extension_registry.h

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// Protocol Buffers - Google's data interchange format
// Copyright 2023 Google LLC.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
 
#ifndef UPB_MINI_TABLE_EXTENSION_REGISTRY_H_
#define UPB_MINI_TABLE_EXTENSION_REGISTRY_H_
 
#include <stddef.h>
#include <stdint.h>
 
#include "upb/mem/arena.h"
#include "upb/mini_table/extension.h"
#include "upb/mini_table/message.h"
 
// Must be last.
#include "upb/port/def.inc"
 
#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.
 */
 
typedef struct upb_ExtensionRegistry upb_ExtensionRegistry;
 
typedef enum {
  kUpb_ExtensionRegistryStatus_Ok = 0,
  kUpb_ExtensionRegistryStatus_DuplicateEntry = 1,
  kUpb_ExtensionRegistryStatus_OutOfMemory = 2,
  kUpb_ExtensionRegistryStatus_InvalidExtension = 3,
} upb_ExtensionRegistryStatus;
 
// Creates a upb_ExtensionRegistry in the given arena.
// The arena must outlive any use of the extreg.
UPB_API upb_ExtensionRegistry* upb_ExtensionRegistry_New(upb_Arena* arena);
 
UPB_API upb_ExtensionRegistryStatus upb_ExtensionRegistry_Add(
    upb_ExtensionRegistry* r, const upb_MiniTableExtension* e);
 
// Adds the given extension info for the array |e| of size |count| into the
// registry. If there are any errors, the entire array is backed out.
// The extensions must outlive the registry.
// Possible errors include OOM or an extension number that already exists.
upb_ExtensionRegistryStatus upb_ExtensionRegistry_AddArray(
    upb_ExtensionRegistry* r, const upb_MiniTableExtension** e, size_t count);
 
#ifdef UPB_LINKARR_DECLARE
 
// Adds all extensions linked into the binary into the registry.  The set of
// linked extensions is assembled by the linker using linker arrays.  This
// will likely not work properly if the extensions are split across multiple
// shared libraries.
//
// Returns true if all extensions were added successfully, false on out of
// memory or if any extensions were already present.
//
// This API is currently not available on MSVC (though it *is* available on
// Windows using clang-cl).
UPB_API bool upb_ExtensionRegistry_AddAllLinkedExtensions(
    upb_ExtensionRegistry* r);
 
#endif  // UPB_LINKARR_DECLARE
 
// Looks up the extension (if any) defined for message type |t| and field
// number |num|. Returns the extension if found, otherwise NULL.
UPB_API const upb_MiniTableExtension* upb_ExtensionRegistry_Lookup(
    const upb_ExtensionRegistry* r, const upb_MiniTable* t, uint32_t num);
 
#ifdef __cplusplus
} /* extern "C" */
#endif
 
#include "upb/port/undef.inc"
 
#endif /* UPB_MINI_TABLE_EXTENSION_REGISTRY_H_ */