*
   * @param sources the sources to concatenate
   * @return a {@code ByteSource} containing the concatenated data
   * @since 15.0
   */
  public static ByteSource concat(Iterable<? extends ByteSource> sources) {
    return new ConcatenatedByteSource(sources);
  }

  /**
   * Concatenates multiple {@link ByteSource} instances into a single source. Streams returned from

  public void testConcat() throws IOException {
    ByteSource b1 = ByteSource.wrap(new byte[] {0, 1, 2, 3});
    ByteSource b2 = ByteSource.wrap(new byte[0]);
    ByteSource b3 = ByteSource.wrap(new byte[] {4, 5});

    byte[] expected = {0, 1, 2, 3, 4, 5};

    assertArrayEquals(expected, ByteSource.concat(ImmutableList.of(b1, b2, b3)).read());
    assertArrayEquals(expected, ByteSource.concat(b1, b2, b3).read());

  public void testConcat() throws IOException {
    ByteSource b1 = ByteSource.wrap(new byte[] {0, 1, 2, 3});
    ByteSource b2 = ByteSource.wrap(new byte[0]);
    ByteSource b3 = ByteSource.wrap(new byte[] {4, 5});

    byte[] expected = {0, 1, 2, 3, 4, 5};

    assertArrayEquals(expected, ByteSource.concat(ImmutableList.of(b1, b2, b3)).read());
    assertArrayEquals(expected, ByteSource.concat(b1, b2, b3).read());

  }

  // Test that you can not expand the readable data in a previously sliced ByteSource.
  public void testSlice_constrainedRange() throws IOException {
    long size = source.read().length;
    if (size >= 2) {
      ByteSource sliced = source.slice(1, size - 2);
      assertEquals(size - 2, sliced.read().length);
      ByteSource resliced = sliced.slice(0, size - 1);
      assertTrue(sliced.contentEquals(resliced));
    }

        } else {
          return TO_BYTE_ARRAY_NEW_STRING.read(byteSource, cs);
        }
      }
    };

    abstract String read(ByteSource byteSource, Charset cs) throws IOException;
  }

  @Param({"UTF-8"})
  String charsetName;

  @Param ReadStrategy strategy;

  @Param({"10", "1024", "1048576"})
  int size;

  Charset charset;
  ByteSource data;

  @BeforeExperiment
  public void setUp() {

        } else {
          return TO_BYTE_ARRAY_NEW_STRING.read(byteSource, cs);
        }
      }
    };

    abstract String read(ByteSource byteSource, Charset cs) throws IOException;
  }

  @Param({"UTF-8"})
  String charsetName;

  @Param ReadStrategy strategy;

  @Param({"10", "1024", "1048576"})
  int size;

  Charset charset;
  ByteSource data;

  @BeforeExperiment
  public void setUp() {

    File file = fileAndSource.file;
    WeakReference<ByteSource> sourceRef = fileAndSource.sourceRef;
    fileAndSource = null;
    awaitClear(sourceRef);
    awaitDone(() -> !file.exists());
  }

  private static final class FileAndWeakByteSource {
    final File file;
    final WeakReference<ByteSource> sourceRef;

    FileAndWeakByteSource(File file, WeakReference<ByteSource> sourceRef) {
      this.file = file;

    this.state = new State(fileThreshold, resetWhenGarbageCollected);
    this.byteSource = new FbosByteSource(state);

    if (resetWhenGarbageCollected) {
      FinalizableReference.register(byteSource);
    }
  }

  private static final class FinalizableReference extends FinalizablePhantomReference<ByteSource> {
    static final FinalizableReferenceQueue referenceQueue = new FinalizableReferenceQueue();

  }

  // Test that you can not expand the readable data in a previously sliced ByteSource.
  public void testSlice_constrainedRange() throws IOException {
    long size = source.read().length;
    if (size >= 2) {
      ByteSource sliced = source.slice(1, size - 2);
      assertEquals(size - 2, sliced.read().length);
      ByteSource resliced = sliced.slice(0, size - 1);
      assertTrue(sliced.contentEquals(resliced));
    }

@GwtIncompatible
final class MultiInputStream extends InputStream {

  private final Iterator<? extends ByteSource> it;
  private @Nullable InputStream in;

  /**
   * Creates a new instance.
   *
   * @param it an iterator of I/O suppliers that will provide each substream
   */
  public MultiInputStream(Iterator<? extends ByteSource> it) throws IOException {
    this.it = checkNotNull(it);
    advance();
  }

  @Override