This application prepares and generates diff files (deltas and signatures) to allow user update files without need to send the whole data. It's especially useful when it comes to update large files. It's much more efficient to send Kilobytes or even Megabytes instead of Gigabytes, isn't it?
Usage: ./jdiff target {required args} [options]
target options:
-s, --signature <base_file_path> {-o } [-x | -f] Create signature file
-d, --delta <signature_path> {-i | -o } [-x | -f] Create delta file
-p, --patch <base_file_path> {-i | -o } [-x | -f] Patch file
-h, --help Print help
arg options:
-i, --input <file_path> Additional input file
-o, --output <output_path> Output file
more options:
-x, --sha Enable sha hashing
-f, --force Force output overwrite
-b, --block-size Block size to hash (not recommended!)
Basic block size is set to 4096, but it will be recalulated for files smaller than 8192 bytes. To provide at least two signature chunks for file.
Rolling hash checksum is 32 bit variable created by concatenation of two 16 bit sums, so it's reasonable to keep both values in uint16 range (0 - 65535). But there are lots of suggestions in the web to use the largest prime number in this range to reduce repetitions or cycles.
- Program creates or overwrites file (signature, delta or recreated one) in the filesystem.
- Program returns overwrite prompt when output file already exists (without force option).
- Program returns "Error: " message if:
- file provided doesn't exist.
- file is empty.
- delta sha and base file sha don't match.
https://www.andrew.cmu.edu/course/15-749/READINGS/required/cas/tridgell96.pdf
https://iq.opengenus.org/rolling-hash/
https://en.wikipedia.org/wiki/Rolling_hash
https://github.com/WayneD/rsync - read, for research purposes
https://github.com/catchorg/Catch2 - one header lib used for testing
https://github.com/stbrumme/xxhash - fast 64bit hashing algorithm
https://github.com/jarro2783/cxxopts - input parser and help printer
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