}
	// Test error after ReadByte.
	_, _, err = r.ReadRune() // reset state
	if err != nil {
		t.Error("unexpected error on ReadRune (2):", err)
	}
	for range buf {
		_, err = r.ReadByte()
		if err != nil {
			t.Error("unexpected error on ReadByte (2):", err)
		}
	}
	if r.UnreadRune() == nil {
		t.Error("expected error after ReadByte")
	}
	// Test error after UnreadByte.

	n = copy(b, r.s[off:])
	if n < len(b) {
		err = io.EOF
	}
	return
}

// ReadByte implements the [io.ByteReader] interface.
func (r *Reader) ReadByte() (byte, error) {
	r.prevRune = -1
	if r.i >= int64(len(r.s)) {
		return 0, io.EOF
	}
	b := r.s[r.i]
	r.i++
	return b, nil
}

// UnreadByte complements [Reader.ReadByte] in implementing the [io.ByteScanner] interface.
func (r *Reader) UnreadByte() error {

		cr.err = errMalformedEncoding
		return n, cr.err
	}
	b, err := cr.reader.ReadByte()
	if err == io.EOF {
		err = io.ErrUnexpectedEOF
	}
	if err != nil {
		cr.err = err
		return n, cr.err
	}
	if b != '\r' {
		cr.err = errMalformedEncoding
		return n, cr.err
	}
	b, err = cr.reader.ReadByte()
	if err == io.EOF {
		err = io.ErrUnexpectedEOF
	}
	if err != nil {
		cr.err = err

    // Disable the timeout to read the first byte of a new frame.
    val b0: Int
    val timeoutBefore = source.timeout().timeoutNanos()
    source.timeout().clearTimeout()
    try {
      b0 = source.readByte() and 0xff
    } finally {
      source.timeout().timeout(timeoutBefore, TimeUnit.NANOSECONDS)
    }

    opcode = b0 and B0_MASK_OPCODE
    isFinalFrame = b0 and B0_FLAG_FIN != 0

    val length = source.readMedium()
    if (length > INITIAL_MAX_FRAME_SIZE) {
      throw IOException("FRAME_SIZE_ERROR: $length")
    }
    val type = source.readByte() and 0xff
    val flags = source.readByte() and 0xff
    val streamId = source.readInt() and 0x7fffffff // Ignore reserved bit.
    if (type != TYPE_WINDOW_UPDATE && logger.isLoggable(FINE)) {

    val sourceCodePoint1 =
      when (select(optionsDot)) {
        DELIMITER_DOT -> {
          if (readByte() != '.'.code.toByte()) throw IOException("expected '..'")
          readHexadecimalUnsignedLong()
        }

        else -> sourceCodePoint0
      }

    skipWhitespace()
    if (readByte() != ';'.code.toByte()) throw IOException("expected ';'")

    // "valid" or "mapped"
    skipWhitespace()

  writeByte(medium.ushr(8) and 0xff)
  writeByte(medium and 0xff)
}

@Throws(IOException::class)
internal fun BufferedSource.readMedium(): Int =
  (
    readByte() and 0xff shl 16
      or (readByte() and 0xff shl 8)
      or (readByte() and 0xff)
  )

/** Run [block] until it either throws an [IOException] or completes. */
internal inline fun ignoreIoExceptions(block: () -> Unit) {
  try {
    block()

  @Test
  fun sourceSeesBom() {
    val body = "efbbbf68656c6c6f".decodeHex().toResponseBody()
    val source = body.source()
    assertThat(source.readByte() and 0xff).isEqualTo(0xef)
    assertThat(source.readByte() and 0xff).isEqualTo(0xbb)
    assertThat(source.readByte() and 0xff).isEqualTo(0xbf)
    assertThat(source.readUtf8()).isEqualTo("hello")
  }

  @Test
  fun bytesEmpty() {
    val body = body("")

    in.readFully(b);
    assertEquals(-100, b[0]);
    assertEquals(100, b[1]);
    assertEquals(true, in.readBoolean());
    assertEquals(false, in.readBoolean());
    assertEquals(100, in.readByte());
    assertEquals(-100, in.readByte());
    assertEquals(200, in.readUnsignedByte());
    assertEquals('\u6100', in.readChar());
    assertEquals(-12150, in.readShort());
    assertEquals(20675, in.readUnsignedShort());

  @Override
  int skipBytes(int n);

  @CanIgnoreReturnValue // to skip a byte
  @Override
  boolean readBoolean();

  @CanIgnoreReturnValue // to skip a byte
  @Override
  byte readByte();

  @CanIgnoreReturnValue // to skip a byte
  @Override
  int readUnsignedByte();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  short readShort();