Function makeReadableWebSocketStream

edge/LoadBalance.js:250–305

* * @param {import("@cloudflare/workers-types").WebSocket} webSocketServer * @param {string} earlyDataHeader for ws 0rtt * @param {(info: string)=> void} log for ws 0rtt

(webSocketServer, earlyDataHeader, log)

 * @param {(info: string)=> void} log for ws 0rtt
 */
function makeReadableWebSocketStream(webSocketServer, earlyDataHeader, log) {
  let readableStreamCancel = false;
  const stream = new ReadableStream({
    start(controller) {
      webSocketServer.addEventListener("message", (event) => {
        if (readableStreamCancel) {
          return;
        }
        const message = event.data;
        controller.enqueue(message);
      });

      // The event means that the client closed the client -> server stream.
      // However, the server -> client stream is still open until you call close() on the server side.
      // The WebSocket protocol says that a separate close message must be sent in each direction to fully close the socket.
      webSocketServer.addEventListener("close", () => {
        // client send close, need close server
        // if stream is cancel, skip controller.close
        safeCloseWebSocket(webSocketServer);
        if (readableStreamCancel) {
          return;
        }
        controller.close();
      });
      webSocketServer.addEventListener("error", (err) => {
        log("webSocketServer has error");
        controller.error(err);
      });
      // for ws 0rtt
      const { earlyData, error } = base64ToArrayBuffer(earlyDataHeader);
      if (error) {
        controller.error(error);
      } else if (earlyData) {
        controller.enqueue(earlyData);
      }
    },

    pull(controller) {
      // if ws can stop read if stream is full, we can implement backpressure
      // https://streams.spec.whatwg.org/#example-rs-push-backpressure
    },
    cancel(reason) {
      // 1. pipe WritableStream has error, this cancel will called, so ws handle server close into here
      // 2. if readableStream is cancel, all controller.close/enqueue need skip,
      // 3. but from testing controller.error still work even if readableStream is cancel
      if (readableStreamCancel) {
        return;
      }
      log(`ReadableStream was canceled, due to ${reason}`);
      readableStreamCancel = true;
      safeCloseWebSocket(webSocketServer);
    },
  });

  return stream;
}

// https://xtls.github.io/development/protocols/vless.html