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: #4372
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/stream.markdown

@@ -250,6 +250,11 @@ readable: null
 end
 ```
 
+
+#### readable.bytesRead
+
+The amount of read bytes. If `objectMode` is `true`, the value is 0 always.
+
 #### readable.isPaused()
 
 * Return: `Boolean`

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);
 

lib/net.js

@@ -91,7 +91,6 @@ exports._normalizeConnectArgs = normalizeConnectArgs;
 // called when creating new Socket, or when re-using a closed Socket
 function initSocketHandle(self) {
   self.destroyed = false;
-  self.bytesRead = 0;
   self._bytesDispatched = 0;
   self._sockname = null;
 
@@ -515,10 +514,6 @@ function onread(nread, buffer) {
     // will prevent this from being called again until _read() gets
     // called again.
 
-    // if it's not enough data, we'll just call handle.readStart()
-    // again right away.
-    self.bytesRead += nread;
-
     // Optimization: emit the original buffer with end points
     var ret = self.push(buffer);
 

test/parallel/test-stream2-readable-bytesread.js

@@ -0,0 +1,119 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const Readable = require('stream').Readable;
+const Duplex = require('stream').Duplex;
+const Transform = require('stream').Transform;
+
+(function() {
+  const readable = new Readable({
+    read: function(n) {
+      var i = this._index++;
+      if (i > this._max)
+        this.push(null);
+      else
+        this.push(new Buffer('a'));
+    }
+  });
+
+  readable._max = 1000;
+  readable._index = 1;
+
+  var total = 0;
+  readable.on('data', function(chunk) {
+    total += chunk.length;
+  });
+
+  readable.on('end', function() {
+    assert.equal(total, readable.bytesRead);
+  });
+})();
+
+(function() {
+  const readable = new Readable({
+    read: function(n) {
+      var i = this._index++;
+      if (i > this._max)
+        this.push(null);
+      else
+        this.push(new Buffer('a'));
+    }
+  });
+
+  readable._max = 1000;
+  readable._index = 1;
+
+  var total = 0;
+  readable.setEncoding('utf8');
+  readable.on('data', function(chunk) {
+    total += Buffer.byteLength(chunk);
+  });
+
+  readable.on('end', function() {
+    assert.equal(total, readable.bytesRead);
+  });
+})();
+
+(function() {
+  const duplex = new Duplex({
+    read: function(n) {
+      var i = this._index++;
+      if (i > this._max)
+        this.push(null);
+      else
+        this.push(new Buffer('a'));
+    },
+    write: function(chunk, encoding, next) {
+      next();
+    }
+  });
+
+  duplex._max = 1000;
+  duplex._index = 1;
+
+  var total = 0;
+  duplex.setEncoding('utf8');
+  duplex.on('data', function(chunk) {
+    total += Buffer.byteLength(chunk);
+  });
+
+  duplex.on('end', function() {
+    assert.equal(total, duplex.bytesRead);
+  });
+})();
+
+(function() {
+  const readable = new Readable({
+    read: function(n) {
+      var i = this._index++;
+      if (i > this._max)
+        this.push(null);
+      else
+        this.push(new Buffer('{"key":"value"}'));
+    }
+  });
+  readable._max = 1000;
+  readable._index = 1;
+
+  const transform = new Transform({
+    readableObjectMode : true,
+    transform: function(chunk, encoding, next) {
+      next(null, JSON.parse(chunk));
+    },
+    flush: function(done) {
+      done();
+    }
+  });
+
+  var total = 0;
+  readable.on('data', function(chunk) {
+    total += chunk.length;
+  });
+
+  transform.on('end', function() {
+    assert.equal(0, transform.bytesRead);
+    assert.equal(total, readable.bytesRead);
+  });
+  readable.pipe(transform);
+})();