T BitWriter
   FileWr out
   accumulator = 0
   bcount = 0

   F (fname)
      .out = File(fname, WRITE)

   F _writebit(bit)
      I .bcount == 8
         .flush()
      I bit > 0
         .accumulator [|]= 1 << (7 - .bcount)
      .bcount++

   F writebits(bits, =n)
      L n > 0
         ._writebit(bits [&] 1 << (n - 1))
         n--

   F flush()
      .out.write_bytes([Byte(.accumulator)])
      .accumulator = 0
      .bcount = 0

   F close()
      .flush()
      .out.close()

T BitReader
   File input
   accumulator = 0
   bcount = 0
   read = 0

   F (fname)
      .input = File(fname)

   F _readbit()
      I .bcount == 0
         V a = .input.read_bytes(at_most' 1)
         I !a.empty
            .accumulator = a[0]
         .bcount = 8
         .read = a.len
      V rv = (.accumulator [&] (1 << (.bcount - 1))) >> (.bcount - 1)
      .bcount--
      R rv

   F readbits(=n)
      V v = 0
      L n > 0
         v = (v << 1) [|] ._readbit()
         n--
      R v

V writer = BitWriter(‘bitio_test.dat’)
V chars = ‘12345abcde’
L(ch) chars
   writer.writebits(ch.code, 7)
writer.close()

V reader = BitReader(‘bitio_test.dat’)
[Char] charsa
L
   V x = reader.readbits(7)
   I reader.read == 0
      L.break
   charsa.append(Char(code' x))
print(charsa.join(‘’))