Algorithm of Encoding FT8?

[fahadh4ilyas]

I've been reading the paper but it seems the paper didn't include algorithm or pseudocode of encoding FT8. I'm trying to read your code but because I'm still novice in C, I only understand the general concept but still struggle with the detail like:

1. How packed turned into tones. I understand the step is CRC -> LDPC -> Costas. I know how CRC works, but LDPC and Costas still puzzling me.
2. How to synthesize waveform data (signal). I thought we only needs to do FFT to tones. But, I don't understand at all how the code works because I don't see the use of FFT anywhere.

So, is there any algorithm or pseudocode that I can learn from to encode FT8? I really appreciate if you have it. Thanks for considering my request.