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/* lv2_uri_map.h - C header file for the LV2 URI Map extension.
*
* Copyright (C) 2008-2009 David Robillard <http://drobilla.net>
*
* 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 header for the LV2 URI Map extension <http://lv2plug.in/ns/ext/uri-map>.
*
* This extension defines a simple mechanism for plugins to map URIs to
* integers, usually for performance reasons (e.g. processing events
* typed by URIs in real time). The expected use case is for plugins to
* map URIs to integers for things they 'understand' at instantiation time,
* and store those values for use in the audio thread without doing any string
* comparison. This allows the extensibility of RDF with the performance of
* integers (or centrally defined enumerations).
*/
#ifndef LV2_URI_MAP_H
#define LV2_URI_MAP_H
#define LV2_URI_MAP_URI "http://lv2plug.in/ns/ext/uri-map"
#include <stdint.h>
/** Opaque pointer to host data. */
typedef void* LV2_URI_Map_Callback_Data;
/** The data field of the LV2_Feature for this extension.
*
* 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.
*/
typedef struct {
/** 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.
*/
LV2_URI_Map_Callback_Data callback_data;
/** Get the numeric ID of a URI from the host.
*
* @param callback_data Must be the callback_data member of this struct.
* @param 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.
* @param 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 means an ID for that URI could not
* be created for whatever reason. Extensions may define more precisely
* what this means, but in general plugins should gracefully handle 0
* and consider whatever they wanted the URI for "unsupported".
*/
uint32_t (*uri_to_id)(LV2_URI_Map_Callback_Data callback_data,
const char* map,
const char* uri);
} LV2_URI_Map_Feature;
#endif /* LV2_URI_MAP_H */
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