src/it/unimi/dsi/fastutil/io/FastBufferedInputStream.java
@Override
	public long length() throws IOException {
		if (measurableStream != null) return measurableStream.length();
		if (fileChannel != null) return fileChannel.size();
		throw new UnsupportedOperationException();
	}
@Override
	public long length() throws IOException {
		if (measurableStream != null) return measurableStream.length();
		if (fileChannel != null) return fileChannel.size();
		throw new UnsupportedOperationException();
	}
Returns the length of the underlying input stream, if it is {@linkplain MeasurableStream measurable}.

@return the length of the underlying input stream.
@throws UnsupportedOperationException if the underlying input stream is not {@linkplain MeasurableStream measurable} and
cannot provide a {@link FileChannel}.