memcpy rather than loop?

[redorkulated]

Hey,

Great bit of code, should save me from using openssl (hopefully)! Just curious, on this section what made you use a loop rather than just memcpy(output,input,KEYLEN) ?:

static void BlockCopy(uint8_t* output, uint8_t* input) { uint8_t i; for (i=0;i<KEYLEN;++i) { output[i] = input[i]; } }

Of course memcpy itself is a call and then another loop but it might on some computers/compilers it might be more optimised then byte by byte copying

[kokke]

Hi Michael,

Thanks for the kinds words :) I appreciate your interest in my project.

Your guess is correct, it is to save a function call and avoid the dependency on memcpy.
The reason is also that it produces the smallest code output using the compilers I've benchmarked. It is a valid candidate for optimization if you are already linking memcpy into the C runtime, sure :)

[redorkulated]

Very interesting :D , I do love it how you can start to refine C down so much to save on ASM instructions! I have never had to work in an embedded environment but I still love to worry about each byte and instruction being pointlessly wasted.

[kokke]

The project started out because I needed the algorithm but didn't have enough space for what I could download on the web :)

There are smaller implementations, which I haven't had the time to review.
Links in this issue:
#17