Landon Curt Noll
4ee4c731f7
While not strictly necessary, replacing the two ASCII tab characters in the markdown copyright comment makes it easier to detect problematic TAB indentation within markdown files. After this commit, only 90 markdown files have leading ASCII TAB characters. And again, while not strictly necessary, we can consider running expand on those 90 markdown files to see what effect that might have on the HTML files they produce. Replace leading ASCII TAB characters with multiples of 8 ASCII SPACE characters (the default action of the `expand(1)` tool) might have an negative effect on some HTML formatting where **hack-a-round** formatting was attempted to fix broken indentation caused by problematic ASCII TAB characters. Think of this as a baseline for evaluating leading TAB characters within markdown files. TODO: Consider either using `expand(1)` to replace leading ASCII TAB characters with multiples of 8 ASCII SPACE characters AND/OR modifying the appropriate `bin` tool to convert leading ASCII TAB characters into multiples of 8 ASCII SPACE characters.
129 lines
3.5 KiB
Markdown
129 lines
3.5 KiB
Markdown
## To build:
|
|
|
|
``` <!---sh-->
|
|
make
|
|
```
|
|
|
|
There are alternate versions of this entry. See [Alternate
|
|
code](#alternate-code) below for more details.
|
|
|
|
|
|
## To use:
|
|
|
|
``` <!---sh-->
|
|
./prog
|
|
# input some text
|
|
|
|
echo text | ./prog
|
|
|
|
./prog < file
|
|
```
|
|
|
|
|
|
## Try:
|
|
|
|
``` <!---sh-->
|
|
./try.sh
|
|
```
|
|
|
|
|
|
## Alternate code:
|
|
|
|
There are a number of alternate versions for this program, some in C and some in
|
|
assembly.
|
|
|
|
The file [prog.alt.c](%%REPO_URL%%/2020/kurdyukov1/prog.alt.c) is smaller and does not contain any
|
|
headers or any workaround for WIN32 based platforms.
|
|
|
|
The file [prog.extra.c](%%REPO_URL%%/2020/kurdyukov1/prog.extra.c) has a number of layouts including some for
|
|
different social media profile covers as well as different shapes.
|
|
|
|
The files [prog.x86_64.asm](%%REPO_URL%%/2020/kurdyukov1/prog.x86_64.asm) and [prog.x86.asm](%%REPO_URL%%/2020/kurdyukov1/prog.x86.asm)
|
|
are the program in assembly for x86_64 linux and x86 linux respectively.
|
|
|
|
|
|
### Alternate build:
|
|
|
|
To build [prog.alt.c](%%REPO_URL%%/2020/kurdyukov1/prog.alt.c):
|
|
|
|
``` <!---sh-->
|
|
make alt
|
|
```
|
|
|
|
|
|
### Alternate use:
|
|
|
|
Use `prog.alt` as you would `prog` above.
|
|
|
|
|
|
## Judges' remarks:
|
|
|
|
This hash of a C code makes a hash out of input.
|
|
Do you understand how?
|
|
You should get a-round-to-it figuring it out!
|
|
|
|
|
|
## Author's remarks:
|
|
|
|
### MD5 with integers
|
|
|
|
Just a tiny MD5 checksum utility. Prints hash string of data from `stdin`.
|
|
Works the same as `openssl md5 | cut -d' ' -f2` command.
|
|
|
|
### My objectives
|
|
|
|
1. Reduce code size as much as possible.
|
|
2. Avoid warnings from gcc/clang `-Wall -Wextra -pedantic`.
|
|
3. Portable (regardless of register size and endianness).
|
|
4. Fit code in a round shape.
|
|
5. Mo macro defines.
|
|
6. No floating-point arithmetics.
|
|
|
|
|
|
### Notes
|
|
|
|
The main difficulty of making MD5 code smaller is a 64x4 bytes long table with
|
|
constants which will take more than 512 bytes in hex encoding. This table is a
|
|
results of a sine function, so can be generated dynamically, but merging
|
|
floating-point arithmetics with precise integer calculations is not a great
|
|
idea, because it can cause portability issues.
|
|
|
|
Attempts to satisfy `clang -Weverything` will ruin comma magic, that is so great
|
|
for obfuscation, so I don't want to care about that.
|
|
|
|
Probably, should work correctly on any machines, but I have nothing exotic (like
|
|
BE or not 32/64) to try it.
|
|
|
|
Added a macro hack to make `stdin` work in binary mode under Windows (tested
|
|
under mingw64), otherwise the hashes can be incorrect.
|
|
|
|
|
|
### Bonus
|
|
|
|
- [prog.extra.c](%%REPO_URL%%/2020/kurdyukov1/prog.extra.c) is the same with the sine function (so smaller),
|
|
and in different shapes.
|
|
|
|
- [prog.x86_64.asm](%%REPO_URL%%/2020/kurdyukov1/prog.x86_64.asm) contains the same program, but written in
|
|
assembly for x86_64 Linux, for the sake of smaller executable size which is 500
|
|
bytes long (where 120 is for the ELF headers) after compilation. Algorithm
|
|
details is slightly different (like constants packing), just to make smaller
|
|
binary code. It's interesting to compare density of binary code and obfuscated
|
|
C.
|
|
|
|
- [prog.x86.asm](%%REPO_URL%%/2020/kurdyukov1/prog.x86.asm) is for x86, although the headers are smaller, but
|
|
the binary code is larger due to fewer registers and lack of 64-bit multiply.
|
|
|
|
<!--
|
|
|
|
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
|
|
|
You are free to share and adapt this file under the terms of this license:
|
|
|
|
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
|
|
|
For more information, see:
|
|
|
|
https://creativecommons.org/licenses/by-sa/4.0/
|
|
|
|
-->
|