RingBuffer.js

export class RingBuffer {
  constructor(capacity, data = []) {
    this._capacity = capacity;
    this._buffer = new Array(this._capacity);
    this._writeIndex = 0;
    this._readIndex = 0;
    this._msgsReceived = 0;

    this._lastMeasurement = performance.now();
    this._msgsSinceLast = 0;

    if (data && data.length > 0) {
      for (let i = 0; i < data.length; i++) {
        this.write(data[i]);
      }
    }
  }

  size() {
    if (this._writeIndex + 1 === this._readIndex) {
      return this._capacity;
    } // buffer is full
    // Otherwise, buffer not full, calculate size
    return this._writeIndex >= this._readIndex
      ? this._writeIndex - this._readIndex
      : this._capacity - this._readIndex + this._writeIndex;
  }

  msgsReceived() {
    return this._msgsReceived;
  }

  msgsPerSecond() {
    const elapsedS = (performance.now() - this._lastMeasurement) / 1000;
    this._lastMeasurement = performance.now();
    const result = this._msgsSinceLast / elapsedS;
    this._msgsSinceLast = 0;

    return result;
  }

  write(value) {
    this._msgsReceived++;
    this._msgsSinceLast++;
    if (this.size() < this._capacity) {
      // not at capacity yet
      this._writeIndex = this.next(this._writeIndex);
      this._buffer[this._writeIndex] = value;
    }
  }

  read() {
    if (this.size() > 0) {
      // something available to read
      this._readIndex = this.next(this._readIndex);
      return this._buffer[this._readIndex];
    }
  }

  next(i) {
    ++i;
    if (i === this._capacity) {
      return 0;
    } else {
      return i;
    }
  }
}

export default RingBuffer;