https://github.com/barrettotte/qr-asm
Generate a QR code from scratch with only ARM assembly.
https://github.com/barrettotte/qr-asm
arm arm-assembly arm-assembly-language assembly pbm-image qrcode qrcode-generator reed-solomon
Last synced: 13 days ago
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Generate a QR code from scratch with only ARM assembly.
- Host: GitHub
- URL: https://github.com/barrettotte/qr-asm
- Owner: barrettotte
- License: mit
- Created: 2021-06-01T13:55:08.000Z (almost 4 years ago)
- Default Branch: master
- Last Pushed: 2021-09-06T21:17:34.000Z (over 3 years ago)
- Last Synced: 2025-03-25T13:51:10.574Z (about 1 month ago)
- Topics: arm, arm-assembly, arm-assembly-language, assembly, pbm-image, qrcode, qrcode-generator, reed-solomon
- Language: Assembly
- Homepage:
- Size: 480 KB
- Stars: 107
- Watchers: 4
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# qr-asm
Generate a QR code from scratch with only ARM assembly.
A byte mode QR code of https://github.com/barrettotte using Q error correction level.
See qrcode.pbm for the raw image file.
## Why?
At first, I learned how QR codes worked with an ugly python implementation; See [docs/python](docs/python).
Midway through the python implementation, I started to learn ARM assembly. But, I had no idea what to build
to practice my knowledge.
So, this project turned into a giant coding challenge just to see if I could do it.
In a world where C exists, you should obviously never use assembly for this type of project/application.
## Usage
`Usage: qrcode msg err_lvl`
valid error levels: `L=1, M=0, Q=3, H=2`
My primary test - `./bin/qrcode "https://github.com/barrettotte" 3`
Quick build and test - `make && make test`
## Limitations
I constrained the QR code generation a lot. I just wanted to encode a url, not build a whole library.
- Byte mode encoding only
- QR version 4 and below (up to 80 characters with v4-L)
- Mask evaluation not implemented, hardcoded to mask 0 (I think masks only effect scan efficiency)
- Instead of implementing an entire image file format, I used the [PBM](https://en.wikipedia.org/wiki/Netpbm) file format to create my QR code image.
Additionally, I'm still a novice with assembly so there is probably a ton of unoptimized code.
I also didn't use all the features of the ARM assembler/architecture.
I wanted to write this so a year from now a dummy like me could understand what I wrote.
### Debugging with GDB
I'm still new to GDB, but this worked for me.
- `make && make qemu`
- `make debug`
For sanity checking this ugly thing, see my notes in [docs/3Q-test.md](docs/3Q-test.md)
## References
- [ARM A32 Calling Convention](https://en.wikipedia.org/wiki/Calling_convention#ARM_(A32))
- [ARM 32-bit EABI Syscall Reference](https://chromium.googlesource.com/chromiumos/docs/+/master/constants/syscalls.md#arm-32_bit_EABI)
- [GNU ARM Assembler Quick Reference](https://www.ic.unicamp.br/~celio/mc404-2014/docs/gnu-arm-directives.pdf)
- [QR Code Design Wiki](https://en.wikipedia.org/wiki/QR_code#Design)
- [QR Code Tutorial](https://www.thonky.com/qr-code-tutorial/)
- [Reed Solomon Codes for Coders](https://en.wikiversity.org/wiki/Reed%E2%80%93Solomon_codes_for_coders)
- [GDB Command Reference](https://visualgdb.com/gdbreference/commands/x)
- [PBM File Description](https://oceancolor.gsfc.nasa.gov/staff/norman/seawifs_image_cookbook/faux_shuttle/pbm.html)
- [Netpbm Wiki](https://en.wikipedia.org/wiki/Netpbm)