assertEquals(20, counter.getCount());
  }

  @SuppressWarnings("CheckReturnValue") // calling read() to skip a byte
  public void testMark() throws Exception {
    assertTrue(counter.markSupported());
    assertEquals(10, counter.read(new byte[10]));
    assertEquals(10, counter.getCount());
    counter.mark(5);
    counter.read();
    assertEquals(11, counter.getCount());
    counter.reset();

    in.mark(readlimit);
    mark = count;
    // it's okay to mark even if mark isn't supported, as reset won't work
  }

  @Override
  public synchronized void reset() throws IOException {
    if (!in.markSupported()) {
      throw new IOException("Mark not supported");
    }
    if (mark == -1) {
      throw new IOException("Mark not set");
    }

    in.reset();
    count = mark;
  }

    assertEquals(20, counter.getCount());
  }

  @SuppressWarnings("CheckReturnValue") // calling read() to skip a byte
  public void testMark() throws Exception {
    assertTrue(counter.markSupported());
    assertEquals(10, counter.read(new byte[10]));
    assertEquals(10, counter.getCount());
    counter.mark(5);
    counter.read();
    assertEquals(11, counter.getCount());
    counter.reset();

    ByteSource source = newByteSource(0, 10);
    ByteSource joined = ByteSource.concat(source, source);
    assertEquals(20, joined.size());
    InputStream in = joined.openStream();
    assertFalse(in.markSupported());
    assertEquals(10, in.available());
    int total = 0;
    while (in.read() != -1) {
      total++;
    }
    assertEquals(0, in.available());
    assertEquals(20, total);
  }

    ByteSource source = newByteSource(0, 10);
    ByteSource joined = ByteSource.concat(source, source);
    assertEquals(20, joined.size());
    InputStream in = joined.openStream();
    assertFalse(in.markSupported());
    assertEquals(10, in.available());
    int total = 0;
    while (in.read() != -1) {
      total++;
    }
    assertEquals(0, in.available());
    assertEquals(20, total);
  }

  }

  public void testMarkAndReset() throws IOException {
    String string = "abcdefghijklmnopqrstuvwxyz";
    CharSequenceReader reader = new CharSequenceReader(string);
    assertTrue(reader.markSupported());

    assertEquals(string, readFully(reader));
    assertFullyRead(reader);

    // reset and read again
    reader.reset();
    assertEquals(string, readFully(reader));
    assertFullyRead(reader);

    }
  }

  @Override
  public int available() throws IOException {
    if (in == null) {
      return 0;
    }
    return in.available();
  }

  @Override
  public boolean markSupported() {
    return false;
  }

  @Override
  public int read() throws IOException {
    while (in != null) {
      int result = in.read();
      if (result != -1) {
        return result;
      }

    }
    return numOfBytesRead;
  }

  /**
   * mark() is not supported for HashingInputStream
   *
   * @return {@code false} always
   */
  @Override
  public boolean markSupported() {
    return false;
  }

  /** mark() is not supported for HashingInputStream */
  @Override
  public void mark(int readlimit) {}

  /**
   * reset() is not supported for HashingInputStream.
   *

    return charsToSkip;
  }

  @Override
  public synchronized boolean ready() throws IOException {
    checkOpen();
    return true;
  }

  @Override
  public boolean markSupported() {
    return true;
  }

  @Override
  public synchronized void mark(int readAheadLimit) throws IOException {
    checkArgument(readAheadLimit >= 0, "readAheadLimit (%s) may not be negative", readAheadLimit);

  }

  public void testMarkAndReset() throws IOException {
    String string = "abcdefghijklmnopqrstuvwxyz";
    CharSequenceReader reader = new CharSequenceReader(string);
    assertTrue(reader.markSupported());

    assertEquals(string, readFully(reader));
    assertFullyRead(reader);

    // reset and read again
    reader.reset();
    assertEquals(string, readFully(reader));
    assertFullyRead(reader);