Parser: don't set _read() for body until it's needed (push() returns false)

This fixes a problem where _read() was firing before the parsing function exited, causing the wrong data to be pulled in from the socket stream.

lib/Parser.js

@@ -35,14 +35,14 @@ function Parser(stream, debug) {
   this.setStream(stream);
 
   var self = this;
-  function cb() {
-    if (self._literallen > 0)
+  this._cbReadable = function() {
+    if (self._literallen > 0 && !self._body)
       self._tryread(self._literallen);
     else
       self._tryread();
   }
-  this._stream.on('readable', cb);
-  process.nextTick(cb);
+  this._stream.on('readable', this._cbReadable);
+  process.nextTick(this._cbReadable);
 }
 inherits(Parser, EventEmitter);
 
@@ -75,8 +75,10 @@ Parser.prototype._parse = function(data) {
       } else {
         this._literallen -= datalen;
         var r = body.push(data);
-        if (!r && this._literallen > 0)
+        if (!r && this._literallen > 0) {
+          body._read = this._cbReadable;
           return;
+        }
         i = datalen;
       }
       if (this._literallen === 0) {
@@ -166,9 +168,7 @@ Parser.prototype._resUntagged = function() {
     var which = m[1], size = parseInt(m[2], 10);
     this._literallen = size;
     this._body = new ReadableStream();
-    this._body._read = function bodyread(n) {
-      self._tryread();
-    };
+    this._body._read = EMPTY_READCB;
     m = RE_SEQNO.exec(this._buffer);
     this._buffer = this._buffer.replace(RE_BODYLITERAL, '');
     this.emit('body', this._body, {