lua5.3 support load x32 bytecode on x64

lundump_lua53_load_x32_bytecode_on_x64.c

typedef struct {
  lua_State *L;
  ZIO *Z;
  Mbuffer *b;
  const char *name;

  lu_byte load_size_t_size;
  lu_byte load_size_t_offset;
} LoadState;

typedef union {
  lua_Integer a;
  lu_byte b[sizeof(lua_Integer)];
} IntOrBytes;

#define ST_SIZE sizeof(size_t)

/* ... */

static size_t LoadSize(LoadState* S) {
  union {
    lu_byte b[ST_SIZE];
    size_t sz;
  } v;

  memset(&v, 0, sizeof(v));
  LoadBlock(S, &v.b[S->load_size_t_offset], S->load_size_t_size);
  return v.sz;
}

static TString *LoadString (LoadState *S) {
  size_t size = LoadByte(S);
  if (size == 0xFF) {
    /* LoadVar(S, size); */
    size = LoadSize(S);
  }
  if (size == 0)
    return NULL;
  else {
    char *s = luaZ_openspace(S->L, S->b, --size);
    LoadVector(S, s, size);
    return luaS_newlstr(S->L, s, size);
  }
}

/* ... */

static void checkHeader (LoadState *S) {
  checkliteral(S, LUA_SIGNATURE + 1, "not a");  /* 1st char already checked */
  if (LoadByte(S) != LUAC_VERSION)
    error(S, "version mismatch in");
  if (LoadByte(S) != LUAC_FORMAT)
    error(S, "format mismatch in");
  checkliteral(S, LUAC_DATA, "corrupted");
  checksize(S, int);

  /* supprt run x32 bytes on x64 arch */
  /* checksize(S, size_t); */
  S->load_size_t_size = LoadByte(S);

  checksize(S, Instruction);
  checksize(S, lua_Integer);
  checksize(S, lua_Number);

  /* supprt run x32 bytes on x64 arch */
  IntOrBytes i = (IntOrBytes)LoadInteger(S);
  lu_byte b = (lu_byte)LUAC_INT;
  int is_little_endian = (i.b[0] == b) ? 1 : 0;
  S->load_size_t_offset = is_little_endian ? 0 : (ST_SIZE - S->load_size_t_size);

  if (i.a != LUAC_INT)
    error(S, "endianness mismatch in");
  if (LoadNumber(S) != LUAC_NUM)
    error(S, "float format mismatch in");
}