WebSocket client: respect write capacity during upgrade

examples/io/tcp/websocketclient/websocketclient.js

@@ -541,11 +541,24 @@ class WebSocketClient {
 
 				message.push("", "");
 
-				//@@ if headers exceed count, send in pieces
-				message = ArrayBuffer.fromString(message.join("\r\n"));
+				options.request = new Uint8Array(ArrayBuffer.fromString(message.join("\r\n")));
+				this.#state = "sendRequest";
+				}
+			case "sendRequest": {
+				const options = this.#options;
+				const request = options.request;
+				const use = Math.min(this.#writable, request.byteLength);
+				if (!use)
+					break;
+				const message = request.subarray(0, use);
 				this.#writable = this.#socket.write(message); 
 
-				this.#state = "receiveStatus"
+				if (use < request.byteLength) {
+					options.request = request.subarray(use);
+					break;
+				}
+				delete options.request;
+				this.#state = "receiveStatus";
 				this.#line = "";
 				options.flags = 0;
 				this.#socket.format = NumberFormat;

tests/modules/network/websocket/client/request-backpressure.js

@@ -0,0 +1,49 @@
+/*---
+description: WebSocket upgrade request respects socket write capacity
+flags: [async, module]
+---*/
+import Timer from "timer";
+import WebSocketClient from "embedded:network/websocket/client";
+
+const capacity = 64;
+let client;
+class Resolver {
+	resolve(options) {
+		options.onResolved(options.host, "127.0.0.1");
+	}
+}
+class Socket {
+	#options;
+	static writes = 0;
+
+	constructor(options) {
+		this.#options = options;
+		Timer.set(() => options.onWritable(capacity));
+	}
+	write(buffer) {
+		assert(buffer.byteLength <= capacity, "write exceeds reported capacity");
+		Socket.writes++;
+		const bytes = new Uint8Array(buffer.buffer, buffer.byteOffset, buffer.byteLength);
+		const length = bytes.byteLength;
+		if ((length >= 4) && (13 === bytes[length - 4]) && (10 === bytes[length - 3]) &&
+			(13 === bytes[length - 2]) && (10 === bytes[length - 1])) {
+			Timer.set(() => $DO(() => {
+				assert(Socket.writes > 1, "request should be split across writes");
+				client.close();
+			})());
+		}
+		else
+			Timer.set(() => this.#options.onWritable(capacity));
+		return 0;
+	}
+	close() {}
+	set format(_) {}
+}
+$TESTMC.timeout(1_000);
+client = new WebSocketClient({
+	host: "example.com",
+	headers: [["X-Padding", "x".repeat(160)]],
+	dns: {io: Resolver},
+	socket: {io: Socket},
+	onError() { $DONE("unexpected error"); }
+});

tools/testmc/manifest.json

@@ -8,6 +8,7 @@
 		"$(MODULES)/data/base64/manifest.json",
 		"$(MODULES)/data/crc/manifest.json",
 		"$(MODULES)/data/hex/manifest.json",
+		"$(MODULES)/data/logical/manifest.json",
 		"$(MODULES)/data/qrcode/manifest.json",
 		"$(MODULES)/data/text/decoder/manifest.json",
 		"$(MODULES)/data/text/encoder/manifest.json",
@@ -42,6 +43,7 @@
 		"commodetto/*": "$(MODULES)/commodetto/commodettoPocoBlit",
 		"commodetto/cfe": "$(MODULES)/commodetto/cfeBMF",
 		"commodetto/checksumOut": "./commodettoChecksumOut",
+		"embedded:network/websocket/client": "$(MODDABLE)/examples/io/tcp/websocketclient/websocketclient",
         "piu/Sound": "$(MODULES)/piu/MC/piuSound"
 	},
 	"preload": [