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+/* Dynamic manifest specification for LV2
+ * Revision 1
+ *
+ * Copyright (C) 2008, 2009 Stefano D'Angelo <zanga.mail@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef LV2_DYN_MANIFEST_H_INCLUDED
+#define LV2_DYN_MANIFEST_H_INCLUDED
+
+#include <stdio.h>
+#include "lv2.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/* ************************************************************************* */
+
+
+/** @file
+ * C header for the LV2 Dynamic Manifest extension
+ * <http://lv2plug.in/ns/ext/dyn-manifest>.
+ * Revision: 1
+ *
+ * == Overview ==
+ *
+ * The LV2 API, on its own, cannot be used to write plugin libraries where
+ * data is dynamically generated at runtime (e.g. API wrappers), since LV2
+ * requires needed information to be provided in one or more static data (RDF)
+ * files. This API addresses this limitation by extending the LV2 API.
+ *
+ * A host implementing support for this API should first detect that the plugin
+ * library implements a dynamic manifest generator by examining its static
+ * manifest file, then fetch data from the shared object file by accessing it as
+ * usual (dlopen() and family) and using this API.
+ *
+ * The host is allowed to request regeneration of the dynamic manifest multiple
+ * times, and the plugin library is expected to provide updated data if/when
+ * possible. All data and references provided via this API before the last
+ * regeneration of the dynamic manifest is to be considered invalid by the
+ * host, including plugin descriptors whose URIs were discovered using this API.
+ *
+ * This API is extensible in a similar fashion as the LV2 plugin API.
+ *
+ * == Threading rules ==
+ *
+ * This specification defines threading rule classes, similarly to the LV2
+ * specification.
+ *
+ * The functions defined by this API belong to:
+ *
+ * - Dynamic manifest open class: lv2_dyn_manifest_open()
+ * - Dynamic manifest close class: lv2_dyn_manifest_close()
+ * - Dynamic manifest file class: lv2_dyn_manifest_get_subjects(),
+ * lv2_dyn_manifest_get_data()
+ *
+ * The rules that hosts must follow are these:
+ *
+ * - When a function from the Dynamic manifest open or the Dynamic manifest
+ * close class is running, no other functions in the same shared object file
+ * may run.
+ * - When a function from the Dynamic manifest file class is called, no other
+ * functions from the same class may run if they are given at least one
+ * FILE * argument with the same value.
+ * - A function from the Dynamic manifest open class may not run after a
+ * successful call to a function from the same class, in case a function from
+ * the Dynamic manifest close class was not successfully called in the
+ * meanwhile.
+ * - A function from the Dynamic manifest close class may only run after a
+ * successful call to a function from the Dynamic manifest open class.
+ * - A function from the Dynamic manifest file class may only run beetween a
+ * successful call to a function from the Dynamic manifest open class and the
+ * following successful call to a function from the Dynamic manifest close
+ * class.
+ *
+ * Extensions to this specification which add new functions MUST declare in
+ * which of these classes the functions belong, or define new classes for them;
+ * furthermore, classes defined by such extensions MUST only allow calls after
+ * a successful call to a function from the Dynamic manifest open class and
+ * before the following successful call to a function from the Dynamic manifest
+ * close class.
+ *
+ * Any simultaneous calls that are not explicitly forbidden by these rules are
+ * allowed.
+ */
+
+
+/* ************************************************************************* */
+
+
+/** Dynamic manifest generator handle.
+ *
+ * This handle indicates a particular status of a dynamic manifest generator.
+ * The host MUST NOT attempt to interpret it and, unlikely LV2_Handle, it is NOT
+ * even valid to compare this to NULL. The dynamic manifest generator may use it
+ * to reference internal data. */
+typedef void * LV2_Dyn_Manifest_Handle;
+
+
+/* ************************************************************************* */
+
+
+/** Accessing data.
+ *
+ * Whenever a host wants to access data using this API, it could:
+ *
+ * 1. Call lv2_dyn_manifest_open();
+ * 2. Create an empty resource identified by a FILE *;
+ * 3. Get a "list" of exposed subject URIs using
+ * lv2_dyn_manifest_get_subjects();
+ * 4. Call lv2_dyn_manifest_get_data() for each URI of interest, in order to
+ * get data related to that URI (either by calling the function subsequently
+ * with the same FILE * resource, or by creating more FILE * resources to
+ * perform parallel calls);
+ * 5. Call lv2_dyn_manifest_close();
+ * 6. Parse the content of the FILE * resource(s).
