}

    // 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) {

    } else {
      // count how many bytes we'll need to express the length.
      val lengthBitCount = 64 - java.lang.Long.numberOfLeadingZeros(length)
      val lengthByteCount = (lengthBitCount + 7) / 8
      sink.writeByte(0b1000_0000 or lengthByteCount)
      for (shift in (lengthByteCount - 1) * 8 downTo 0 step 8) {
        sink.writeByte((length shr shift).toInt())
      }
    }

    // Write the payload.
    sink.writeAll(content)
  }

  override fun toString(): String = "$tagClass/$tag"

  companion object {
    const val TAG_CLASS_UNIVERSAL = 0b0000_0000
    const val TAG_CLASS_APPLICATION = 0b0100_0000
    const val TAG_CLASS_CONTEXT_SPECIFIC = 0b1000_0000
    const val TAG_CLASS_PRIVATE = 0b1100_0000

    const val TAG_END_OF_CONTENTS = 0L
  }

		// pointer to the scalarOrder field because comparing generic and
		// instantiated types is not supported.
		if &c.scalarOrder[0] == &p521Order[0] {
			key[0] &= 0b0000_0001
		}

		// In tests, rand will return all zeros and NewPrivateKey will reject
		// the zero key as it generates the identity as a public key. This also
		// makes this function consistent with crypto/elliptic.GenerateKey.

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
}