docs: private Boolean containsKeyIntern(final ChunkCacheKey chunkCacheKey) throws IOException {
        try {
           final long length = directory.fileLength(chunkCacheKey.getFileName());
           final int bufferSize = chunkCacheKey.getBufferSize();
           final int chunkId = chunkCacheKey.getChunkId();
           return Boolean.valueOf((chunkId * bufferSize) < (length + bufferSize));
        }
        catch (NoSuchFileException nfne) {
           //Ok, we might check for file existence first.. but it's reasonable to be
           //optimistic.
           return Boolean.FALSE;
        }
     }