In the previous week, we encountered a diversity of errors while developing our codes for the RLE0 encoder and decoder. One of the most frequent errors we found ourselves struggling with was a mismatch between the bytes contained within the files processed by our programs and the sample files. As a way to debug those issues, some of us resorted to comparing the MD5SUMS hashes or the binaries with a hex editor of both files. In other words, we were dependent on other already existing tools to patch our bugs. However, these tools have one flaw they are not specified RLE debugging tools. If only we could find the perfect tool that meets our needs, or better yet, if only we could develop our own debugging tools for an improved RLE algorithm development experience. (I feel like I managed to channel my inner Matt there :P)

Therefore, this week, for bdb0 we are tasked to write a debug tool that will be used in future rleX projects. This debug tool will compare two binary files, one being the output of our encoder/decoder, and the other being some reference file.

BDB0 will take two arguments, two different files that will be compared to each other:

./bdb0   FILE1.txt  sample1.txt
Argv[0]  Arg[1]     Arg[2]

These files are not necessarily RLE-specific, you could use bdb0 to compare any files together.

The main focus of this program is to help us compare binaries, displayed in hexadecimal values, similar to a hex editor, only displaying the mismatched data. Hence, the output should be the line byte of discrepancy, along with the previous and following 16 bytes and the address of those bytes

*Our task is to ask questions on Discord or in class and document our findings on this wiki page collaboratively, regarding the functionality of this project.

*For anybody interested in editing the wiki page, here is the dokuwiki user guide: https://www.dokuwiki.org/wiki:syntax#basic_text_formatting -Ash

This is an example of the output of the program:

This is the structure:

The middle line, called mismatch, is the focus of the program, and it should be displayed in a different color with the use of ANSI escape codes.

The program is to display 16 bytes prior to, 16 bytes of, and 16 bytes after the first byte of difference detected in the two files. If either the 16 bytes prior or 16 bytes after the mismatch are not data from the file, in other words, you've reached the end of the file and there is no more data to display, you may display it with a NULL character (0x00, '\n').

Example: In this example you see a mismatch happening right on the very first bytes of the file. Since there is no previous data to fetch, this lack of data is then displayed as NULL.

The address portion is a line count in hexadecimal format.

The colors you use are up to you, but some coloring has to happen. So far it is required that three parts of the output are displayed in different colors, the addresses (on both sides), the data (both sides), and the mismatched bytes line.

Your program should only print the FIRST mismatch, NOT the entire document neither every mismatched line of bytes. JUST THE FIRST ONE along the previous and next bytes.

When running the program with two DIFFERENT files, the program should display the line containing the first byte that is mismatched, with the leading/post 16 bytes.

When running the program with two SAME files, the program should display nothing. The normal process of using make check to check your file against the desired result won't work in this case. The verify file is that of a different year when different specifications were desired. Running it this time around will lead you to many mismatches and headaches. You can check your output against the pictures provided above as a general guideline but other than that it is essential that if you have any questions to just ask in discord instead of guessing and hoping it is what is desired.