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?

I'm thinking in C is the most straightforward?

Thanks.

Solution 1

Have an array, buffer, of 5 integers. Have an index ind to the next element. When you add, do

buffer[ind] = value;
ind = (ind + 1) % 5;

Solution 2

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.

Solution 3

If the size and data type of your buffer are fixed, a simple array is all you need:

 int buffer[5];

Add to that a couple pointers:

 int* start = &buffer[0];
 int* end   = &buffer[4]+1;
 int* input = start;
 int* output = start;

Comments

[photo_tom]

From the personal experience file, you need to be careful that ind is not negative. If you change the second line to "ind = (max(0,ind) % 1) + 5;", you don't have to worry about negative values for ind.

[user3467349]

You don't need num and idx.

[Triskeldeian]

Why don't you just set ind to be uint? That would solve your problem more efficiently if only additions are involved