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include/google/protobuf/stubs/mutex.h

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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);
+};
+
+// 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_