Add utility for reading varint32-delimited streams.

lib/wire/messagestream.js

@@ -0,0 +1,52 @@
+var util = require('util')
+var stream = require('stream')
+
+function MessageStream() {
+  stream.Transform.call(this)
+  this._length = 0
+  this._lengthIndex = 0
+  this._readingLength = true
+  this._buffer = new Buffer(0)
+}
+
+util.inherits(MessageStream, stream.Transform)
+
+MessageStream.prototype._transform = function(chunk, encoding, done) {
+  this._buffer = Buffer.concat([this._buffer, chunk])
+
+  var lo = 0
+  var hi = this._buffer.length
+
+  while (lo < hi) {
+    if (this._readingLength) {
+      while (lo < hi) {
+        var byte = this._buffer[lo++]
+        if (byte & (1 << 7)) {
+          this._length += (byte & 0x7f) << (7 * this._lengthIndex)
+          this._lengthIndex += 1
+          this._readingLength = true
+        }
+        else {
+          this._length += (byte & 0x7f) << (7 * this._lengthIndex)
+          this._lengthIndex = 0
+          this._readingLength = false
+          break
+        }
+      }
+    }
+
+    if (!this._readingLength && lo + this._length <= hi) {
+      this.push(chunk.slice(lo, lo + this._length))
+      lo += this._length
+      this._length = 0
+      this._readingLength = true
+    }
+    else {
+      break
+    }
+  }
+
+  done()
+}
+
+module.exports = MessageStream