CircularBuffer

Circularbuffer, also known as a circular buffer or ring buffer, is a fixed-size data structure that uses a single contiguous block of memory to store elements in a circular fashion. It maintains two indices: a write position (head) and a read position (tail). Data is written at the head and read from the tail, with both pointers wrapping around to the start when they reach the end.

Enqueue and dequeue operations advance the corresponding pointer by one position modulo the buffer length. A separate count of the number of elements is often kept to distinguish a full buffer from an empty one, since head equals tail can indicate either state. Some implementations use a capacity minus one trick, or rely on head and tail alone with a convention to interpret full versus empty.

Performance characteristics: Access and update are constant time, and data locality is good due to contiguous storage. The buffer has a fixed capacity, so attempts to add data when it is full require a policy: overwrite the oldest data, block until space is available, or signal an overflow to the caller.

Variants and usage: Circular buffers are common in embedded and systems programming and serve as producer–consumer queues, audio and video buffering, and I/O pipelines. Many languages provide libraries or built-in support; for concurrent access, synchronization or lock-free designs are used to ensure correctness.

Implementation notes: Many implementations keep a length counter or use head and tail differences modulo capacity. A common trick is to reserve one slot to distinguish full from empty. Wrap-around is achieved with modular arithmetic or, when the capacity is a power of two, with bitwise masking for efficiency.

Applications: Streaming data, network I/O, logging, real-time data acquisition, and media processing. Circularbuffers provide predictable memory use and fast, constant-time operations, with careful handling required for full buffers and concurrency.