upb/mini_table/internal/message.h

// 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_INTERNAL_MESSAGE_H_
#define UPB_MINI_TABLE_INTERNAL_MESSAGE_H_

#include "upb/message/types.h"
#include "upb/mini_table/internal/field.h"

// Must be last.
#include "upb/port/def.inc"

struct upb_Decoder;
typedef const char* _upb_FieldParser(struct upb_Decoder* d, const char* ptr,
                                     upb_Message* msg, intptr_t table,
                                     uint64_t hasbits, uint64_t data);
typedef struct {
  uint64_t field_data;
  _upb_FieldParser* field_parser;
} _upb_FastTable_Entry;

typedef enum {
  kUpb_ExtMode_NonExtendable = 0,  // Non-extendable message.
  kUpb_ExtMode_Extendable = 1,     // Normal extendable message.
  kUpb_ExtMode_IsMessageSet = 2,   // MessageSet message.
  kUpb_ExtMode_IsMessageSet_ITEM =
      3,  // MessageSet item (temporary only, see decode.c)

  // During table building we steal a bit to indicate that the message is a map
  // entry.  *Only* used during table building!
  kUpb_ExtMode_IsMapEntry = 4,
} upb_ExtMode;

union upb_MiniTableSub;

// upb_MiniTable represents the memory layout of a given upb_MessageDef.
// The members are public so generated code can initialize them,
// but users MUST NOT directly read or write any of its members.
struct upb_MiniTable {
  const union upb_MiniTableSub* subs;
  const struct upb_MiniTableField* fields;

  // Must be aligned to sizeof(void*). Doesn't include internal members like
  // unknown fields, extension dict, pointer to msglayout, etc.
  uint16_t size;

  uint16_t field_count;
  uint8_t ext;  // upb_ExtMode, declared as uint8_t so sizeof(ext) == 1
  uint8_t dense_below;
  uint8_t table_mask;
  uint8_t required_count;  // Required fields have the lowest hasbits.

  // To statically initialize the tables of variable length, we need a flexible
  // array member, and we need to compile in gnu99 mode (constant initialization
  // of flexible array members is a GNU extension, not in C99 unfortunately.
  _upb_FastTable_Entry fasttable[];
};

#ifdef __cplusplus
extern "C" {
#endif

// A MiniTable for an empty message, used for unlinked sub-messages.
extern const struct upb_MiniTable _kUpb_MiniTable_Empty;

// Computes a bitmask in which the |l->required_count| lowest bits are set,
// except that we skip the lowest bit (because upb never uses hasbit 0).
//
// Sample output:
//    requiredmask(1) => 0b10 (0x2)
//    requiredmask(5) => 0b111110 (0x3e)
UPB_INLINE uint64_t upb_MiniTable_requiredmask(const struct upb_MiniTable* l) {
  int n = l->required_count;
  assert(0 < n && n <= 63);
  return ((1ULL << n) - 1) << 1;
}

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

#include "upb/port/undef.inc"

#endif /* UPB_MINI_TABLE_INTERNAL_MESSAGE_H_ */