A Linear Time, Constant Space Differencing Algorithm

An efficient differencing algorithm can be used to compress version of files for both transmission over low bandwidth channels and compact storage. This can greatly reduce network traffic and execution time for distributed applications which include software distribution, source code control, file system replication, and data backup and restore. An algorithm for such applications needs to be both general and efficient; able to compress binary inputs in linear time. We present such an algorithm for differencing files at the granularity of a byte. The algorithm uses constant memory and handles arbitrarily large input files. While the algorithm makes minor sacrifices in compression to attain linear runtime performance, it outperforms the byte-wise differencing algorithms that we have encountered in the literature on all inputs.