Add a portable wrapper for reader-writer locks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73545 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/System/RWMutex.h

@@ -0,0 +1,84 @@
+//===- RWMutex.h - Reader/Writer Mutual Exclusion Lock ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the llvm::sys::RWMutex class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SYSTEM_MUTEX_H
+#define LLVM_SYSTEM_MUTEX_H
+
+namespace llvm
+{
+  namespace sys
+  {
+    /// @brief Platform agnostic Mutex class.
+    class RWMutex
+    {
+    /// @name Constructors
+    /// @{
+    public:
+
+      /// Initializes the lock but doesn't acquire it.
+      /// @brief Default Constructor.
+      explicit RWMutex();
+
+      /// Releases and removes the lock
+      /// @brief Destructor
+      ~RWMutex();
+
+    /// @}
+    /// @name Methods
+    /// @{
+    public:
+
+      /// Attempts to unconditionally acquire the lock in reader mode. If the
+      /// lock is held by a writer, this method will wait until it can acquire
+      /// the lock. 
+      /// @returns false if any kind of error occurs, true otherwise.
+      /// @brief Unconditionally acquire the lock in reader mode.
+      bool reader_acquire();
+
+      /// Attempts to release the lock in reader mode.
+      /// @returns false if any kind of error occurs, true otherwise.
+      /// @brief Unconditionally release the lock in reader mode.
+      bool reader_release();
+
+      /// Attempts to unconditionally acquire the lock in reader mode. If the
+      /// lock is held by any readers, this method will wait until it can
+      /// acquire the lock. 
+      /// @returns false if any kind of error occurs, true otherwise.
+      /// @brief Unconditionally acquire the lock in writer mode.
+      bool writer_acquire();
+
+      /// Attempts to release the lock in writer mode.
+      /// @returns false if any kind of error occurs, true otherwise.
+      /// @brief Unconditionally release the lock in write mode.
+      bool writer_release();
+
+    //@}
+    /// @name Platform Dependent Data
+    /// @{
+    private:
+#ifdef ENABLE_THREADS
+      void* data_; ///< We don't know what the data will be
+#endif
+
+    /// @}
+    /// @name Do Not Implement
+    /// @{
+    private:
+      RWMutex(const RWMutex & original);
+      void operator=(const RWMutex &);
+    /// @}
+    };
+  }
+}
+
+#endif