From 4a87abb8e85986196aa36e2f95a633573fdf947b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Linus=20Unneb=C3=A4ck?= <linus@folkdatorn.se>
Date: Mon, 1 Aug 2016 21:31:16 +0200
Subject: [PATCH] fs: add bytesRead to ReadStream

Add a property named bytesRead that exposes how many bytes that have
currently been read from the file. This brings consistency with
WriteStream that has bytesWritten and net.Socket which have both
bytesRead and bytesWritten.

Fixes: https://github.com/nodejs/node/issues/#7938
PR-URL: https://github.com/nodejs/node/pull/7942
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
---
 doc/api/fs.md                        |  7 +++++++
 lib/fs.js                            |  5 ++++-
 test/parallel/test-fs-read-stream.js | 12 ++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/doc/api/fs.md b/doc/api/fs.md
index 32ffed51c07..ab8c8a92bdf 100644
--- a/doc/api/fs.md
+++ b/doc/api/fs.md
@@ -181,6 +181,13 @@ added: v0.1.93
 Emitted when the `ReadStream`'s underlying file descriptor has been closed
 using the `fs.close()` method.
 
+### readStream.bytesRead
+<!-- YAML
+added: REPLACEME
+-->
+
+The number of bytes read so far.
+
 ### readStream.path
 <!-- YAML
 added: v0.1.93
diff --git a/lib/fs.js b/lib/fs.js
index e3bfdabe885..eb2587296a9 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -1679,6 +1679,7 @@ function ReadStream(path, options) {
   this.end = options.end;
   this.autoClose = options.autoClose === undefined ? true : options.autoClose;
   this.pos = undefined;
+  this.bytesRead = 0;
 
   if (this.start !== undefined) {
     if (typeof this.start !== 'number') {
@@ -1774,8 +1775,10 @@ ReadStream.prototype._read = function(n) {
       self.emit('error', er);
     } else {
       var b = null;
-      if (bytesRead > 0)
+      if (bytesRead > 0) {
+        self.bytesRead += bytesRead;
         b = thisPool.slice(start, start + bytesRead);
+      }
 
       self.push(b);
     }
diff --git a/test/parallel/test-fs-read-stream.js b/test/parallel/test-fs-read-stream.js
index 98a316e60e4..7b133022511 100644
--- a/test/parallel/test-fs-read-stream.js
+++ b/test/parallel/test-fs-read-stream.js
@@ -10,13 +10,18 @@ var rangeFile = path.join(common.fixturesDir, 'x.txt');
 var callbacks = { open: 0, end: 0, close: 0 };
 
 var paused = false;
+var bytesRead = 0;
 
 var file = fs.ReadStream(fn);
+var fileSize = fs.statSync(fn).size;
+
+assert.strictEqual(file.bytesRead, 0);
 
 file.on('open', function(fd) {
   file.length = 0;
   callbacks.open++;
   assert.equal('number', typeof fd);
+  assert.strictEqual(file.bytesRead, 0);
   assert.ok(file.readable);
 
   // GH-535
@@ -31,6 +36,9 @@ file.on('data', function(data) {
   assert.ok(!paused);
   file.length += data.length;
 
+  bytesRead += data.length;
+  assert.strictEqual(file.bytesRead, bytesRead);
+
   paused = true;
   file.pause();
 
@@ -42,11 +50,15 @@ file.on('data', function(data) {
 
 
 file.on('end', function(chunk) {
+  assert.strictEqual(bytesRead, fileSize);
+  assert.strictEqual(file.bytesRead, fileSize);
   callbacks.end++;
 });
 
 
 file.on('close', function() {
+  assert.strictEqual(bytesRead, fileSize);
+  assert.strictEqual(file.bytesRead, fileSize);
   callbacks.close++;
 
   //assert.equal(fs.readFileSync(fn), fileContent);