LV2
1.0.13
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URI Map Feature. More...
Data Fields | |
LV2_URI_Map_Callback_Data | callback_data |
Opaque pointer to host data. | |
uint32_t(* | uri_to_id )(LV2_URI_Map_Callback_Data callback_data, const char *map, const char *uri) |
Get the numeric ID of a URI from the host. | |
URI Map Feature.
To support this feature the host must pass an LV2_Feature struct to the plugin's instantiate method with URI "http://lv2plug.in/ns/ext/uri-map" and data pointed to an instance of this struct.
LV2_URI_Map_Callback_Data LV2_URI_Map_Feature::callback_data |
Opaque pointer to host data.
The plugin MUST pass this to any call to functions in this struct. Otherwise, it must not be interpreted in any way.
uint32_t(* LV2_URI_Map_Feature::uri_to_id)(LV2_URI_Map_Callback_Data callback_data, const char *map, const char *uri) |
Get the numeric ID of a URI from the host.
callback_data | Must be the callback_data member of this struct. |
map | The 'context' of this URI. Certain extensions may define a URI that must be passed here with certain restrictions on the return value (e.g. limited range). This value may be NULL if the plugin needs an ID for a URI in general. Extensions SHOULD NOT define a context unless there is a specific need to do so, e.g. to restrict the range of the returned value. |
uri | The URI to be mapped to an integer ID. |
This function is referentially transparent; any number of calls with the same arguments is guaranteed to return the same value over the life of a plugin instance (though the same URI may return different values with a different map parameter). However, this function is not necessarily very fast: plugins SHOULD cache any IDs they might need in performance critical situations.
The return value 0 is reserved and indicates that an ID for that URI could not be created for whatever reason. Extensions MAY define more precisely what this means in a certain context, but in general plugins SHOULD handle this situation as gracefully as possible. However, hosts SHOULD NOT return 0 from this function in non-exceptional circumstances (e.g. the URI map SHOULD be dynamic). Hosts that statically support only a fixed set of URIs should not expect plugins to function correctly.