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       1             : //===- Support/UniqueLock.h - Acquire/Release Mutex In Scope ----*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // This file defines a guard for a block of code that ensures a Mutex is locked
      11             : // upon construction and released upon destruction.
      12             : //
      13             : //===----------------------------------------------------------------------===//
      14             : 
      15             : #ifndef LLVM_SUPPORT_UNIQUE_LOCK_H
      16             : #define LLVM_SUPPORT_UNIQUE_LOCK_H
      17             : 
      18             : #include <cassert>
      19             : 
      20             : namespace llvm {
      21             : 
      22             :   /// A pared-down imitation of std::unique_lock from C++11. Contrary to the
      23             :   /// name, it's really more of a wrapper for a lock. It may or may not have
      24             :   /// an associated mutex, which is guaranteed to be locked upon creation
      25             :   /// and unlocked after destruction. unique_lock can also unlock the mutex
      26             :   /// and re-lock it freely during its lifetime.
      27             :   /// Guard a section of code with a mutex.
      28             :   template<typename MutexT>
      29             :   class unique_lock {
      30             :     MutexT *M = nullptr;
      31             :     bool locked = false;
      32             : 
      33             :   public:
      34             :     unique_lock() = default;
      35             :     explicit unique_lock(MutexT &m) : M(&m), locked(true) { M->lock(); }
      36             :     unique_lock(const unique_lock &) = delete;
      37             :      unique_lock &operator=(const unique_lock &) = delete;
      38             : 
      39           0 :     void operator=(unique_lock &&o) {
      40           0 :       if (owns_lock())
      41           0 :         M->unlock();
      42           0 :       M = o.M;
      43           0 :       locked = o.locked;
      44           0 :       o.M = nullptr;
      45           0 :       o.locked = false;
      46           0 :     }
      47             : 
      48           6 :     ~unique_lock() { if (owns_lock()) M->unlock(); }
      49             : 
      50             :     void lock() {
      51             :       assert(!locked && "mutex already locked!");
      52             :       assert(M && "no associated mutex!");
      53             :       M->lock();
      54             :       locked = true;
      55             :     }
      56             : 
      57           0 :     void unlock() {
      58             :       assert(locked && "unlocking a mutex that isn't locked!");
      59             :       assert(M && "no associated mutex!");
      60           0 :       M->unlock();
      61           0 :       locked = false;
      62           0 :     }
      63             : 
      64           0 :     bool owns_lock() { return locked; }
      65             :   };
      66             : 
      67             : } // end namespace llvm
      68             : 
      69             : #endif // LLVM_SUPPORT_UNIQUE_LOCK_H