feat(websocket): only consume necessary bytes

lib/websocket/constants.js

@@ -38,11 +38,14 @@ const parserStates = {
   READ_DATA: 4
 }
 
+const emptyBuffer = Buffer.allocUnsafe(0)
+
 module.exports = {
   uid,
   staticPropertyDescriptors,
   states,
   opcodes,
   maxUnsigned16Bit,
-  parserStates
+  parserStates,
+  emptyBuffer
 }

lib/websocket/receiver.js

@@ -2,11 +2,16 @@
 
 const { Writable } = require('stream')
 const diagnosticsChannel = require('diagnostics_channel')
-const { parserStates, opcodes, states } = require('./constants')
+const { parserStates, opcodes, states, emptyBuffer } = require('./constants')
 const { kReadyState, kSentClose, kResponse, kReceivedClose } = require('./symbols')
 const { isValidStatusCode, failWebsocketConnection, websocketMessageReceived } = require('./util')
 const { WebsocketFrameSend } = require('./frame')
 
+// This code was influenced by ws released under the MIT license.
+// Copyright (c) 2011 Einar Otto Stangvik <[email protected]>
+// Copyright (c) 2013 Arnout Kazemier and contributors
+// Copyright (c) 2016 Luigi Pinca and contributors
+
 const channels = {}
 channels.ping = diagnosticsChannel.channel('undici:websocket:ping')
 channels.pong = diagnosticsChannel.channel('undici:websocket:pong')
@@ -49,7 +54,7 @@ class ByteParser extends Writable {
         return callback()
       }
 
-      const buffer = Buffer.concat(this.#buffers, this.#byteOffset)
+      const buffer = this.consume(2)
 
       this.#info.fin = (buffer[0] & 0x80) !== 0
       this.#info.opcode = buffer[0] & 0x0F
@@ -96,7 +101,7 @@ class ByteParser extends Writable {
           return
         }
 
-        const body = buffer.subarray(2, payloadLength + 2)
+        const body = this.consume(payloadLength)
 
         this.#info.closeInfo = this.parseCloseBody(false, body)
 
@@ -125,9 +130,6 @@ class ByteParser extends Writable {
         this.ws[kReadyState] = states.CLOSING
         this.ws[kReceivedClose] = true
 
-        this.#buffers = [buffer.subarray(2 + payloadLength)]
-        this.#byteOffset -= 2 + payloadLength
-
         this.end()
 
         return
@@ -137,8 +139,9 @@ class ByteParser extends Writable {
         // A Pong frame sent in response to a Ping frame must have identical
         // "Application data"
 
+        const body = this.consume(payloadLength)
+
         if (!this.ws[kReceivedClose]) {
-          const body = payloadLength === 0 ? undefined : buffer.subarray(2, payloadLength + 2)
           const frame = new WebsocketFrameSend(body)
 
           this.ws[kResponse].socket.write(frame.createFrame(opcodes.PONG))
@@ -150,8 +153,6 @@ class ByteParser extends Writable {
           }
         }
 
-        this.#buffers = [buffer.subarray(2 + payloadLength)]
-        this.#byteOffset -= 2 + payloadLength
         this.#state = parserStates.INFO
 
         if (this.#byteOffset > 0) {
@@ -165,72 +166,50 @@ class ByteParser extends Writable {
         // unidirectional heartbeat.  A response to an unsolicited Pong frame is
         // not expected.
 
+        const body = this.consume(payloadLength)
+
         if (channels.pong.hasSubscribers) {
           channels.pong.publish({
-            payload: buffer.subarray(2, payloadLength + 2)
+            payload: body
           })
         }
 
-        this.#buffers = [buffer.subarray(2 + payloadLength)]
-        this.#byteOffset -= 2 + payloadLength
-
         if (this.#byteOffset > 0) {
           return this.run(callback)
         } else {
           callback()
           return
         }
       }
-
-      // TODO: handle control frames here. Since they are unfragmented, and can
-      // be sent in the middle of other frames, we shouldn't parse them as normal.
-
-      this.#buffers = [buffer.subarray(2)]
-      this.#byteOffset -= 2
     } else if (this.#state === parserStates.PAYLOADLENGTH_16) {
       if (this.#byteOffset < 2) {
         return callback()
       }
 
