stream: add bytesRead property for readable

Add a bytesRead property for readable is
useful in some use cases.

When user want know how many bytes read of
readable, need to caculate it in userland.
If encoding is specificed, get the value is
very slowly.

PR-URL: https://github.com/nodejs/node/pull/4372
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
index bdc263d6ef..8cad1f1a37 100644
--- a/lib/_stream_readable.js
+++ b/lib/_stream_readable.js
@@ -83,6 +83,8 @@ function Readable(options) {
 
   this._readableState = new ReadableState(options, this);
 
+  this.bytesRead = 0;
+
   // legacy
   this.readable = true;
 
@@ -135,6 +137,7 @@ function readableAddChunk(stream, state, chunk, encoding, addToFront) {
       var e = new Error('stream.unshift() after end event');
       stream.emit('error', e);
     } else {
+      stream.bytesRead += state.objectMode ? 0 : chunk.length;
       if (state.decoder && !addToFront && !encoding)
         chunk = state.decoder.write(chunk);