FILE TRANSFER METHOD AND APPARATUS USING HASH NUMBERS

摘要

The present invention facilitates and speeds the transmission of a copy of a new file (13) to a receiving computer (2) where the receiving computer (2) has an old file (23). The sending computer (1) does not know the status or content of the old file (23). As a preliminary step, the receiving computer divides the old file into segments, and calculates a hash number for each segment. The receiving computer (2) then transmits these hash numbers to the sending computer (1). The sending computer (1) examines each segment in the new file (13) to determine which, if any, segments in the new file (13) have hash numbers that match the hash numbers received from the receiving computer (2). The sending computer (1) sends to the receiving computer (2) those bytes from the new file (13) that are not part of any matching segment and an indication where matching segments fit into the new file (13). Finally, the receiving computer (2) constructs a copy of the new file (13C) from the bytes received and from the matching segments in the old file (23).