-      const buffer = Buffer.concat(this.#buffers, this.#byteOffset)
+      const buffer = this.consume(2)
 
-      // TODO: optimize this
-      this.#info.payloadLength = buffer.subarray(0, 2).readUInt16BE(0)
+      this.#info.payloadLength = buffer.readUInt16BE(0)
       this.#state = parserStates.READ_DATA
-
-      this.#buffers = [buffer.subarray(2)]
-      this.#byteOffset -= 2
     } else if (this.#state === parserStates.PAYLOADLENGTH_64) {
       if (this.#byteOffset < 8) {
         return callback()
       }
 
-      const buffer = Buffer.concat(this.#buffers, this.#byteOffset)
+      const buffer = this.consume(8)
 
       // TODO: optimize this
-      this.#info.payloadLength = buffer.subarray(0, 8).readBigUint64BE(0)
+      this.#info.payloadLength = buffer.readBigUint64BE(0)
       this.#state = parserStates.READ_DATA
-
-      this.#buffers = [buffer.subarray(8)]
-      this.#byteOffset -= 8
     } else if (this.#state === parserStates.READ_DATA) {
       if (this.#byteOffset < this.#info.payloadLength) {
         // If there is still more data in this chunk that needs to be read
         return callback()
       } else if (this.#byteOffset >= this.#info.payloadLength) {
         // If the server sent multiple frames in a single chunk
-        const buffer = Buffer.concat(this.#buffers, this.#byteOffset)
 
-        const body = buffer.subarray(0, this.#info.payloadLength)
-        this.#fragments.push(body)
+        const body = this.consume(this.#info.payloadLength)
 
-        if (this.#byteOffset > this.#info.payloadLength) {
-          this.#buffers = [buffer.subarray(body.length)]
-          this.#byteOffset -= body.length
-        } else {
-          this.#buffers.length = 0
-          this.#byteOffset = 0
-        }
+        this.#fragments.push(body)
 
         // If the frame is unfragmented, or a fragmented frame was terminated,
         // a message was received
@@ -254,6 +233,48 @@ class ByteParser extends Writable {
     }
   }
 
+  /**
+   * Take n bytes from the buffered Buffers
+   * @param {number} n
+   * @returns {Buffer|null}
+   */
+  consume (n) {
+    if (n > this.#byteOffset) {
+      return null
+    } else if (n === 0) {
+      return emptyBuffer
+    }
+
+    if (this.#buffers[0].length === n) {
+      this.#byteOffset -= this.#buffers[0].length
+      return this.#buffers.shift()
+    }
+
+    const buffer = Buffer.allocUnsafe(n)
+    let offset = 0
+
+    while (offset !== n) {
+      const next = this.#buffers[0]
+      const { length } = next
+
+      if (length + offset === n) {
+        buffer.set(this.#buffers.shift(), offset)
+        break
+      } else if (length + offset > n) {
+        buffer.set(next.subarray(0, n - offset), offset)
+        this.#buffers[0] = next.subarray(n - offset)
+        break
+      } else {
+        buffer.set(this.#buffers.shift(), offset)
+        offset += next.length
+      }
+    }
+
+    this.#byteOffset -= n
+
+    return buffer
+  }
+
   parseCloseBody (onlyCode, data) {
     // https://datatracker.ietf.org/doc/html/rfc6455#section-7.1.5
     /** @type {number|undefined} */

lib/websocket/websocket.js

@@ -3,7 +3,7 @@
 const { webidl } = require('../fetch/webidl')
 const { DOMException } = require('../fetch/constants')
 const { URLSerializer } = require('../fetch/dataURL')
-const { staticPropertyDescriptors, states, opcodes } = require('./constants')
+const { staticPropertyDescriptors, states, opcodes, emptyBuffer } = require('./constants')
 const {
   kWebSocketURL,
   kReadyState,
@@ -207,7 +207,7 @@ class WebSocket extends EventTarget {
         // the body MAY contain UTF-8-encoded data with value /reason/
         frame.frameData.write(reason, 2, 'utf-8')
       } else {
-        frame.frameData = Buffer.alloc(0)
+        frame.frameData = emptyBuffer
       }
 
       /** @type {import('stream').Duplex} */