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diff --git a/ext/uri-map.lv2/uri-map.h b/ext/uri-map.lv2/uri-map.h
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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 */
+