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'use strict';
const { Duplex } = require('stream');
/**
* Emits the `'close'` event on a stream.
*
* @param {Duplex} stream The stream.
* @private
*/
function emitClose(stream) {
stream.emit('close');
}
/**
* The listener of the `'end'` event.
*
* @private
*/
function duplexOnEnd() {
if (!this.destroyed && this._writableState.finished) {
this.destroy();
}
}
/**
* The listener of the `'error'` event.
*
* @param {Error} err The error
* @private
*/
function duplexOnError(err) {
this.removeListener('error', duplexOnError);
this.destroy();
if (this.listenerCount('error') === 0) {
// Do not suppress the throwing behavior.
this.emit('error', err);
}
}
/**
* Wraps a `WebSocket` in a duplex stream.
*
* @param {WebSocket} ws The `WebSocket` to wrap
* @param {Object} [options] The options for the `Duplex` constructor
* @return {Duplex} The duplex stream
* @public
*/
function createWebSocketStream(ws, options) {
let terminateOnDestroy = true;
const duplex = new Duplex({
...options,
autoDestroy: false,
emitClose: false,
objectMode: false,
writableObjectMode: false
});
ws.on('message', function message(msg, isBinary) {
const data =
!isBinary && duplex._readableState.objectMode ? msg.toString() : msg;
if (!duplex.push(data)) ws.pause();
});
ws.once('error', function error(err) {
if (duplex.destroyed) return;
// Prevent `ws.terminate()` from being called by `duplex._destroy()`.
//
// - If the `'error'` event is emitted before the `'open'` event, then
// `ws.terminate()` is a noop as no socket is assigned.
// - Otherwise, the error is re-emitted by the listener of the `'error'`
// event of the `Receiver` object. The listener already closes the
// connection by calling `ws.close()`. This allows a close frame to be
// sent to the other peer. If `ws.terminate()` is called right after this,
// then the close frame might not be sent.
terminateOnDestroy = false;
duplex.destroy(err);
});
ws.once('close', function close() {
if (duplex.destroyed) return;
duplex.push(null);
});
duplex._destroy = function (err, callback) {
if (ws.readyState === ws.CLOSED) {
callback(err);
process.nextTick(emitClose, duplex);
return;
}
let called = false;
ws.once('error', function error(err) {
called = true;
callback(err);
});
ws.once('close', function close() {
if (!called) callback(err);
process.nextTick(emitClose, duplex);
});
if (terminateOnDestroy) ws.terminate();
};
duplex._final = function (callback) {
if (ws.readyState === ws.CONNECTING) {
ws.once('open', function open() {
duplex._final(callback);
});
return;
}
// If the value of the `_socket` property is `null` it means that `ws` is a
// client websocket and the handshake failed. In fact, when this happens, a
// socket is never assigned to the websocket. Wait for the `'error'` event
// that will be emitted by the websocket.
if (ws._socket === null) return;
if (ws._socket._writableState.finished) {
callback();
if (duplex._readableState.endEmitted) duplex.destroy();
} else {
ws._socket.once('finish', function finish() {
// `duplex` is not destroyed here because the `'end'` event will be
// emitted on `duplex` after this `'finish'` event. The EOF signaling
// `null` chunk is, in fact, pushed when the websocket emits `'close'`.
callback();
});
ws.close();
}
};
duplex._read = function () {
if (ws.isPaused) ws.resume();
};
duplex._write = function (chunk, encoding, callback) {
if (ws.readyState === ws.CONNECTING) {
ws.once('open', function open() {
duplex._write(chunk, encoding, callback);
});
return;
}
ws.send(chunk, callback);
};
duplex.on('end', duplexOnEnd);
duplex.on('error', duplexOnError);
return duplex;
}
module.exports = createWebSocketStream;
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