cube__first_codepoint Function

   pure function cube__first_codepoint(self) result(ret)
      use :: forgex_parameters_m, only: UTF8_CODE_MAX
      implicit none
      class(cube_t), intent(in) :: self

      integer :: i, num, pos, ret, candi

      if (.not. self%is_switched_to_bmp) then
         do i = 0, ASCII_SIZE-1
            if (self%ascii%a(i) /= 0) then
               pos = trailz(self%ascii%a(i))
               ret = i*bits_64+pos
               return
            end if
         end do
         ret = INVALID_CODE_POINT
         return
      end if

      do i = 0, BMP_SIZE-1
         if (self%bmp%b(i) /= 0) then
            pos = trailz(self%bmp%b(i))
            ret = i*bits_64 + pos
            return
         end if
      end do

      ret = INVALID_CODE_POINT
      if (.not. allocated(self%sps)) return

      candi = UTF8_CODE_MAX
      do i = 1, size(self%sps)
         candi = min(candi, self%sps(i)%min)
      end do

      if (candi /= UTF8_CODE_MAX) then
         ret = candi
      else
         ret = -1
      end if

   end function cube__first_codepoint