protobuf/upb/extension_registry.h

/*
 * Copyright (c) 2009-2021, Google LLC
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name of Google LLC nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 Google LLC 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 UPB_EXTENSION_REGISTRY_H_
#define UPB_EXTENSION_REGISTRY_H_

#include <stddef.h>

#include "upb/upb.h"

#ifdef __cplusplus
extern "C" {
#endif

/* Extension registry: a dynamic data structure that stores a map of:
 *   (upb_MiniTable, number) -> extension info
 *
 * upb_decode() uses upb_ExtensionRegistry to look up extensions while parsing
 * binary format.
 *
 * upb_ExtensionRegistry is part of the mini-table (msglayout) family of
 * objects. Like all mini-table objects, it is suitable for reflection-less
 * builds that do not want to expose names into the binary.
 *
 * Unlike most mini-table types, upb_ExtensionRegistry requires dynamic memory
 * allocation and dynamic initialization:
 * * If reflection is being used, then upb_DefPool will construct an appropriate
 *   upb_ExtensionRegistry automatically.
 * * For a mini-table only build, the user must manually construct the
 *   upb_ExtensionRegistry and populate it with all of the extensions the user
 * cares about.
 * * A third alternative is to manually unpack relevant extensions after the
 *   main parse is complete, similar to how Any works. This is perhaps the
 *   nicest solution from the perspective of reducing dependencies, avoiding
 *   dynamic memory allocation, and avoiding the need to parse uninteresting
 *   extensions.  The downsides are:
 *     (1) parse errors are not caught during the main parse
 *     (2) the CPU hit of parsing comes during access, which could cause an
 *         undesirable stutter in application performance.
 *
 * Users cannot directly get or put into this map. Users can only add the
 * extensions from a generated module and pass the extension registry to the
 * binary decoder.
 *
 * A upb_DefPool provides a upb_ExtensionRegistry, so any users who use
 * reflection do not need to populate a upb_ExtensionRegistry directly.
 */

struct upb_ExtensionRegistry;
typedef struct upb_ExtensionRegistry upb_ExtensionRegistry;

/* Creates a upb_ExtensionRegistry in the given arena.  The arena must outlive
 * any use of the extreg. */
upb_ExtensionRegistry* upb_ExtensionRegistry_New(upb_Arena* arena);

#ifdef __cplusplus
} /* extern "C" */
#endif

#endif /* UPB_EXTENSION_REGISTRY_H_ */