// considered read operations.
func (b *Reader) UnreadByte() error {
	if b.lastByte < 0 || b.r == 0 && b.w > 0 {
		return ErrInvalidUnreadByte
	}
	// b.r > 0 || b.w == 0
	if b.r > 0 {
		b.r--
	} else {
		// b.r == 0 && b.w == 0
		b.w = 1
	}
	b.buf[b.r] = byte(b.lastByte)
	b.lastByte = -1
	b.lastRuneSize = -1
	return nil
}

  @Param({"1000", "100000"})
  private int size;

  @Param WhereToDiffer whereToDiffer;

  @Param EqualsImplementation equalsImpl;

  private enum WhereToDiffer {
    ONE_PERCENT_IN,
    LAST_BYTE,
    NOT_AT_ALL;
  }

  private enum EqualsImplementation {
    ANDING_BOOLEANS {
      @Override
      boolean doEquals(byte[] a, byte[] b) {
        if (a.length != b.length) {
          return false;

  @Param({"1000", "100000"})
  private int size;

  @Param WhereToDiffer whereToDiffer;

  @Param EqualsImplementation equalsImpl;

  private enum WhereToDiffer {
    ONE_PERCENT_IN,
    LAST_BYTE,
    NOT_AT_ALL;
  }

  private enum EqualsImplementation {
    ANDING_BOOLEANS {
      @Override
      boolean doEquals(byte[] a, byte[] b) {
        if (a.length != b.length) {
          return false;