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// Copyright 2007 The RE2 Authors. All Rights Reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#ifndef UTIL_MUTEX_H_
#define UTIL_MUTEX_H_
/*
* A simple mutex wrapper, supporting locks and read-write locks.
* You should assume the locks are *not* re-entrant.
*/
#ifdef _WIN32
// Requires Windows Vista or Windows Server 2008 at minimum.
#include <windows.h>
#if defined(WINVER) && WINVER >= 0x0600
#define MUTEX_IS_WIN32_SRWLOCK
#endif
#else
#ifndef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 200809L
#endif
#include <unistd.h>
#if defined(_POSIX_READER_WRITER_LOCKS) && _POSIX_READER_WRITER_LOCKS > 0
#define MUTEX_IS_PTHREAD_RWLOCK
#endif
#endif
#if defined(MUTEX_IS_WIN32_SRWLOCK)
typedef SRWLOCK MutexType;
#elif defined(MUTEX_IS_PTHREAD_RWLOCK)
#include <pthread.h>
#include <stdlib.h>
typedef pthread_rwlock_t MutexType;
#else
#include <mutex>
typedef std::mutex MutexType;
#endif
namespace re2 {
class Mutex {
public:
inline Mutex();
inline ~Mutex();
inline void Lock(); // Block if needed until free then acquire exclusively
inline void Unlock(); // Release a lock acquired via Lock()
// Note that on systems that don't support read-write locks, these may
// be implemented as synonyms to Lock() and Unlock(). So you can use
// these for efficiency, but don't use them anyplace where being able
// to do shared reads is necessary to avoid deadlock.
inline void ReaderLock(); // Block until free or shared then acquire a share
inline void ReaderUnlock(); // Release a read share of this Mutex
inline void WriterLock() { Lock(); } // Acquire an exclusive lock
inline void WriterUnlock() { Unlock(); } // Release a lock from WriterLock()
private:
MutexType mutex_;
// Catch the error of writing Mutex when intending MutexLock.
Mutex(Mutex *ignored);
Mutex(const Mutex&) = delete;
Mutex& operator=(const Mutex&) = delete;
};
#if defined(MUTEX_IS_WIN32_SRWLOCK)
Mutex::Mutex() : mutex_(SRWLOCK_INIT) { }
Mutex::~Mutex() { }
void Mutex::Lock() { AcquireSRWLockExclusive(&mutex_); }
void Mutex::Unlock() { ReleaseSRWLockExclusive(&mutex_); }
void Mutex::ReaderLock() { AcquireSRWLockShared(&mutex_); }
void Mutex::ReaderUnlock() { ReleaseSRWLockShared(&mutex_); }
#elif defined(MUTEX_IS_PTHREAD_RWLOCK)
#define SAFE_PTHREAD(fncall) \
do { \
if ((fncall) != 0) abort(); \
} while (0)
Mutex::Mutex() { SAFE_PTHREAD(pthread_rwlock_init(&mutex_, NULL)); }
Mutex::~Mutex() { SAFE_PTHREAD(pthread_rwlock_destroy(&mutex_)); }
void Mutex::Lock() { SAFE_PTHREAD(pthread_rwlock_wrlock(&mutex_)); }
void Mutex::Unlock() { SAFE_PTHREAD(pthread_rwlock_unlock(&mutex_)); }
void Mutex::ReaderLock() { SAFE_PTHREAD(pthread_rwlock_rdlock(&mutex_)); }
void Mutex::ReaderUnlock() { SAFE_PTHREAD(pthread_rwlock_unlock(&mutex_)); }
#undef SAFE_PTHREAD
#else
Mutex::Mutex() { }
Mutex::~Mutex() { }
void Mutex::Lock() { mutex_.lock(); }
void Mutex::Unlock() { mutex_.unlock(); }
void Mutex::ReaderLock() { Lock(); } // C++11 doesn't have std::shared_mutex.
void Mutex::ReaderUnlock() { Unlock(); }
#endif
// --------------------------------------------------------------------------
// Some helper classes
// MutexLock(mu) acquires mu when constructed and releases it when destroyed.
class MutexLock {
public:
explicit MutexLock(Mutex *mu) : mu_(mu) { mu_->Lock(); }
~MutexLock() { mu_->Unlock(); }
private:
Mutex * const mu_;
MutexLock(const MutexLock&) = delete;
MutexLock& operator=(const MutexLock&) = delete;
};
// ReaderMutexLock and WriterMutexLock do the same, for rwlocks
class ReaderMutexLock {
public:
explicit ReaderMutexLock(Mutex *mu) : mu_(mu) { mu_->ReaderLock(); }
~ReaderMutexLock() { mu_->ReaderUnlock(); }
private:
Mutex * const mu_;
ReaderMutexLock(const ReaderMutexLock&) = delete;
ReaderMutexLock& operator=(const ReaderMutexLock&) = delete;
};
class WriterMutexLock {
public:
explicit WriterMutexLock(Mutex *mu) : mu_(mu) { mu_->WriterLock(); }
~WriterMutexLock() { mu_->WriterUnlock(); }
private:
Mutex * const mu_;
WriterMutexLock(const WriterMutexLock&) = delete;
WriterMutexLock& operator=(const WriterMutexLock&) = delete;
};
// Catch bug where variable name is omitted, e.g. MutexLock (&mu);
#define MutexLock(x) static_assert(false, "MutexLock declaration missing variable name")
#define ReaderMutexLock(x) static_assert(false, "ReaderMutexLock declaration missing variable name")
#define WriterMutexLock(x) static_assert(false, "WriterMutexLock declaration missing variable name")
} // namespace re2
#endif // UTIL_MUTEX_H_
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