How do I code a simple integer circular buffer in C/C++?

Question

I see a lot of templates and complicated data structures for implementing a circular buffer.

How do I code a simple integer circular buffer for 5 numbers?

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Answer 1

Take an array, arr, an index idx, and a counter, num.

To insert foo, say arr[idx++] = foo; idx %= buffer_len; num++;.

To read out an item into foo, say foo = arr[(idx-num)%buffer_len]; num--;.

Add boundary checks.