streams2: Only emit 'readable' when needed

lib/_stream_readable.js

@@ -73,6 +73,7 @@ function ReadableState(options, stream) {
   // whenever we return null, then we set a flag to say
   // that we're awaiting a 'readable' event emission.
   this.needReadable = false;
+  this.emittedReadable = false;
 
   this.decoder = null;
   if (options.encoding) {
@@ -125,6 +126,9 @@ Readable.prototype.read = function(n) {
   var state = this._readableState;
   var nOrig = n;
 
+  if (typeof n !== 'number' || n > 0)
+    state.emittedReadable = false;
+
   n = howMuchToRead(n, state);
 
   // if we've ended, and we're now clear, then finish it up.
@@ -224,9 +228,13 @@ function onread(er, chunk) {
     // if we've ended and we have some data left, then emit
     // 'readable' now to make sure it gets picked up.
     if (!sync) {
-      if (state.length > 0)
+      if (state.length > 0) {
+        state.needReadable = false;
+        if (!state.emittedReadable) {
+          state.emittedReadable = true;
           this.emit('readable');
-      else
+        }
+      } else
         endReadable(this);
     }
     return;
@@ -254,8 +262,11 @@ function onread(er, chunk) {
 
   if (state.needReadable && !sync) {
     state.needReadable = false;
+    if (!state.emittedReadable) {
+      state.emittedReadable = true;
       this.emit('readable');
     }
+  }
 }
 
 // abstract method.  to be overridden in specific implementation classes.