Function posrelatI

3rd/lua-5.4.3/src/lstrlib.c:71–79

** translate a relative initial string position ** (negative means back from end): clip result to [1, inf). ** The length of any string in Lua must fit in a lua_Integer, ** so there are no overflows in the casts. ** The inverted comparison avoids a possible overflow ** computing '-pos'. */

** computing '-pos'.
*/
static size_t posrelatI (lua_Integer pos, size_t len) {
  if (pos > 0)
    return (size_t)pos;
  else if (pos == 0)
    return 1;
  else if (pos < -(lua_Integer)len)  /* inverted comparison */
    return 1;  /* clip to 1 */
  else return len + (size_t)pos + 1;
}


/*