Nyeng <deva@aasimon.org>2012-01-23 20:37:20 +0100
commit4a4d0a84bb1b80555052f59c1a4addc870ce5fda (patch)
tree513185d2eb849597040bd189714244afc0e7ce3a /lv2/lv2_persist.h
parentcdbae7738c35268fd9a208be0618c4ea11475935 (diff)
Make plugin store its state. Connect state and GUI (and use GUI)
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+/*
+ Copyright 2010-2011 David Robillard <http://drobilla.net>
+ Copyright 2010 Leonard Ritter <paniq@paniq.org>
+
+ This header is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published
+ by the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This header is distributed in the hope that it will be useful, but WITHOUT
+ ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this header; if not, write to the Free Software Foundation,
+ Inc., 59 Temple Place, Suite 330, Boston, MA 01222-1307 USA
+*/
+
+/**
+ @file
+ C API for the LV2 Persist extension <http://lv2plug.in/ns/ext/persist>.
+*/
+
+#ifndef LV2_PERSIST_H
+#define LV2_PERSIST_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_PERSIST_URI "http://lv2plug.in/ns/ext/persist"
+
+/**
+ 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-persistent 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_PERSIST_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_PERSIST_IS_PORTABLE = 1 << 1
+
+} LV2_Persist_Flags;
+
+/**
+ A host-provided function to store a property.
+ @param callback_data Must be the callback_data passed to LV2_Persist.save().
+ @param key The key (predicate) to store @a value under (URI mapped integer).
+ @param value Pointer to the value (object) to be stored.
+ @param size The size of the data at @a value in bytes.
+ @param type The type of @a value (URI).
+ @param flags LV2_Persist_Flags for @a value.
+ @return 0 on success, otherwise a non-zero error code.
+
+ The host passes a callback of this type to LV2_Persist.save(). This callback
+ is called repeatedly by the plugin within LV2_Persist.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_PERSIST_IS_POD and/or LV2_PERSIST_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 @a size MUST be > 0, and @a value MUST point to a valid region of
+ memory @a size bytes long (this is required to make restore unambiguous).
+
+ The plugin MUST NOT attempt to use this function outside of the
+ LV2_Persist.restore() context.
+*/
+typedef int (*LV2_Persist_Store_Function)(
+ void* callback_data,
+ uint32_t key,
+ const void* value,
+ size_t size,
+ uint32_t type,
+ uint32_t flags);
+
+/**
+ A host-provided function to retrieve a property.
+ @param callback_data Must be the callback_data passed to LV2_Persist.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_Persist_Flags for
+ the returned value.
+ @return A pointer to the restored value (object), or NULL if no value
+ has been stored under @a key.
+
+ A callback of this type is passed by the host to LV2_Persist.restore(). This
+ callback is called repeatedly by the plugin within LV2_Persist.restore() to
+ retrieve any properties it requires to restore its state.
+
+ The returned value MUST remain valid until LV2_Persist.restore() returns.
+
+ The plugin MUST NOT attempt to use this function, or any value returned from
+ it, outside of the LV2_Persist.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_Persist_Retrieve_Function)(
+ void* callback_data,
+ uint32_t key,
+ size_t* size,
+ uint32_t* type,
+ uint32_t* flags);
+
+/**
+ Persist Extension Data.
+
+ When the plugin's extension_data is called with argument LV2_PERSIST_URI,
+ the plugin MUST return an LV2_Persist 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_Persist {
+
+ /**
+ Save plugin state using a host-provided @a store callback.
+
+ @param instance The instance handle of the plugin.
+ @param store The host-provided store callback.
+ @param callback_data An opaque pointer to host data, e.g. the map or
+ file where the values are to be stored. If @a store is called,
+ this MUST be passed as its callback_data parameter.
+
+ 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 @a callback_data pointer and @a 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_Persist_Store_Function store,
+ void* callback_data);
+
+ /**
+ Restore plugin state using a host-provided @a retrieve callback.
+
+ @param instance The instance handle of the plugin.
+ @param retrieve The host-provided retrieve callback.
+ @param callback_data An opaque pointer to host data, e.g. the map or
+ file from which the values are to be restored. If @a retrieve is
+ called, this MUST be passed as its callback_data parameter.
+
+ The plugin MAY assume a restored value was set by a previous call to
+ LV2_Persist.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 @a callback_data pointer and @a 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_Persist_Retrieve_Function retrieve,
+ void* callback_data);
+
+} LV2_Persist;
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* LV2_PERSIST_H */