Just code that damn ring buffer yourself, it'll do good for you.
For an extremely naive solution though that will work in 10 seconds (that you should not consider a proper implementation and never quote on me telling you to write it like that), on every iteration just shift out the first element from the array and when you're done with it just push it back to the end of the array. (like that:
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Let me repeat, it's a bad solution in the general case because it has has terrible performance implications AND it's extremely vulnerable to concurrency issues should it be implemented on a platform that supports concurrent executions.