diff options
Diffstat (limited to 'lv2/lv2plug.in/ns/ext/state')
| l--------- | lv2/lv2plug.in/ns/ext/state/ext.pc.in | 1 | ||||
| -rw-r--r-- | lv2/lv2plug.in/ns/ext/state/manifest.ttl | 8 | ||||
| -rw-r--r-- | lv2/lv2plug.in/ns/ext/state/state.h | 359 | ||||
| -rw-r--r-- | lv2/lv2plug.in/ns/ext/state/state.ttl | 359 | ||||
| l--------- | lv2/lv2plug.in/ns/ext/state/waf | 1 | ||||
| l--------- | lv2/lv2plug.in/ns/ext/state/wscript | 1 |
6 files changed, 729 insertions, 0 deletions
diff --git a/lv2/lv2plug.in/ns/ext/state/ext.pc.in b/lv2/lv2plug.in/ns/ext/state/ext.pc.in new file mode 120000 index 0000000..03dd044 --- /dev/null +++ b/lv2/lv2plug.in/ns/ext/state/ext.pc.in @@ -0,0 +1 @@ +../../../../../ext.pc.in
\ No newline at end of file diff --git a/lv2/lv2plug.in/ns/ext/state/manifest.ttl b/lv2/lv2plug.in/ns/ext/state/manifest.ttl new file mode 100644 index 0000000..bff9ad5 --- /dev/null +++ b/lv2/lv2plug.in/ns/ext/state/manifest.ttl @@ -0,0 +1,8 @@ +@prefix lv2: <http://lv2plug.in/ns/lv2core#> . +@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . + +<http://lv2plug.in/ns/ext/state> + a lv2:Specification ; + lv2:minorVersion 0 ; + lv2:microVersion 5 ; + rdfs:seeAlso <state.ttl> . diff --git a/lv2/lv2plug.in/ns/ext/state/state.h b/lv2/lv2plug.in/ns/ext/state/state.h new file mode 100644 index 0000000..b450b93 --- /dev/null +++ b/lv2/lv2plug.in/ns/ext/state/state.h @@ -0,0 +1,359 @@ +/* + Copyright 2010-2012 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 <stddef.h> +#include <stdint.h> + +#include "lv2/lv2plug.in/ns/lv2core/lv2.h" + +#ifdef __cplusplus +extern "C" { +#else +# include <stdbool.h> +#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 "#mapPath" +#define LV2_STATE_MAKE_PATH_URI LV2_STATE_URI "#makePath" + +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-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_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. + + 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 you can make + documentation resolvable. 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. + + 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:mapPath (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 */ diff --git a/lv2/lv2plug.in/ns/ext/state/state.ttl b/lv2/lv2plug.in/ns/ext/state/state.ttl new file mode 100644 index 0000000..6c0656a --- /dev/null +++ b/lv2/lv2plug.in/ns/ext/state/state.ttl @@ -0,0 +1,359 @@ +# LV2 State Extension +# Copyright 2010-2012 David Robillard <d@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. + +@prefix dcs: <http://ontologi.es/doap-changeset#> . +@prefix doap: <http://usefulinc.com/ns/doap#> . +@prefix foaf: <http://xmlns.com/foaf/0.1/> . +@prefix lv2: <http://lv2plug.in/ns/lv2core#> . +@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . +@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . +@prefix state: <http://lv2plug.in/ns/ext/state#> . + +<http://drobilla.net/drobilla#me> + a foaf:Person ; + foaf:name "David Robillard" ; + foaf:homepage <http://drobilla.net/> ; + foaf:mbox <mailto:d@drobilla.net> ; + rdfs:seeAlso <http://drobilla.net/drobilla> . + +<http://lv2plug.in/ns/ext/state> + a lv2:Specification ; + doap:name "LV2 State" ; + doap:shortdesc "An interface for LV2 plugins to save and restore state." ; + doap:license <http://opensource.org/licenses/isc> ; + doap:release [ + doap:revision "0.5" ; + doap:created "2012-01-29" ; + dcs:blame <http://drobilla.net/drobilla#me> + ] ; + doap:developer [ + a foaf:Person ; + foaf:name "Leonard Ritter" ; + foaf:homepage <http://paniq.org> + ] ; + doap:maintainer [ + a foaf:Person ; + foaf:name "David Robillard" ; + foaf:homepage <http://drobilla.net/> ; + rdfs:seeAlso <http://drobilla.net/drobilla.rdf> + ] ; + lv2:documentation """ +<p>This extension provides a simple mechanism for plugins to save and restore +state across instances, allowing hosts to save and restore a plugin instance's +state at any time. The goal is for an instance's state to be +<em>completely</em> described by port values (as with all LV2 plugins) and a +dictionary.