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212 lines
7.3 KiB
C
212 lines
7.3 KiB
C
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// Copyright 2007 The RE2 Authors. All Rights Reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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* A simple mutex wrapper, supporting locks and read-write locks.
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* You should assume the locks are *not* re-entrant.
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*/
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#ifndef RE2_UTIL_MUTEX_H_
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#define RE2_UTIL_MUTEX_H_
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#include <stdlib.h>
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namespace re2 {
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#define HAVE_PTHREAD 1
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#define HAVE_RWLOCK 1
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#if defined(NO_THREADS)
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typedef int MutexType; // to keep a lock-count
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#elif defined(HAVE_PTHREAD) && defined(HAVE_RWLOCK)
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// Needed for pthread_rwlock_*. If it causes problems, you could take it
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// out, but then you'd have to unset HAVE_RWLOCK (at least on linux -- it
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// *does* cause problems for FreeBSD, or MacOSX, but isn't needed
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// for locking there.)
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# ifdef __linux__
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# undef _XOPEN_SOURCE
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# define _XOPEN_SOURCE 500 // may be needed to get the rwlock calls
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# endif
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# include <pthread.h>
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typedef pthread_rwlock_t MutexType;
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#elif defined(HAVE_PTHREAD)
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# include <pthread.h>
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typedef pthread_mutex_t MutexType;
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#elif defined(WIN32)
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# define WIN32_LEAN_AND_MEAN // We only need minimal includes
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# ifdef GMUTEX_TRYLOCK
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// We need Windows NT or later for TryEnterCriticalSection(). If you
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// don't need that functionality, you can remove these _WIN32_WINNT
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// lines, and change TryLock() to assert(0) or something.
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# ifndef _WIN32_WINNT
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# define _WIN32_WINNT 0x0400
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# endif
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# endif
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# include <windows.h>
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typedef CRITICAL_SECTION MutexType;
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#else
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# error Need to implement mutex.h for your architecture, or #define NO_THREADS
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#endif
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class Mutex {
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public:
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// Create a Mutex that is not held by anybody.
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inline Mutex();
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// Destructor
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inline ~Mutex();
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inline void Lock(); // Block if needed until free then acquire exclusively
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inline void Unlock(); // Release a lock acquired via Lock()
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inline bool TryLock(); // If free, Lock() and return true, else return false
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// Note that on systems that don't support read-write locks, these may
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// be implemented as synonyms to Lock() and Unlock(). So you can use
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// these for efficiency, but don't use them anyplace where being able
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// to do shared reads is necessary to avoid deadlock.
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inline void ReaderLock(); // Block until free or shared then acquire a share
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inline void ReaderUnlock(); // Release a read share of this Mutex
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inline void WriterLock() { Lock(); } // Acquire an exclusive lock
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inline void WriterUnlock() { Unlock(); } // Release a lock from WriterLock()
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inline void AssertHeld() { }
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private:
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MutexType mutex_;
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// Catch the error of writing Mutex when intending MutexLock.
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Mutex(Mutex *ignored);
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// Disallow "evil" constructors
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Mutex(const Mutex&);
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void operator=(const Mutex&);
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};
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// Now the implementation of Mutex for various systems
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#if defined(NO_THREADS)
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// When we don't have threads, we can be either reading or writing,
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// but not both. We can have lots of readers at once (in no-threads
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// mode, that's most likely to happen in recursive function calls),
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// but only one writer. We represent this by having mutex_ be -1 when
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// writing and a number > 0 when reading (and 0 when no lock is held).
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//
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// In debug mode, we assert these invariants, while in non-debug mode
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// we do nothing, for efficiency. That's why everything is in an
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// assert.
