Function fieldargs

third-party/lua-5.2.4/src/lbitlib.c:155–164

** get field and width arguments for field-manipulation functions, ** checking whether they are valid. ** ('luaL_error' called without 'return' to avoid later warnings about ** 'width' being used uninitialized.) */

** 'width' being used uninitialized.)
*/
static int fieldargs (lua_State *L, int farg, int *width) {
  int f = luaL_checkint(L, farg);
  int w = luaL_optint(L, farg + 1, 1);
  luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
  luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
  if (f + w > LUA_NBITS)
    luaL_error(L, "trying to access non-existent bits");
  *width = w;
  return f;
}


static int b_extract (lua_State *L) {