concat-stream - buffer object in callback is empty.

See the following piece of code.

   var  concat = require('concat-stream');
   var src = // some stream which contains non-utf-8 content for ex : shift_jis
   var dest = // it is destination stream
   var concatStream = concat(function(buffer)) {
     // buffer is empty string here. It is not readable while debugging as well.
    // I want to do some modifications in this buffer.
    dest.write(buffer);
    dest.close();
   }

On browser I see response is coming back but none of the modifications were made to the content. If I try to debug buffer is empty string in callback.

Begin with the concat-stream callback shown in the issue and reproduce it using the reported non-UTF-8 stream case. Compare the callback value with the data written to dest and verify whether modifications are preserved in the browser scenario; the issue is done when the callback no longer yields the reported empty value.