From 460a501d3030e503370f9e3a46d2b4f625668a52 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 #7938
---
 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 1984b5642e305b..dfdb6bf29811d5 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 e3bfdabe885734..eb2587296a9295 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 98a316e60e4a02..7b133022511910 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);