</p> + +<p>The <q>state</q> described by this extension is conceptually a simple +key:value dictionary, where keys are URIDs (URIs mapped to integers) and values +are type-tagged blobs of any type. A single key:value pair is called a +<q>property</q>. To implement state, the plugin provides a state:Interface to +the host. To save or restore, the host calls LV2_State_Interface::save() or +LV2_State_Interface::restore(), passing a callback to be used for handling a +single property. The host is free to implement property storage and retrieval +in any way.</p> + +<p>This state model is simple yet has many benefits:</p> +<ul> + <li>URID keys provide both fast performance and RDF compatibility.</li> + <li>Fully extensible, no limitations on keys or value types.</li> + <li>Easy to serialise in many formats (e.g. any RDF syntax, plain + text, JSON, XML, key:value databases, SQL, s-expressions, etc.).</li> + <li>Elegantly described in Turtle, which is useful for describing presets + or default state in LV2 data files (the predicate state:state is provided + for this purpose).</li> + <li>Does not impose any file formats, data structures, or file system + requirements.</li> + <li>Suitable for portable persistent state as well as fast in-memory + snapshots.</li> + <li>Easily stored in a typical <q>map</q> or <q>dictionary</q> data + structure.</li> + <li>Keys may be defined by extensions and used by several plugins, + making state meaningful enabling dynamic state control.</li> +</ul> + +<p>Implementations or further extensions which work with plugin state +(including dynamic plugin control) SHOULD work entirely within this model. +That is, <strong>do not complicate the state model</strong>. <em>All</em> +information required to express an instance's state at any given time can, and +should, be expressed within this model.</p> + +<h3>Plugin Code Example</h3> + +<pre class="c-code"> +#define NS_EG "http://example.org/" +#define NS_ATOM "http://lv2plug.in/ns/ext/atom#" + +LV2_Handle my_instantiate(...) +{ + MyPlugin* plugin = ...; + plugin->uris.atom_String = map_uri(NS_ATOM "String"); + plugin->uris.eg_greeting = map_uri(NS_EG "greeting"); + plugin->state.greeting = strdup("Hello"); + return plugin; +} + +void my_save(LV2_Handle instance, + LV2_State_Store_Function store, + void* handle, + uint32_t flags, + const LV2_Feature *const * features) +{ + MyPlugin* plugin = (MyPlugin*)instance; + const char* greeting = plugin->state.greeting; + + store(handle, + plugin->uris.eg_greeting, + greeting, + strlen(greeting) + 1, + plugin->uris.atom_String, + LV2_STATE_IS_POD | LV2_STATE_IS_PORTABLE); +} + +void my_restore(LV2_Handle instance, + LV2_State_Retrieve_Function retrieve, + void* handle, + uint32_t flags, + const LV2_Feature *const * features) +{ + MyPlugin* plugin = (MyPlugin*)instance; + + size_t size; + uint32_t type; + uint32_t flags; + const char* greeting = retrieve( + handle, plugin->uris.eg_greeting, &size, &type, &flags); + + if (greeting) { + free(plugin->state->greeting); + plugin->state->greeting = strdup(greeting); + } else { + plugin->state->greeting = strdup("Hello"); + } +} + +const void* my_extension_data(const char* uri) +{ + static const LV2_State_Interface state_iface = { my_save, my_restore }; + if (!strcmp(uri, LV2_STATE_INTERFACE_URI)) { + return &state_iface; + } +} +</pre> + +<h3>Host Code Example</h3> + +<pre class="c-code"> +int store_callback(void* handle, + uint32_t key, + const void* value, + size_t size, + uint32_t type, + uint32_t flags) +{ + if ((flags & LV2_STATE_IS_POD)) { + /* We only care about POD since we're keeping state in