{FloatLit, "0x1234PAB", "0x1234P AB", "exponent has no digits"},
		{FloatLit, "0x1.2p1a", "0x1.2p1 a", ""},

		{ImagLit, "0xf00.bap+12i", "0xf00.bap+12i", ""},

		// separators
		{IntLit, "0b_1000_0001", "0b_1000_0001", ""},
		{IntLit, "0o_600", "0o_600", ""},
		{IntLit, "0_466", "0_466", ""},
		{IntLit, "1_000", "1_000", ""},
		{FloatLit, "1_000.000_1", "1_000.000_1", ""},
		{ImagLit, "10e+1_2_3i", "10e+1_2_3i", ""},

		{Float, "0xeP-", "0xeP-", "exponent has no digits"},
		{Float, "0x1234PAB", "0x1234P AB", "exponent has no digits"},
		{Float, "0x1.2p1a", "0x1.2p1 a", ""},

		// separators
		{Int, "0b_1000_0001", "0b_1000_0001", ""},
		{Int, "0o_600", "0o_600", ""},
		{Int, "0_466", "0_466", ""},
		{Int, "1_000", "1_000", ""},
		{Float, "1_000.000_1", "1_000.000_1", ""},
		{Int, "0x_f00d", "0x_f00d", ""},

		{token.FLOAT, "0x1.2p1a", "0x1.2p1 a", ""},

		{token.IMAG, "0xf00.bap+12i", "0xf00.bap+12i", ""},

		// separators
		{token.INT, "0b_1000_0001", "0b_1000_0001", ""},
		{token.INT, "0o_600", "0o_600", ""},
		{token.INT, "0_466", "0_466", ""},
		{token.INT, "1_000", "1_000", ""},
		{token.FLOAT, "1_000.000_1", "1_000.000_1", ""},

      }

    // Read the length.
    val length0 = source.readByte().toInt() and 0xff
    val length =
      when {
        length0 == 0b1000_0000 -> {
          throw ProtocolException("indefinite length not permitted for DER")
        }
        (length0 and 0b1000_0000) == 0b1000_0000 -> {
          // Length specified over multiple bytes.
          val lengthBytes = length0 and 0b0111_1111
          if (lengthBytes > 8) {

	{"1_000", 0, false, nat{1000}, 10, 4, nil, 0},
	{"0_466", 0, false, nat{0466}, 8, 3, nil, 0},
	{"0o_600", 0, false, nat{0600}, 8, 3, nil, 0},
	{"0x_f0_0d", 0, false, nat{0xf00d}, 16, 4, nil, 0},
	{"0b1000_0001", 0, false, nat{0x81}, 2, 8, nil, 0},
	{"1_000.000_1", 0, true, nat{10000001}, 10, -4, nil, 0},
	{"0x_f00d.1e", 0, true, nat{0xf00d1e}, 16, -2, nil, 0},
	{"0x_f00d.1E2", 0, true, nat{0xf00d1e2}, 16, -3, nil, 0},

import org.junit.jupiter.api.Test

internal class DerTest {
  @Test fun `decode tag and length`() {
    val buffer =
      Buffer()
        .writeByte(0b00011110)
        .writeByte(0b10000001)
        .writeByte(0b11001001)

    val derReader = DerReader(buffer)

    derReader.read("test") { header ->
      assertThat(header.tagClass).isEqualTo(DerHeader.TAG_CLASS_UNIVERSAL)

			}
		}
	}
}

func BitRev7(n uint8) uint8 {
	if n>>7 != 0 {
		panic("not 7 bits")
	}
	var r uint8
	r |= n >> 6 & 0b0000_0001
	r |= n >> 4 & 0b0000_0010
	r |= n >> 2 & 0b0000_0100
	r |= n /**/ & 0b0000_1000
	r |= n << 2 & 0b0001_0000
	r |= n << 4 & 0b0010_0000
	r |= n << 6 & 0b0100_0000
	return r
}