Ring Buffers

Jay McCarthy <jay at plt-scheme dot org>

(require (planet jaymccarthy/ring-buffer:1:0))

This package defines an imperative, overwritting ring buffer that holds a finite number of elements and may be used as a sequence.

(ring-buffer? v) → boolean?

v : any/c

Determines if v is a ring buffer.

(empty-ring-buffer max) → ring-buffer?

max : exact-nonnegative-integer?

Constructs an empty ring buffer that may hold max elements.

(ring-buffer-length rb) → exact-nonnegative-integer?

rb : ring-buffer?

Returns the length of rb.

(ring-buffer-push! rb v) → void

rb : ring-buffer?

v : (and/c any/c (not/c false/c))

Pushes v on to the end of rb, potentially pushing the first element of rb off.

Examples:

(define rb (empty-ring-buffer 3))

> (ring-buffer-push! rb 1)

> (ring-buffer-push! rb 2)

> (ring-buffer-push! rb 3)

> (for/list ([v rb]) v)

(1 2 3)

> (ring-buffer-push! rb 4)

> (for/list ([v rb]) v)

(2 3 4)

(ring-buffer-ref rb i) → (or/c any/c false/c)

rb : ring-buffer?

i : exact-nonnegative-integer?

Returns the value in the ith position of rb.

This interacts with ring-buffer-push!.

Examples:

(define rb (empty-ring-buffer 3))

> (ring-buffer-push! rb 1)

> (ring-buffer-push! rb 2)

> (ring-buffer-push! rb 3)

> (for/list ([v rb]) v)

(1 2 3)

> (ring-buffer-ref rb 1)

2

> (ring-buffer-push! rb 4)

> (ring-buffer-ref rb 1)

3

(ring-buffer-set! rb i v) → void

rb : ring-buffer?

i : exact-nonnegative-integer?

v : (and/c any/c (not/c false/c))

Sets the value in the ith position of rb to v

This interacts with ring-buffer-push!.