code: private CompletableFuture<ByteArraySegment> readPage(long offset, int length, Duration timeout) {
          return this.read.apply(offset, length, timeout);
      }
docs: Reads the contents of a single page from the external data source.
  
  @param offset  Page offset.
  @param length  Page length.
  @param timeout Timeout for the operation.
  @return A CompletableFuture with a ByteArraySegment representing the contents of the page.