+ * 7. Free/delete/unlink the FILE * resource(s).
+ *
+ * The content of the FILE * resources has to be interpreted by the host as a
+ * regular file in Turtle syntax. This also means that each FILE * resource
+ * should also contain needed prefix definitions, in case any are used.
+ *
+ * Each call to lv2_dyn_manifest_open() automatically implies the (re)generation
+ * of the dynamic manifest on the library side.
+ *
+ * When such calls are made, data fetched from the involved library using this
+ * API before such call is to be considered no more valid.
+ *
+ * In case the library uses this same API to access other dynamic manifests, it
+ * MUST implement some mechanism to avoid potentially endless loops (such as A
+ * loads B, B loads A, etc.) in functions from the Dynamic manifest open class
+ * (the open-like operation MUST fail). For this purpose, use of a static
+ * boolean flag is suggested.
+ */
+
+/** Function that (re)generates the dynamic manifest.
+ *
+ * handle is a pointer to an uninitialized dynamic manifest generator handle.
+ *
+ * features is a NULL terminated array of LV2_Feature structs which
+ * represent the features the host supports. The dynamic manifest geenrator may
+ * refuse to (re)generate the dynamic manifest if required features are not
+ * found here (however hosts SHOULD NOT use this as a discovery mechanism,
+ * instead of reading the static manifest file). This array must always exist;
+ * if a host has no features, it MUST pass a single element array containing
+ * NULL.
+ *
+ * This function MUST return 0 on success, otherwise a non-zero error code, and
+ * the host SHOULD evaluate the result of the operation by examining the
+ * returned value, rather than try to interpret the value of handle.
+ */
+int lv2_dyn_manifest_open(LV2_Dyn_Manifest_Handle * handle,
+ const LV2_Feature *const * features);
+
+/** Function that fetches a "list" of subject URIs exposed by the dynamic
+ * manifest generator.
+ *
+ * handle is the dynamic manifest generator handle.
+ *
+ * fp is the FILE * identifying the resource the host has to set up for the
+ * dynamic manifest generator. The host MUST pass a writable, empty resource to
+ * this function, and the dynamic manifest generator MUST ONLY perform write
+ * operations on it at the end of the stream (e.g. use only fprintf(), fwrite()
+ * and similar).
+ *
+ * The dynamic manifest generator has to fill the resource only with the needed
+ * triples to make the host aware of the "objects" it wants to expose. For
+ * example, if the library exposes a regular LV2 plugin, it should output only a
+ * triple like the following:
+ *
+ * <http://www.example.com/plugin/uri> a lv2:Plugin;
+ *
+ * This function MUST return 0 on success, otherwise a non-zero error code.
+ */
+int lv2_dyn_manifest_get_subjects(LV2_Dyn_Manifest_Handle handle,
+ FILE * fp);
+
+/** Function that fetches data related to a specific URI.
+ *
+ * handle is the dynamic manifest generator handle.
+ *
+ * fp is the FILE * identifying the resource the host has to set up for the
+ * dynamic manifest generator. The host MUST pass a writable resource to this
+ * function, and the dynamic manifest generator MUST ONLY perform write
+ * operations on it at the current position of the stream (e.g. use only
+ * fprintf(), fwrite() and similar).
+ *
+ * uri is the URI to get data about (in the "plain" form, a.k.a. without RDF
+ * prefixes).
+ *
+ * The dynamic manifest generator has to fill the resource with data related to
+ * the URI. For example, if the library exposes a regular LV2 plugin whose URI,
+ * as retrieved by the host using lv2_dyn_manifest_get_subjects() is
+ * http://www.example.com/plugin/uri, it should output something like:
+ *
+ * <http://www.example.com/plugin/uri> a lv2:Plugin;
+ * lv2:binary <mylib.so>;
+ * doap:name "My Plugin";
+ * ... etc...
+ *
+ * This function MUST return 0 on success, otherwise a non-zero error code.
+ */
+int lv2_dyn_manifest_get_data(LV2_Dyn_Manifest_Handle handle,
+ FILE * fp,
+ const char * uri);
+
+/** Function that ends the operations on the dynamic manifest generator.
+ *
+ * handle is the dynamic manifest generator handle.
+ *
+ * This function should be used by the dynamic manifest generator to perform
+ * cleanup operations, etc.
+ */
+void lv2_dyn_manifest_close(LV2_Dyn_Manifest_Handle handle);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* LV2_DYN_MANIFEST_H_INCLUDED */
+