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+// Copyright (c) 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_STUBS_MUTEX_H_
+#define GOOGLE_PROTOBUF_STUBS_MUTEX_H_
+
+#ifdef GOOGLE_PROTOBUF_NO_THREADLOCAL
+#include <pthread.h>
+#endif
+
+#include <google/protobuf/stubs/macros.h>
+
+// ===================================================================
+// emulates google3/base/mutex.h
+namespace google {
+namespace protobuf {
+namespace internal {
+
+// A Mutex is a non-reentrant (aka non-recursive) mutex. At most one thread T
+// may hold a mutex at a given time. If T attempts to Lock() the same Mutex
+// while holding it, T will deadlock.
+class LIBPROTOBUF_EXPORT Mutex {
+ public:
+ // Create a Mutex that is not held by anybody.
+ Mutex();
+
+ // Destructor
+ ~Mutex();
+
+ // Block if necessary until this Mutex is free, then acquire it exclusively.
+ void Lock();
+
+ // Release this Mutex. Caller must hold it exclusively.
+ void Unlock();
+
+ // Crash if this Mutex is not held exclusively by this thread.
+ // May fail to crash when it should; will never crash when it should not.
+ void AssertHeld();
+
+ private:
+ struct Internal;
+ Internal* mInternal;
+
+ GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Mutex);
+};
+
+// Undefine the macros to workaround the conflicts with Google internal
+// MutexLock implementation.
+// TODO(liujisi): Remove the undef once internal macros are removed.
+#undef MutexLock
+#undef ReaderMutexLock
+#undef WriterMutexLock
+#undef MutexLockMaybe
+
+// MutexLock(mu) acquires mu when constructed and releases it when destroyed.
+class LIBPROTOBUF_EXPORT MutexLock {
+ public:
+ explicit MutexLock(Mutex *mu) : mu_(mu) { this->mu_->Lock(); }
+ ~MutexLock() { this->mu_->Unlock(); }
+ private:
+ Mutex *const mu_;
+ GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MutexLock);
+};
+
+// TODO(kenton): Implement these? Hard to implement portably.
+typedef MutexLock ReaderMutexLock;
+typedef MutexLock WriterMutexLock;
+
+// MutexLockMaybe is like MutexLock, but is a no-op when mu is NULL.
+class LIBPROTOBUF_EXPORT MutexLockMaybe {
+ public:
+ explicit MutexLockMaybe(Mutex *mu) :
+ mu_(mu) { if (this->mu_ != NULL) { this->mu_->Lock(); } }
+ ~MutexLockMaybe() { if (this->mu_ != NULL) { this->mu_->Unlock(); } }
+ private:
+ Mutex *const mu_;
+ GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MutexLockMaybe);
+};
+
+#if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL)
+template<typename T>
+class ThreadLocalStorage {
+ public:
+ ThreadLocalStorage() {
+ pthread_key_create(&key_, &ThreadLocalStorage::Delete);
+ }
+ ~ThreadLocalStorage() {
+ pthread_key_delete(key_);
+ }
+ T* Get() {
+ T* result = static_cast<T*>(pthread_getspecific(key_));
+ if (result == NULL) {
+ result = new T();
+ pthread_setspecific(key_, result);
+ }
+ return result;
+ }
+ private:
+ static void Delete(void* value) {
+ delete static_cast<T*>(value);
+ }
+ pthread_key_t key_;
+
+ GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ThreadLocalStorage);
+};
+#endif
+
+} // namespace internal
+
+// We made these internal so that they would show up as such in the docs,
+// but we don't want to stick "internal::" in front of them everywhere.
+using internal::Mutex;
+using internal::MutexLock;
+using internal::ReaderMutexLock;
+using internal::WriterMutexLock;
+using internal::MutexLockMaybe;
+
+
+} // namespace protobuf
+} // namespace google
+
+#endif // GOOGLE_PROTOBUF_STUBS_MUTEX_H_