kevidryon2/japp

A program for patching executables or other files, useful for example when you want to distribute a mod without distributing the entire game.

JAPP

A program for patching executables or other files.

Use cases

For example, JAPP is useful when you want to distribute a mod without distributing the entire game, especially if that game is paid.

How to use

Patching

To patch the original game/program/anything else, first you have to put all the files of the software inside a ZIP file.

Then, you apply the patch to the ZIP file and the mask, using the JAPP CLI japp-patch.

Creating a patch and mask

All you need is a ZIP archive of the original program and a ZIP archive of the modified version. Then, you can create a patch (.jp) and a mask (.jm) using the JAPP CLI japp-unpatch

How it works

Patching

japp-patch sets every byte in the file to be patched to the corresponding byte in the patch file, but only if the corresponding bit in the mask file is set.

Creating a patch and mask

japp-unpatch compares the differences between the original file and the modified file, and stores those differences in the patch and mask files.