bsdiff

An experimental tool to diff bitstream files

I'm trying to reverse engineer some proprietary binary files, and I noticed that these files are bit streams (as opposed to byte stream).

My approach is to compare two files that have minimal diferrence and see how the bitstream behave, I need to be able to detect bit flips as well as bit insertion/deletion between two files.

This is a very beta version of such a tool, it attempts to mimic the unix diff tool, but display bits instead of text.

For now, the algorithm is very stupid and simple, it doesn't yet understand the concept of context as used in GNU diff and patch.

I might improve this tool to fit my needs.

Example output

In the example below, you can see that at position 0, the first file contains 1100 where as the second file contains 0010.

Then the files are identical up to the 144975'th bit. At this bit position, the first file contains 110 whereas the second one contains 01100, that is the second file as 2 more bits that the first one.

The two files have then roughly 10k identical bits, after which there a new difference 110 vs 011010110, ...

As you might have noticed, this tool is able to track bit assertion and removal.

$ bsdiff Si8605AC-B-IS1.bxl Si8606AC-B-IS1.bxl
--- Si8605AC-B-IS1.bxl
+++ Si8606AC-B-IS1.bxl
@@ [4,0] -4,-4 +4,4 @@
-1100
+0010
 ^^^
@@ [3,2] -144975,-3 +144975,5 @@
-  110
+01100
 ^^ ^
@@ [3,6] -152419,-3 +152421,9 @@
-      110
+011010110
 ^^^^^^
@@ [2,0] -154292,-2 +154300,2 @@
-11
+01
 ^
...

Sample files

https://www.silabs.com/products/power/isolators/Pages/Si86xx-Digital-Isolators.aspx