Improvements for people who want to port the code to another language

[mcraiha]

Hi,

I just completed my first port of the QOA to C#, and I noticed couple of things that could be improved in original code, to make the porting process a bit easier.

((v > 0) - (v < 0)) - ((n > 0) - (n < 0))
Many languages do not return 1 or 0 values for comparisons so this part requires some extra unfolding

qoa_uint64_t best_rank = -1;
-1 is not a valid value for unsigned integers in many languages. Maybe ULONG_MAX would be more suitable?

int slice_len = qoa_clamp(QOA_SLICE_LEN, 0, frame_len - sample_index);
int slice_start = sample_index * channels + c;
int slice_end = (sample_index + slice_len) * channels + c;

sample_index, channels, c and slice_len are always 0 or larger (and e.g. sample_index is unsigned), so using int type does not work without casting. Maybe size_t might be more suitable for indexing purposes?

qoa->lms[c].history[i] = ((signed short)(history >> 48));
and
qoa->lms[c].weights[i] = ((signed short)(weights >> 48));
should short be used instead of signed short?