"difference patching" help

[ctlajoie]

"difference patching" is my word for the method used by patch makers that take only the differences in two files, and apply them to a patch file. RTPatch is an example of a program that does this.

I've been trying to create one myself, but I'm stuck on the logic. The only way I can think of to do it is to compare the bits in both of the files, and if oldfile[x] != newfile[x] then save the offset and value of newfile[x] to the patch file.

I don't think that's the way it should be done, because nearly all the bits will be different, and you'll end up with a larger patch file than it would be with any other patch program.

Maybe I just need a fresh perspective on it, but I can't think of a more efficient way of doing it. Can anyone help?

[BountyX]

have you considered using recursion ;) think about it and post back if you need help setting it up

[infamous]

try comparing line by line, not bit by bit.

[BountyX]

try comparing line by line, not bit by bit.

comparing line by line might be errorneous, but if not its worth a shot. If your trying to patch a file by getting the asic contents of one exe and comparing it with the asci contents of another, that won't work.