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/** |
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* This file is part of the CernVM File System. |
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*/ |
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#ifndef CVMFS_UTIL_MUTEX_H_ |
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#define CVMFS_UTIL_MUTEX_H_ |
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#include <pthread.h> |
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#include "util/single_copy.h" |
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#ifdef CVMFS_NAMESPACE_GUARD |
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namespace CVMFS_NAMESPACE_GUARD { |
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#endif |
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/** |
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* Used to allow for static polymorphism in the RAII template to statically |
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* decide which 'lock' functions to use, if we have more than one possibility. |
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* (I.e. Read/Write locks) |
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* Note: Static Polymorphism - Strategy Pattern |
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* |
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* TODO(jblomer): eventually replace this by C++11 typed enum |
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*/ |
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struct RAII_Polymorphism { |
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enum T { |
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None, |
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ReadLock, |
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WriteLock |
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}; |
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}; |
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/** |
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* Basic template wrapper class for any kind of RAII-like behavior. |
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* The user is supposed to provide a template specialization of Enter() and |
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* Leave(). On creation of the RAII object it will call Enter() respectively |
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* Leave() on destruction. The gold standard example is a LockGard (see below). |
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* |
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* Note: Resource Acquisition Is Initialization (Bjarne Stroustrup) |
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*/ |
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template<typename T, RAII_Polymorphism::T P = RAII_Polymorphism::None> |
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class RAII : SingleCopy { |
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public: |
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inline explicit RAII(T &object) : ref_(object) { Enter(); } |
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inline explicit RAII(T *object) : ref_(*object) { Enter(); } |
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inline ~RAII() { Leave(); } |
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protected: |
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inline void Enter() { ref_.Lock(); } |
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inline void Leave() { ref_.Unlock(); } |
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private: |
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T &ref_; |
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}; |
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/** |
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* This is a simple scoped lock implementation. Every object that provides the |
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* methods Lock() and Unlock() should work with it. Classes that will be used |
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* with this template should therefore simply inherit from Lockable. |
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* |
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* Creating a LockGuard object on the stack will lock the provided object. When |
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* the LockGuard runs out of scope it will automatically release the lock. This |
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* ensures a clean unlock in a lot of situations! |
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* |
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* TODO(jblomer): C++11 replace this by a type alias to RAII |
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*/ |
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template<typename LockableT> |
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class LockGuard : public RAII<LockableT> { |
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public: |
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inline explicit LockGuard(LockableT *object) : RAII<LockableT>(object) { } |
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}; |
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template<> |
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inline void RAII<pthread_mutex_t>::Enter() { |
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pthread_mutex_lock(&ref_); |
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} |
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template<> |
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inline void RAII<pthread_mutex_t>::Leave() { |
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pthread_mutex_unlock(&ref_); |
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} |
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typedef RAII<pthread_mutex_t> MutexLockGuard; |
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template<> |
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inline void RAII<pthread_rwlock_t, RAII_Polymorphism::ReadLock>::Enter() { |
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pthread_rwlock_rdlock(&ref_); |
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} |
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template<> |
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inline void RAII<pthread_rwlock_t, RAII_Polymorphism::ReadLock>::Leave() { |
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pthread_rwlock_unlock(&ref_); |
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} |
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template<> |
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inline void RAII<pthread_rwlock_t, RAII_Polymorphism::WriteLock>::Enter() { |
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pthread_rwlock_wrlock(&ref_); |
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} |
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template<> |
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inline void RAII<pthread_rwlock_t, RAII_Polymorphism::WriteLock>::Leave() { |
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pthread_rwlock_unlock(&ref_); |
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} |
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typedef RAII<pthread_rwlock_t, RAII_Polymorphism::ReadLock> ReadLockGuard; |
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typedef RAII<pthread_rwlock_t, RAII_Polymorphism::WriteLock> WriteLockGuard; |
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#ifdef CVMFS_NAMESPACE_GUARD |
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} // namespace CVMFS_NAMESPACE_GUARD |
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#endif |
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#endif // CVMFS_UTIL_MUTEX_H_ |
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