Function getoption

third-party/lua-5.5.0/src/lstrlib.c:1492–1533

** Read and classify next option. 'size' is filled with option's size. */

** Read and classify next option. 'size' is filled with option's size.
*/
static KOption getoption (Header *h, const char **fmt, size_t *size) {
  /* dummy structure to get native alignment requirements */
  struct cD { char c; union { LUAI_MAXALIGN; } u; };
  int opt = *((*fmt)++);
  *size = 0;  /* default */
  switch (opt) {
    case 'b': *size = sizeof(char); return Kint;
    case 'B': *size = sizeof(char); return Kuint;
    case 'h': *size = sizeof(short); return Kint;
    case 'H': *size = sizeof(short); return Kuint;
    case 'l': *size = sizeof(long); return Kint;
    case 'L': *size = sizeof(long); return Kuint;
    case 'j': *size = sizeof(lua_Integer); return Kint;
    case 'J': *size = sizeof(lua_Integer); return Kuint;
    case 'T': *size = sizeof(size_t); return Kuint;
    case 'f': *size = sizeof(float); return Kfloat;
    case 'n': *size = sizeof(lua_Number); return Knumber;
    case 'd': *size = sizeof(double); return Kdouble;
    case 'i': *size = getnumlimit(h, fmt, sizeof(int)); return Kint;
    case 'I': *size = getnumlimit(h, fmt, sizeof(int)); return Kuint;
    case 's': *size = getnumlimit(h, fmt, sizeof(size_t)); return Kstring;
    case 'c':
      *size = getnum(fmt, cast_sizet(-1));
      if (l_unlikely(*size == cast_sizet(-1)))
        luaL_error(h->L, "missing size for format option 'c'");
      return Kchar;
    case 'z': return Kzstr;
    case 'x': *size = 1; return Kpadding;
    case 'X': return Kpaddalign;
    case ' ': break;
    case '<': h->islittle = 1; break;
    case '>': h->islittle = 0; break;
    case '=': h->islittle = nativeendian.little; break;
    case '!': {
      const size_t maxalign = offsetof(struct cD, u);
      h->maxalign = getnumlimit(h, fmt, maxalign);
      break;
    }
    default: luaL_error(h->L, "invalid format option '%c'", opt);
  }
  return Knop;
}


/*