Class RingBuffer

ch6-ring-buffer/ring-buffer.js:1–85

class RingBuffer {
  constructor(meta/*: Uint32Array[3]*/, buffer /*: Uint8Array */) {
    this.meta = meta;
    this.buffer = buffer;
  }

  get head() {
    return this.meta[0];
  }

  set head(n) {
    this.meta[0] = n;
  }

  get tail() {
    return this.meta[1];
  }

  set tail(n) {
    this.meta[1] = n;
  }

  get length() {
    return this.meta[2];
  }

  set length(n) {
    this.meta[2] = n;
  }

  write(data /*: Uint8Array */) { // <1>
    let bytesWritten = data.length;
    if (bytesWritten > this.buffer.length - this.length) { // <2>
      bytesWritten = this.buffer.length - this.length;
      data = data.subarray(0, bytesWritten);
    }
    if (bytesWritten === 0) {
      return bytesWritten;
    }
    if (
      (this.head >= this.tail && this.buffer.length - this.head >= bytesWritten) ||
      (this.head < this.tail && bytesWritten <= this.tail - this.head) // <3>
    ) {
      // Enough space after the head. Just write it in and increase the head.
      this.buffer.set(data, this.head);
      this.head += bytesWritten;
    } else { // <4>
      // We need to split the chunk into two.
      const endSpaceAvailable = this.buffer.length - this.head;
      const endChunk = data.subarray(0, endSpaceAvailable);
      const beginChunk = data.subarray(endSpaceAvailable);
      this.buffer.set(endChunk, this.head);
      this.buffer.set(beginChunk, 0);
      this.head = beginChunk.length;
    }
    this.length += bytesWritten;
    return bytesWritten;
  }

  read(bytes) {