We have described the design, implementation, and performance of in-place rsync for synchronizing files among mobile and wireless devices. Ip-rsync is a modification to the open-source rsync utility so that files may be updated in-place: in the memory or storage that the current version occupies. The algorithms of ip-rsync use a graphical representation of the operations in an rsync encoding to detect when in-place updates would corrupt data, and then topologically sorts these operations to avoid such conflicts. When compared with rsync, ip-rsync loses 0.5% compression from encoding overheads and breaking cyclic dependencies. Ip-rsync increases transfer time in bandwidth-constrained environments, but can increase performance in I/O constrained environments by avoiding the creation of a temporary file.
Although in-place reconstruction can degrade both compression and transfer time, it makes file synchronization available in space-constrained environments where rsync alone does not function. The benefits of file synchronization can be brought to mobile and wireless devices in exchange for minor performance losses.