bmp__add_character_range Subroutine

   pure subroutine bmp__add_character_range(self, min_cp, max_cp)
      implicit none
      class(bmp_t), intent(inout) :: self
      integer(int32), intent(in) :: min_cp, max_cp
      
      integer :: ib, ie ! (array) index begin, index end
      integer :: pb, pe ! (bit) position begin, position end
      integer :: i
      integer(int64) :: c1, c2

      if (min_cp > max_cp) return
      if (min_cp > BMP_SIZE_BIT) return
      if (min_cp == max_cp) then
         call bmp__add_character_codepoint(self, min_cp)
         return
      end if

      ib = min_cp / bits_64
      ie = min( max_cp/bits_64, BMP_SIZE-1)

      pb = mod(min_cp, bits_64)
      if (max_cp > BMP_SIZE_BIT) then
         pe = 64
      else
         pe = mod(max_cp, bits_64)
      end if

      if (ib > BMP_SIZE-1) return

      c1 = self%b(ib)
      c2 = self%b(ie)

      if (ib == ie) then
         ! Set bits in the range min to max.
         self%b(ib) = ior(c1, shiftl( (ishft(1_8, pe - pb + 1) - 1), pb))
      else
         ! First integer: set pb to 63
         self%b(ib) = ior(c1, shiftl(not(0_int64), pb))

         ! The integers between have all bits set to 1.
         do concurrent (i = ib+1:ie-1)
            self%b(i) = -1_int64
         end do

         ! Last integer: set bits from 0 to pe.
         self%b(ie) = ior(c2, (ishft(1_int64, pe+1)-1))
      end if

   end subroutine bmp__add_character_range