memory only. + If this was for disk or network storage/transmission, + LV2_STATE_IS_PORTABLE would have to be checked as well. + */ + Map* state_map = (Map*)handle; + state_map->insert(key, Value(copy(value), size, type, pod)); + return 0; + } else { + return 1; /* Non-POD events are unsupported. */ + } +} + +Map get_plugin_state(LV2_Handle instance) +{ + LV2_State* state = instance.extension_data("http://lv2plug.in/ns/ext/state"); + Map state_map; + /** Request a fast/native/POD save, since we're just copying in memory */ + state.save(instance, store_callback, &state_map, + LV2_STATE_IS_POD|LV2_STATE_IS_NATIVE); + return state_map; +} +</pre> + +<h3>Referring to Existing Files</h3> + +<p>Plugins may need to refer to files (e.g. loaded samples) in their state. +This is done by storing the file's path as a property just like any other +value. However, there are some rules which MUST be followed when storing +paths, see <a href="#mapPath">state:mapPath</a> for details.</p> + +<h3>Creating New Files or Directories</h3> + +<p>Implementations are strongly encouraged to avoid the use of files and simply +store all state as properties whenever possible. However, occasionally the +ability to create files is necessary. The feature <a +href="#newPath">state:newPath</a> makes this possible, if it is provided by the +host.</p> +""" . + +state:Interface + a rdfs:Class ; + rdfs:subClassOf lv2:ExtensionData ; + lv2:documentation """ +<p>A structure (LV2_State_Interface) which contains functions to be called by +the host to save and restore state. In order to support this extension, the +plugin must return a valid LV2_State_Interface from +LV2_Descriptor::extension_data() when it is called with +LV2_STATE_INTERFACE_URI.</p> + +<p>The plugin data file should describe this like so:</p> +<pre class="turtle-code"> +@prefix state: <http://lv2plug.in/ns/ext/state#> . + +<plugin> + a lv2:Plugin ; + lv2:extensionData state:Interface . +</pre> +""" . + +state:State + a rdfs:Class ; + rdfs:label "Plugin Instance State" ; + lv2:documentation """ +<p>This class is used to express a plugin instance's state in RDF. The +key/value properties of the instance form the predicate/object (respectively) +of triples with a state:State as the subject (see <a +href="#state">state:state</a> for an example). This may be used wherever it is +useful to express a plugin instance's state in RDF (e.g. for serialisation, +storing in a model, or transmitting over a network). Note that this class is +provided because it may be useful for hosts, plugins, or extensions that work +with instance state, but its use is not required to support the LV2 State +extension.</p> +""" . + +state:state + a rdf:Property ; + rdfs:range state:State ; + lv2:documentation """ +<p>Predicate to relate a plugin instance to its State. This may be used +wherever the state of a particular plugin instance needs to be represented. +Note that the domain of this property is unspecified, since LV2 does not define +any RDF class for plugin instance. This predicate may be used wherever it makes +sense to do so, e.g.:</p> +<pre class="turtle-code"> +@prefix eg: <http://example.org/> . + +<plugininstance> + state:state [ + eg:somekey "some value" ; + eg:someotherkey "some other value" ; + eg:favourite-number 2 + ] . +</pre> +<p>Note that this property is provided because it may be useful for hosts, +plugins, or extensions that work with instance state, but its use is not +required to support this extension.</p> +""" . + +state:mapPath + a lv2:Feature ; + rdfs:label "Support for storing paths in files" ; + lv2:documentation """ + +<p>This feature maps absolute paths to/from <q>abstract paths</q> which are +stored in state. To support this feature a host must pass an LV2_Feature with +URI LV2_STATE_MAP_PATH_URI and data pointed to an LV2_State_Map_Path to the +plugin's LV2_State_Interface methods.