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//===-- Support/MutexGuard.h - Acquire/Release Mutex In Scope ---*- C++ -*-===//
//                     The LLVM Compiler Infrastructure
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// This file defines a guard for a block of code that ensures a Mutex is locked
// upon construction and released upon destruction.


#include <llvm/System/Mutex.h>

namespace llvm {
  /// Instances of this class acquire a given Mutex Lock when constructed and
  /// hold that lock until destruction. The intention is to instantiate one of
  /// these on the stack at the top of some scope to be assured that C++
  /// destruction of the object will always release the Mutex and thus avoid
  /// a host of nasty multi-threading problems in the face of exceptions, etc.
  /// @brief Guard a section of code with a Mutex.
  class MutexGuard {
    sys::Mutex &M;
    MutexGuard(const MutexGuard &);    // DO NOT IMPLEMENT
    void operator=(const MutexGuard &); // DO NOT IMPLEMENT
    MutexGuard(sys::Mutex &m) : M(m) { M.acquire(); }
    ~MutexGuard() { M.release(); }
    /// holds - Returns true if this locker instance holds the specified lock.
    /// This is mostly used in assertions to validate that the correct mutex
    /// is held.
    bool holds(const sys::Mutex& lock) const { return &M == &lock; }