/guava/guava/src/com/google/common/io/ByteSource.java
Optional<Long> optionalUnslicedSize = ByteSource.this.sizeIfKnown ( ) ;
@Override public boolean isEmpty() throws IOException { return length == 0 || super.isEmpty(); } @Override public Optional<Long> sizeIfKnown() { <extra_id_0> if (optionalUnslicedSize.isPresent()) { long unslicedSize = optionalUnslicedSize.get(); long off = Math.min(offset, unslicedSize); return Optional.of(Math.min(length, unslicedSize - off)); } return Optional.absent();