Don't read new frames before the previous frame has been sent.

lib/units/device/plugins/screen/util/frameparser.js

@@ -1,56 +1,66 @@
-var stream = require('stream')
-var util = require('util')
-
 function FrameParser() {
   this.readFrameBytes = 0
   this.frameBodyLength = 0
-  this.frameBody = new Buffer(0)
-  stream.Transform.call(this)
+  this.frameBody = null
+  this.cursor = 0
+  this.chunk = null
 }
 
-util.inherits(FrameParser, stream.Transform)
+FrameParser.prototype.push = function(chunk) {
+  if (this.chunk) {
+    throw new Error('Must consume pending frames before pushing more chunks')
+  }
 
-FrameParser.prototype._transform = function(chunk, encoding, done) {
-  var cursor, len, bytesLeft
+  this.chunk = chunk
+}
 
-  for (cursor = 0, len = chunk.length; cursor < len;) {
+FrameParser.prototype.nextFrame = function() {
+  if (!this.chunk) {
+    return null
+  }
+
+  for (var len = this.chunk.length; this.cursor < len;) {
     if (this.readFrameBytes < 4) {
       this.frameBodyLength +=
-        (chunk[cursor] << (this.readFrameBytes * 8)) >>> 0
-      cursor += 1
+        (this.chunk[this.cursor] << (this.readFrameBytes * 8)) >>> 0
+      this.cursor += 1
       this.readFrameBytes += 1
     }
     else {
-      bytesLeft = len - cursor
+      var bytesLeft = len - this.cursor
 
       if (bytesLeft >= this.frameBodyLength) {
-        this.frameBody = Buffer.concat([
-          this.frameBody
-        , chunk.slice(cursor, cursor + this.frameBodyLength)
-        ])
+        var completeBody = this.frameBody
+          ? Buffer.concat([
+              this.frameBody
+            , this.chunk.slice(this.cursor, this.cursor + this.frameBodyLength)
+            ])
+          : this.chunk.slice(this.cursor, this.cursor + this.frameBodyLength)
 
-        this.push(this.frameBody)
-
-        cursor += this.frameBodyLength
+        this.cursor += this.frameBodyLength
         this.frameBodyLength = this.readFrameBytes = 0
-        this.frameBody = new Buffer(0)
+        this.frameBody = null
+
+        return completeBody
       }
       else {
         // @todo Consider/benchmark continuation frames to prevent
         // potential Buffer thrashing.
-        this.frameBody = Buffer.concat([
-          this.frameBody
-        , chunk.slice(cursor, len)
-        ])
+        this.frameBody = this.frameBody
+          ? Buffer.concat([this.frameBody, this.chunk.slice(this.cursor, len)])
+          : this.chunk.slice(this.cursor, len)
 
         this.frameBodyLength -= bytesLeft
         this.readFrameBytes += bytesLeft
-        cursor = len
+        this.cursor = len
       }
     }
   }
 
-  return done()
+  this.cursor = 0
+  this.chunk = null
+
+  return null
 }
 
 module.exports = FrameParser