Method size

guava/src/com/google/common/io/ByteSource.java:204–229

Returns the size of this source in bytes, even if doing so requires opening and traversing an entire stream. To avoid a potentially expensive operation, see {@link #sizeIfKnown}. <p>The default implementation calls {@link #sizeIfKnown} and returns the value if present. If absent, it will fall back

()

   * @throws IOException if an I/O error occurs while reading the size of this source
   */
  public long size() throws IOException {
    Optional<Long> sizeIfKnown = sizeIfKnown();
    if (sizeIfKnown.isPresent()) {
      return sizeIfKnown.get();
    }

    Closer closer = Closer.create();
    try {
      InputStream in = closer.register(openStream());
      return countBySkipping(in);
    } catch (IOException e) {
      // skip may not be supported... at any rate, try reading
    } finally {
      closer.close();
    }

    closer = Closer.create();
    try {
      InputStream in = closer.register(openStream());
      return ByteStreams.exhaust(in);
    } catch (Throwable e) {
      throw closer.rethrow(e);
    } finally {
      closer.close();
    }
  }

  /** Counts the bytes in the given input stream using skip if possible. */
  private static long countBySkipping(InputStream in) throws IOException {