fixup! stream: consolidate common code from readable push and unshift helper functions

Author: wa-Nadoo

lib/internal/streams/readable.js

@@ -367,18 +367,18 @@ Readable.prototype.push = function(chunk, encoding) {
   debug('push', chunk);
 
   const state = this._readableState;
-  if ((state[kState] & kEnded) !== 0) {
-    errorOrDestroy(this, new ERR_STREAM_PUSH_AFTER_EOF());
-    return false;
-  } else if ((state[kState] & (kDestroyed | kErrored)) !== 0)
-    return false;
-
   state[kState] &= ~kReading;
   if (chunk === null) {
     onEofChunk(this, state);
     return false;
   }
 
+  if ((state[kState] & kEnded) !== 0) {
+    errorOrDestroy(this, new ERR_STREAM_PUSH_AFTER_EOF());
+    return false;
+  } else if ((state[kState] & (kDestroyed | kErrored)) !== 0)
+    return false;
+
   return (state[kState] & kObjectMode) === 0 ?
     readableAddChunkPushByteMode(this, state, chunk, encoding) :
     readableAddChunkPushObjectMode(this, state, chunk, encoding);
@@ -388,18 +388,18 @@ Readable.prototype.push = function(chunk, encoding) {
 Readable.prototype.unshift = function(chunk, encoding) {
   debug('unshift', chunk);
   const state = this._readableState;
-  if ((state[kState] & kEndEmitted) !== 0) {
-    errorOrDestroy(this, new ERR_STREAM_UNSHIFT_AFTER_END_EVENT());
-    return false;
-  } else if ((state[kState] & (kDestroyed | kErrored)) !== 0)
-    return false;
-
   if (chunk === null) {
     state[kState] &= ~kReading;
     onEofChunk(this, state);
     return false;
   }
 
+  if ((state[kState] & kEndEmitted) !== 0) {
+    errorOrDestroy(this, new ERR_STREAM_UNSHIFT_AFTER_END_EVENT());
+    return false;
+  } else if ((state[kState] & (kDestroyed | kErrored)) !== 0)
+    return false;
+
   return (state[kState] & kObjectMode) === 0 ?
     readableAddChunkUnshiftByteMode(this, state, chunk, encoding) :
     readableAddChunkUnshiftObjectMode(this, state, chunk);