Additional WebSocket send tests to cover all payload size categories (n…

…odejs#2149)

* Fixed bug in 16-bit frame length when buffer is a subarray

I was just bitten by this issue. Because buffer could be a subarray, the `byteOffset` and `byteLength` arguments to `new DataView()` are required, otherwise the length value may be written at the wrong offset.

Alternatively, it looks like it would be simpler (and it also works) to replace the patched line with `buffer.writeUInt16BE(bodyLength, 2)`.

* Switched 16-bit length-writing fix to use Buffer.writeUInt16 instead of DataView.setUint16, and added a test for the fix

* Added WebSocket send tests for the two previously-untested payload size categories

test/websocket/send.js

@@ -5,7 +5,11 @@ const { WebSocketServer } = require('ws')
 const { Blob } = require('buffer')
 const { WebSocket } = require('../..')
 
-test('Sending > 2^16 bytes', (t) => {
+// the following three tests exercise different code paths because of the three
+// different ways a payload length may be specified in a WebSocket frame
+// (https://datatracker.ietf.org/doc/html/rfc6455#section-5.2)
+
+test('Sending >= 2^16 bytes', (t) => {
   t.plan(3)
 
   const server = new WebSocketServer({ port: 0 })
@@ -34,6 +38,64 @@ test('Sending > 2^16 bytes', (t) => {
   })
 })
 
+test('Sending >= 126, < 2^16 bytes', (t) => {
+  t.plan(3)
+
+  const server = new WebSocketServer({ port: 0 })
+
+  server.on('connection', (ws) => {
+    ws.on('message', (m, isBinary) => {
+      ws.send(m, { binary: isBinary })
+    })
+  })
+
+  const payload = Buffer.allocUnsafe(126).fill('Hello')
+
+  const ws = new WebSocket(`ws://localhost:${server.address().port}`)
+
+  ws.addEventListener('open', () => {
+    ws.send(payload)
+  })
+
+  ws.addEventListener('message', async ({ data }) => {
+    t.type(data, Blob)
+    t.equal(data.size, payload.length)
+    t.same(Buffer.from(await data.arrayBuffer()), payload)
+
+    ws.close()
+    server.close()
+  })
+})
+
+test('Sending < 126 bytes', (t) => {
+  t.plan(3)
+
+  const server = new WebSocketServer({ port: 0 })
+
+  server.on('connection', (ws) => {
+    ws.on('message', (m, isBinary) => {
+      ws.send(m, { binary: isBinary })
+    })
+  })
+
+  const payload = Buffer.allocUnsafe(125).fill('Hello')
+
+  const ws = new WebSocket(`ws://localhost:${server.address().port}`)
+
+  ws.addEventListener('open', () => {
+    ws.send(payload)
+  })
+
+  ws.addEventListener('message', async ({ data }) => {
+    t.type(data, Blob)
+    t.equal(data.size, payload.length)
+    t.same(Buffer.from(await data.arrayBuffer()), payload)
+
+    ws.close()
+    server.close()
+  })
+})
+
 test('Sending data after close', (t) => {
   t.plan(2)