/**
 * An {@link OutputStream} that maintains a hash of the data written to it.
 *
 * @author Nick Piepmeier
 * @since 16.0
 */
@Beta
@ElementTypesAreNonnullByDefault
public final class HashingOutputStream extends FilterOutputStream {
  private final Hasher hasher;

  /**
   * Creates an output stream that hashes using the given {@link HashFunction}, and forwards all

    int b = 'q';
    HashingOutputStream out = new HashingOutputStream(hashFunction, buffer);
    out.write(b);

    verify(hashFunction).newHasher();
    verify(hasher).putByte((byte) b);
    verifyNoMoreInteractions(hashFunction, hasher);
  }

  public void testWrite_putByteArray() throws Exception {
    byte[] buf = new byte[] {'y', 'a', 'm', 's'};

    int b = 'q';
    HashingOutputStream out = new HashingOutputStream(hashFunction, buffer);
    out.write(b);

    verify(hashFunction).newHasher();
    verify(hasher).putByte((byte) b);
    verifyNoMoreInteractions(hashFunction, hasher);
  }

  public void testWrite_putByteArray() throws Exception {
    byte[] buf = new byte[] {'y', 'a', 'm', 's'};