Is there a way to diff files from C++?

Question

I'm looking for a C or C++ diff library. I know I can use the Unix diff tool in combination with system or exec, but I really want a library. It would be handy if the library could perform patches as well, like the Unix patch tool.

Answer 1

Subversion includes a library libsvn_diff.

Answer 2

It seems like the Google Diff, Match and Patch libraries are what you need.

Answer 3

This is an implementation of a "solution to SES/LCS with the Hirschberg linear space refinement as described in the following publication":

E. Myers, ``An O(ND) Difference Algorithm and Its Variations,'' Algorithmica 1, 2 (1986), 251-266. http://www.cs.arizona.edu/people/gene/PAPERS/diff.ps

Found it on the Wikipedia page on diff.

That's only for finding a diff though, not applying it as a patch. I think that application of a patch is actually a harder problem; due to the risk of conflicts. It would need some form of user-controlling feedback mechanism, to resolve conflicts.

Answer 4

Also pretty much unfindable in Google, it turns out that Gnulib has a diff module. This one seems sufficient for what I wanted a diff library for. It doesn't seem to have a patch module, though.

Answer 5

I think I've found a good solution, finally:

The DTL - Diff Template Library --- Tutorial

It supports patch. I had to type "diff.cpp" into Google to find it. Hopefully it works!

Answer 6

There is one that is part of Mercurial. It exists as some C code that's designed as a Python extension, but it could probably be extracted pretty easily. I believe it can also do binary diffs.

The relevant .c files are mercurial/bdiff.c, mercurial/mpatch.c and possibly mercurial/diffhelpers.c.