From 9d131b35b69da0c0e8ef95163fe85eeeb05db260 Mon Sep 17 00:00:00 2001
From: Terrence Cole <terrence@mozilla.com>
Date: Thu, 3 Mar 2016 10:27:57 -0800
Subject: [PATCH] Bug 956899 - Add a std::lock_guard work-alike; r=froydnj

--HG--
extra : rebase_source : c80c16798e2785f642a735bf4a24f859e202bee7
---
 js/src/jsapi-tests/testThreadingMutex.cpp |  9 +++++++
 js/src/threading/LockGuard.h              | 31 +++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 js/src/threading/LockGuard.h

diff --git a/js/src/jsapi-tests/testThreadingMutex.cpp b/js/src/jsapi-tests/testThreadingMutex.cpp
index 24962788ea4a..404cb122d827 100644
--- a/js/src/jsapi-tests/testThreadingMutex.cpp
+++ b/js/src/jsapi-tests/testThreadingMutex.cpp
@@ -6,6 +6,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "jsapi-tests/tests.h"
+#include "threading/LockGuard.h"
 #include "threading/Mutex.h"
 
 BEGIN_TEST(testThreadingMutex)
@@ -16,3 +17,11 @@ BEGIN_TEST(testThreadingMutex)
     return true;
 }
 END_TEST(testThreadingMutex)
+
+BEGIN_TEST(testThreadingLockGuard)
+{
+    js::Mutex mutex;
+    js::LockGuard<js::Mutex> guard(mutex);
+    return true;
+}
+END_TEST(testThreadingLockGuard)
diff --git a/js/src/threading/LockGuard.h b/js/src/threading/LockGuard.h
new file mode 100644
index 000000000000..41e30c23c3f1
--- /dev/null
+++ b/js/src/threading/LockGuard.h
@@ -0,0 +1,31 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef threading_LockGuard_h
+#define threading_LockGuard_h
+
+namespace js {
+
+template <typename Mutex>
+class MOZ_RAII LockGuard
+{
+  Mutex& lock;
+
+public:
+  explicit LockGuard(Mutex& aLock)
+    : lock(aLock)
+  {
+    lock.lock();
+  }
+
+  ~LockGuard() {
+    lock.unlock();
+  }
+};
+
+} // namespace js
+
+#endif // threading_LockGuard_h