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#include <assert.h>
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Mutex::Mutex() : mutex_(0) { }
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Mutex::~Mutex() { assert(mutex_ == 0); }
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void Mutex::Lock() { assert(--mutex_ == -1); }
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void Mutex::Unlock() { assert(mutex_++ == -1); }
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bool Mutex::TryLock() { if (mutex_) return false; Lock(); return true; }
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void Mutex::ReaderLock() { assert(++mutex_ > 0); }
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void Mutex::ReaderUnlock() { assert(mutex_-- > 0); }
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#elif defined(HAVE_PTHREAD) && defined(HAVE_RWLOCK)
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#define SAFE_PTHREAD(fncall) do { if ((fncall) != 0) abort(); } while (0)
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Mutex::Mutex() { SAFE_PTHREAD(pthread_rwlock_init(&mutex_, NULL)); }
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Mutex::~Mutex() { SAFE_PTHREAD(pthread_rwlock_destroy(&mutex_)); }
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void Mutex::Lock() { SAFE_PTHREAD(pthread_rwlock_wrlock(&mutex_)); }
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void Mutex::Unlock() { SAFE_PTHREAD(pthread_rwlock_unlock(&mutex_)); }
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bool Mutex::TryLock() { return pthread_rwlock_trywrlock(&mutex_) == 0; }
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void Mutex::ReaderLock() { SAFE_PTHREAD(pthread_rwlock_rdlock(&mutex_)); }
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void Mutex::ReaderUnlock() { SAFE_PTHREAD(pthread_rwlock_unlock(&mutex_)); }
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#undef SAFE_PTHREAD
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#elif defined(HAVE_PTHREAD)
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#define SAFE_PTHREAD(fncall) do { if ((fncall) != 0) abort(); } while (0)
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Mutex::Mutex() { SAFE_PTHREAD(pthread_mutex_init(&mutex_, NULL)); }
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Mutex::~Mutex() { SAFE_PTHREAD(pthread_mutex_destroy(&mutex_)); }
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void Mutex::Lock() { SAFE_PTHREAD(pthread_mutex_lock(&mutex_)); }
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void Mutex::Unlock() { SAFE_PTHREAD(pthread_mutex_unlock(&mutex_)); }
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bool Mutex::TryLock() { return pthread_mutex_trylock(&mutex_) == 0; }
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void Mutex::ReaderLock() { Lock(); } // we don't have read-write locks
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void Mutex::ReaderUnlock() { Unlock(); }
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#undef SAFE_PTHREAD
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#elif defined(WIN32)
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Mutex::Mutex() { InitializeCriticalSection(&mutex_); }
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Mutex::~Mutex() { DeleteCriticalSection(&mutex_); }
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void Mutex::Lock() { EnterCriticalSection(&mutex_); }
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void Mutex::Unlock() { LeaveCriticalSection(&mutex_); }
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bool Mutex::TryLock() { return TryEnterCriticalSection(&mutex_) != 0; }
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void Mutex::ReaderLock() { Lock(); } // we don't have read-write locks
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void Mutex::ReaderUnlock() { Unlock(); }
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#endif
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// --------------------------------------------------------------------------
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// Some helper classes
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// MutexLock(mu) acquires mu when constructed and releases it when destroyed.
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class MutexLock {
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public:
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explicit MutexLock(Mutex *mu) : mu_(mu) { mu_->Lock(); }
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~MutexLock() { mu_->Unlock(); }
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private:
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Mutex * const mu_;
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// Disallow "evil" constructors
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MutexLock(const MutexLock&);
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void operator=(const MutexLock&);
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};
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// ReaderMutexLock and WriterMutexLock do the same, for rwlocks
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class ReaderMutexLock {
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public:
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explicit ReaderMutexLock(Mutex *mu) : mu_(mu) { mu_->ReaderLock(); }
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~ReaderMutexLock() { mu_->ReaderUnlock(); }
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private:
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Mutex * const mu_;
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// Disallow "evil" constructors
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ReaderMutexLock(const ReaderMutexLock&);
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void operator=(const ReaderMutexLock&);
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};
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class WriterMutexLock {
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public:
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explicit WriterMutexLock(Mutex *mu) : mu_(mu) { mu_->WriterLock(); }
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~WriterMutexLock() { mu_->WriterUnlock(); }
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private:
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Mutex * const mu_;
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// Disallow "evil" constructors
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WriterMutexLock(const WriterMutexLock&);
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void operator=(const WriterMutexLock&);
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};
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// Catch bug where variable name is omitted, e.g. MutexLock (&mu);
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#define MutexLock(x) COMPILE_ASSERT(0, mutex_lock_decl_missing_var_name)
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#define ReaderMutexLock(x) COMPILE_ASSERT(0, rmutex_lock_decl_missing_var_name)
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#define WriterMutexLock(x) COMPILE_ASSERT(0, wmutex_lock_decl_missing_var_name)
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// Provide safe way to declare and use global, linker-initialized mutex. Sigh.
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#ifdef HAVE_PTHREAD
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#define GLOBAL_MUTEX(name) \
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static pthread_mutex_t (name) = PTHREAD_MUTEX_INITIALIZER
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#define GLOBAL_MUTEX_LOCK(name) \
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pthread_mutex_lock(&(name))
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#define GLOBAL_MUTEX_UNLOCK(name) \
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pthread_mutex_unlock(&(name))
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#else
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#define GLOBAL_MUTEX(name) \
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static Mutex name
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#define GLOBAL_MUTEX_LOCK(name) \
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name.Lock()
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#define GLOBAL_MUTEX_UNLOCK(name) \
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name.Unlock()
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#endif
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} // namespace re2
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#endif /* #define RE2_UTIL_MUTEX_H_ */
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