Circular buffer
data structure
In computer science, a circular buffer, circular queue, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end. This structure lends itself easily to buffering data streams. There were early circular buffer implementations in hardware.
Overview
A circular buffer first starts out empty and has a set length. In the diagram below is a 7-element buffer:
Assume that 1 is written in the center of a circular buffer (the exact starting location is not important in a circular buffer):
Then assume that two more elements are added to the circular buffer — 2 & 3 — which get put after 1:
If two elements are removed, the two oldest values inside of the circular buffer would be removed. Circular buffers use FIFO (first in, first out) logic. In the example, 1 & 2 were the first to enter the circular buffer, they are the first to be removed, leaving 3 inside of the buffer. When elements get removed, only the read-pointer moves to the next element. Removed elements are still in the buffer, waiting to get overwritten by new elements.
If the buffer has 7 elements, then it is completely full:
A property of the circular buffer is that when it is full and a subsequent write is performed, then it starts overwriting the oldest data.
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This entry incorporates text from “Circular buffer” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.