BLO_core_bhead.hh

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/* SPDX-FileCopyrightText: 2025 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#pragma once
 
#include <optional>
 
#include "BLI_endian_switch.h"
#include "BLI_sys_types.h"
 
struct FileReader;
 
struct BHead {
  int code;
  int SDNAnr;
  const void *old;
  int64_t len;
  int64_t nr;
};
 
struct BHead4 {
  int code, len;
  uint old;
  int SDNAnr, nr;
};
 
struct SmallBHead8 {
  int code, len;
  uint64_t old;
  int SDNAnr, nr;
};
 
struct LargeBHead8 {
  int code;
  int SDNAnr;
  uint64_t old;
  int64_t len;
  int64_t nr;
};
 
enum class BHeadType {
  BHead4,
  SmallBHead8,
  LargeBHead8,
};

#ifdef __BIG_ENDIAN__
/* Big Endian */
#  define BLEND_MAKE_ID(a, b, c, d) ((int)(a) << 24 | (int)(b) << 16 | (c) << 8 | (d))
#else
/* Little Endian */
#  define BLEND_MAKE_ID(a, b, c, d) ((int)(d) << 24 | (int)(c) << 16 | (b) << 8 | (a))
#endif

enum {
  BLO_CODE_DATA = BLEND_MAKE_ID('D', 'A', 'T', 'A'),
  BLO_CODE_GLOB = BLEND_MAKE_ID('G', 'L', 'O', 'B'),
  BLO_CODE_DNA1 = BLEND_MAKE_ID('D', 'N', 'A', '1'),
  BLO_CODE_TEST = BLEND_MAKE_ID('T', 'E', 'S', 'T'),
  BLO_CODE_REND = BLEND_MAKE_ID('R', 'E', 'N', 'D'),
  BLO_CODE_USER = BLEND_MAKE_ID('U', 'S', 'E', 'R'),
  BLO_CODE_ENDB = BLEND_MAKE_ID('E', 'N', 'D', 'B'),
};

std::optional<BHead> BLO_readfile_read_bhead(FileReader *file, BHeadType type);

inline uint32_t uint32_from_uint64_ptr(uint64_t ptr)
{
  /* NOTE: this is endianness-sensitive. */
  /* Switching endianness would be required to reduce the risk of two different 64bits pointers
   * generating the same 32bits value. */
  /* Behavior has to match #cast_pointer_64_to_32. */
  ptr >>= 3;
  return uint32_t(ptr);
}