diff options
Diffstat (limited to 'ext/persist.lv2/persist.h')
| -rw-r--r-- | ext/persist.lv2/persist.h | 97 |
1 files changed, 63 insertions, 34 deletions
diff --git a/ext/persist.lv2/persist.h b/ext/persist.lv2/persist.h index 5ed6c45..17478e8 100644 --- a/ext/persist.lv2/persist.h +++ b/ext/persist.lv2/persist.h @@ -35,34 +35,59 @@ extern "C" { #define LV2_PERSIST_URI "http://lv2plug.in/ns/ext/persist" /** - A host-provided function to store a value under a given key. + 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 subject The subject of this property (URI), or 0 for plugin instance. @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 mapped integer). - @param pod True iff @a value is POD. + @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 key/value records that describe - its current state. - - If @a pod is true, @a value is guaranteed to be architecture-independent POD - (i.e. a region of memory that does not contain pointers or references to - non-persistent resources and can safely be copied and stored with a simple - memcpy). Note that this definition of POD is more strict than exclusively - in-memory definitions since the value MUST be architecture independent; - e.g. endianness must be considered (so basic numeric types are typically NOT - POD). Hosts MAY fail to store the value, particularly if it is - non-POD. Plugins MUST gracefully handle this situation, even though state - may not be fully restored. Hosts SHOULD support any POD value, even if the - host does not know anything about its type. Plugins SHOULD express their - state entirely with POD values whenever possible, and use non-POD values - only where necessary. Plugins SHOULD use common RDF types and/or types from - the Atom extension <http://lv2plug.in/ns/ext/atom> whenever possible since - hosts are likely to already contain the necessary implementation. + 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 statement 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). @@ -71,40 +96,44 @@ extern "C" { LV2_Persist.restore() context. */ typedef int (*LV2_Persist_Store_Function)( - void* callback_data, - const uint32_t key, - const void* value, - size_t size, - uint32_t type, - bool pod); + void* callback_data, + uint32_t subject, + uint32_t key, + const void* value, + size_t size, + uint32_t type, + uint32_t flags); /** - A host-provided function to retrieve a value under a given key. + 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 value to retrieve (URI mapped integer). + @param subject The subject of the property (URI), or 0 for plugin instance. + @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 pod (Output) If non-NULL, set to true iff @a value is POD. + @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 the values of any keys it requires to restore its state. + 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 - correctly do so (e.g. the value is POD, or the plugin understands the type). + 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 subject, uint32_t key, size_t* size, uint32_t* type, - bool* pod); + uint32_t* flags); /** Persist Extension Data. |