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//===- Support/UniqueLock.h - Acquire/Release Mutex In Scope ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file 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.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_UNIQUE_LOCK_H
#define LLVM_SUPPORT_UNIQUE_LOCK_H
#include <cassert>
namespace llvm {
/// A pared-down imitation of std::unique_lock from C++11. Contrary to the
/// name, it's really more of a wrapper for a lock. It may or may not have
/// an associated mutex, which is guaranteed to be locked upon creation
/// and unlocked after destruction. unique_lock can also unlock the mutex
/// and re-lock it freely during its lifetime.
/// Guard a section of code with a mutex.
template<typename MutexT>
class unique_lock {
MutexT *M = nullptr;
bool locked = false;
public:
unique_lock() = default;
explicit unique_lock(MutexT &m) : M(&m), locked(true) { M->lock(); }
unique_lock(const unique_lock &) = delete;
unique_lock &operator=(const unique_lock &) = delete;
void operator=(unique_lock &&o) {
if (owns_lock())
M->unlock();
M = o.M;
locked = o.locked;
o.M = nullptr;
o.locked = false;
}
~unique_lock() { if (owns_lock()) M->unlock(); }
void lock() {
assert(!locked && "mutex already locked!");
assert(M && "no associated mutex!");
M->lock();
locked = true;
}
void unlock() {
assert(locked && "unlocking a mutex that isn't locked!");
assert(M && "no associated mutex!");
M->unlock();
locked = false;
}
bool owns_lock() { return locked; }
};
} // end namespace llvm
#endif // LLVM_SUPPORT_UNIQUE_LOCK_H
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