Tiny Circular Buffer - back to linear

A project log for limited-code hacks/ideas

When you're running out of code-space... sometimes yah's gots to hack. Here are some ideas.

eric-hertzEric Hertz 12/30/2016 at 04:110 Comments

I need to add elements to the end of a buffer, and remove elements from the beginning... It can have from 0 to 4 elements loaded at a time.

The de-facto answer might be a circular-buffer.

But this buffer is only 4 elements long...

It would seem that implementing this as a simple array would be more efficient, in my case. Yes, it means that when I remove an element from the beginning, I have to shift the remaining data to the beginning...

And, the de-facto answer might be a for() loop...

But, again, there's only four elements. So, unroll that loop, as well.

(Note that the optimizer can look at short fixed-count for() loops, and automatically "unroll" them... I'm pretty much certain that this case will be smaller unrolled, and I'm not entirely convinced my optimizer-settings will do-so, so I'll type it manually.)


Interestingly, doing this as a simple array, rather than a circular-buffer, also dramatically decreased the amount of code in nearly every other function, e.g. buffer_add(), buffer_countElements(), buffer_isFull(), buffer_clear()... In fact, many of these functions are now merely comparisons/assignments to a variable such as buffer_itemCount. So, now, whereas I had multi-line functions that *could*'ve been inlined to reduce code-space in a few cases, now it's *definitely* more code-space (and execution-time!) efficient to inline these functions in every case.