Class PushQueue

src/push.ts:73–542

* Internal queue with chunk-based backpressure. * * This implements the core buffering logic shared between writer and readable. * - Chunk-oriented backpressure: counts write/writev calls, not bytes * - Configurable highWaterMark (default: 4) * - Four backpressure policies: strict, block, drop-

 * - drop-newest: discards new write (pendingWrites unused)
 */
class PushQueue {
  /** Buffered chunks (each slot is from one write/writev call) */
  private slots = new RingBuffer<Uint8Array[]>();

  /** Pending writes waiting for buffer space (strict policy only) */
  private pendingWrites = new RingBuffer<PendingWrite>();

  /** Pending reads waiting for data */
  private pendingReads = new RingBuffer<PendingRead>();

  /** Pending drains waiting for backpressure to clear */
  private pendingDrains: PendingDrain[] = [];

  /** Writer state */
  private writerState: WriterState = 'open';

  /** Consumer state */
  private consumerState: ConsumerState = 'active';

  /** Error that closed the stream */
  private error: any = null;

  /** Total bytes written */
  private bytesWritten = 0;

  /** Configuration */
  private readonly highWaterMark: number;
  private readonly backpressure: BackpressurePolicy;

  /** Abort signal */
  private signal?: AbortSignal;
  private abortHandler?: () => void;

  constructor(options: PushStreamOptions = {}) {
    this.highWaterMark = Math.max(1, options.highWaterMark ?? 4);
    this.backpressure = options.backpressure ?? 'strict';
    this.signal = options.signal;

    if (this.signal) {
      if (this.signal.aborted) {
        this.fail(this.signal.reason instanceof Error
          ? this.signal.reason
          : new DOMException('Aborted', 'AbortError'));
      } else {
        this.abortHandler = () => {
          this.fail(this.signal!.reason instanceof Error
            ? this.signal!.reason
            : new DOMException('Aborted', 'AbortError'));
        };
        this.signal.addEventListener('abort', this.abortHandler, { once: true });
      }
    }
  }

  // ===========================================================================
  // Writer Methods
  // ===========================================================================