</p> + +<p>The plugin MUST map <em>all</em> paths stored in its state (including in any +files in its state). This is necessary to enable host to handle file system +references correctly, e.g. for distribution or archival.</p> + +<p>For example, a plugin may write a path to a state file like so:</p> + +<pre class="c-code"> +void write_path(LV2_State_Map_Path* map_path, FILE* myfile, const char* path) +{ + char* abstract_path = map_path->abstract_path(map_path->handle, path); + fprintf(myfile, "%s", abstract_path); + free(abstract_path); +} +</pre> + +<p>Then, later reload the path like so:</p> + +<pre class="c-code"> +char* read_path(LV2_State_Map_Path* map_path, FILE* myfile) +{ + /* Obviously this is not production quality code! */ + char abstract_path[1024]; + fscanf(myfile, "%s", abstract_path); + return map_path->absolute_path(map_path->handle, abstract_path); +} +</pre> +""" . + +state:makePath + a lv2:Feature ; + rdfs:label "Support for creating new files and directories" ; + lv2:documentation """ + +<p>This feature allows plugins to create new files and/or directories. To +support this feature the host passes an LV2_Feature with URI +LV2_STATE_MAKE_PATH_URI and data pointed to an LV2_State_Make_Path to the +plugin. The host may make this feature available only during save by passing +it to LV2_State_Interface::save(), or available any time by passing it to +LV2_Descriptor::instantiate(). If passed to LV2_State_Interface::save(), the +feature MUST NOT be used beyond the scope of that call.</p> + +<p>The plugin is guaranteed a hierarchial namespace unique to that plugin +instance, and may expect the returned path to have the requested path as a +suffix. There is <em>one</em> such namespace, even if the feature is passed to +both LV2_Descriptor::instantiate() <em>and</em> +LV2_State_Interface::save(). Beyond this, the plugin MUST NOT make any +assumptions about the returned paths.</p> + +<p>Like any other paths, the plugin MUST map these paths using <a +href="#mapPath">state:mapPath</a> before storing them in state. The plugin +MUST NOT assume these paths will be available across a save/restore otherwise, +i.e. only mapped paths saved to state are persistent, any other created paths +are temporary.</p> + +<p>For example, a plugin may create a file in a subdirectory like so:</p> + +<pre class="c-code"> +char* save_myfile(LV2_State_Make_Path* make_path) +{ + char* path = make_path->path(make_path->handle, "foo/bar/myfile.txt"); + FILE* myfile = fopen(path, 'w'); + fprintf(myfile, "Hello"); + fclose(myfile); + return path; +} +</pre> +""" . + +state:Path + a rdfs:Class ; + rdfs:label "Path" ; + lv2:documentation """ +<p>A path to a file or directory.</p> + +<p>The format of a state:Path is a C string, possibly escaped or otherwise +restricted in a system-specific manner. This URI (LV2_STATE_PATH_URI), mapped +to an integer, MUST be used as the <code>type</code> parameter for any files +passed to the LV2_State_Store_Function; and will likewise be returned by the +corresponding call to the LV2_State_Retrieve_Function.</p> + +<p>When storing and retrieving a path, the plugin MUST NOT assume the same path +will be restored. However, the restored path will refer to a file with +equivalent contents to the original.</p> +""" . diff --git a/lv2/lv2plug.in/ns/ext/state/waf b/lv2/lv2plug.in/ns/ext/state/waf new file mode 120000 index 0000000..5235032 --- /dev/null +++ b/lv2/lv2plug.in/ns/ext/state/waf @@ -0,0 +1 @@ +../../../../../waf
\ No newline at end of file diff --git a/lv2/lv2plug.in/ns/ext/state/wscript b/lv2/lv2plug.in/ns/ext/state/wscript new file mode 120000 index 0000000..7e2c01b --- /dev/null +++ b/lv2/lv2plug.in/ns/ext/state/wscript @@ -0,0 +1 @@ +../../../../../ext.wscript
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