Factor out ScopedRWLock into its own header

Bug: http://b/78026329
Test: bionic unit tests
Change-Id: I1d1276da835bc8ecac7a7abb714d639a1ee58007
diff --git a/libc/private/ScopedRWLock.h b/libc/private/ScopedRWLock.h
new file mode 100644
index 0000000..f034505
--- /dev/null
+++ b/libc/private/ScopedRWLock.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <pthread.h>
+
+#include "private/bionic_macros.h"
+
+template <bool write> class ScopedRWLock {
+ public:
+  explicit ScopedRWLock(pthread_rwlock_t* rwlock) : rwlock_(rwlock) {
+    (write ? pthread_rwlock_wrlock : pthread_rwlock_rdlock)(rwlock_);
+  }
+
+  ~ScopedRWLock() {
+    pthread_rwlock_unlock(rwlock_);
+  }
+
+ private:
+  pthread_rwlock_t* rwlock_;
+  BIONIC_DISALLOW_IMPLICIT_CONSTRUCTORS(ScopedRWLock);
+};
+
+typedef ScopedRWLock<true> ScopedWriteLock;
+typedef ScopedRWLock<false> ScopedReadLock;