map charsWritten to fast buffer

lib/buffer.js

@@ -211,23 +211,33 @@ Buffer.prototype.write = function write (string, offset, encoding) {
   // Make sure we are not going to overflow
   var maxLength = this.length - offset;
 
+  var ret;
   switch (encoding) {
     case 'utf8':
     case 'utf-8':
-      return this.parent.utf8Write(string, this.offset + offset, maxLength);
+      ret = this.parent.utf8Write(string, this.offset + offset, maxLength);
+      break;
 
     case 'ascii':
-      return this.parent.asciiWrite(string, this.offset + offset, maxLength);
+      ret = this.parent.asciiWrite(string, this.offset + offset, maxLength);
+      break;
 
     case 'binary':
-      return this.parent.binaryWrite(string, this.offset + offset, maxLength);
+      ret = this.parent.binaryWrite(string, this.offset + offset, maxLength);
+      break;
 
     case 'base64':
-      return this.parent.base64Write(string, this.offset + offset, maxLength);
+      // Warning: maxLength not taken into account in base64Write
+      ret = this.parent.base64Write(string, this.offset + offset, maxLength);
+      break;
 
     default:
       throw new Error('Unknown encoding');
   }
+
+  Buffer._charsWritten = SlowBuffer._charsWritten;
+
+  return ret;
 };