diffprep

v2021.97

Abstract

This project is about a preprocessor/postprocessor for "diff" and "patch", allowing to create word-, character-, byte- or bit-based diffs and patches.

It can also be "mis-used" as a hex-dump or bit-dump utility, supporting the conversion of manually edited dump files back to the original binary data (similar to "xxd -r").

The utility has no external library dependencies and only uses the standard C runtime library.

It is written in portable ANSI-C 89 as a single source file, and should therefore be easy to build and install.

Keywords

word-diff, character-diff, bit-diff, hexdump, reverse hexdump, bit-dump, reverse bit-dump, word-based merge, character-based merge, bit-based merge, word-wrapped merge, binary diff, binary patch, binary merge.

Examples

Word-diff files 1.txt and 2.txt with bash as shell:

$ diff -u <(diffprep 1.txt) <(diffprep 2.txt)

The same with a normal POSIX shell:

$ diffprep 1.txt > 1.words
$ diffprep 2.txt > 2.words
$ diff -u 1.words 2.words

Create a hex-dump similar to "hexdump -C 1.txt":

$ diffprep -axn16 1.txt

Create an editable hexdump of file data.bin with 20 bytes per line:

$ diffprep -xn20 data.bin > data.hex

Re-create binary file data.bin from data.hex after manually editing that file:

$ diffprep -X data.hex > data.bin

Create a patch out.wdiffs from the word-based differences of 1.txt and 2.txt which treats all whitespace equal (newlines and normal spaces will be considered equal). Then apply that patch to some file 1-modified.txt, again treating newlines and spaces as interchangable:

$ diffprep 1.txt > 1.words
$ diffprep 2.txt > 2.words
$ diff -bu 1.words 2.words > out.wdiffs

$ diffprep 1-modified.txt > 1-modified.words
$ patch -l 1-modified.words out.wdiffs
$ diffprep -W 1-modified.words > 1-modified.txt

Compare two 24-bit RGB bitmap image files base.png and base_w_logo.png and show the different RGB pixels (requires imagemagick to be installed):

$ convert base.png base.ppm
$ convert base_w_logo.png base_w_logo.ppm
$ ppm2rgb() { local x; for x in `seq 3`; do read x; done; cat; }
$ ppm2rgb < base.ppm > base.rgb
$ ppm2rgb < base_w_logo.ppm > base_w_logo.rgb
$ diffprep -xn3 base.rgb > base.hex3
$ diffprep -xn3 base_w_logo.rgb > base_w_logo.hex3
$ diff -u base.hex3 base_w_logo.hex3

Display the different bits of two bitstream files 1.bin and 2.bin:

$ diffprep -b 1.bin > 1.bits
$ diffprep -b 2.bin > 2.bits
$ diff -u 1.bits 2.bits

How to build

Under UNIX, Linux, Cygwin or MinGW it is simple: Just run

$ make

to compile and build the program. If you want to build with specific compiler flags, you can invoke 'make' like this instead:

$ make CFLAGS="-D NDEBUG -O2 -s"

If you don't have a POSIX-compliant "make" utility, but some C/C++ IDE is available instead, just create a new C project in your IDE and import diffprep.c as the only source file. Then build the project.

If you have neither "make" nor an IDE, you might still have a C compiler installed. Try this:

$ cc -o diffprep -D NDEBUG -s -O2 diffprep.c

In all cases, after successful compilation, run

$ ./diffprep -h

for displaying help, copyright and usage information.

You might also want to to install the built executable, so that it can be invoked from anywhere:

$ sudo cp diffprep /usr/local/bin/

License Information

Copyright (c) 2016-2021 Guenther Brunthaler. All rights reserved.

This program is free software. Distribution is permitted under the terms of the GPLv3.