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Diffstat (limited to 'cpp/src/qpid/asyncStore/jrnl2/AtomicCounter.h')
-rw-r--r-- | cpp/src/qpid/asyncStore/jrnl2/AtomicCounter.h | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/cpp/src/qpid/asyncStore/jrnl2/AtomicCounter.h b/cpp/src/qpid/asyncStore/jrnl2/AtomicCounter.h new file mode 100644 index 0000000000..b13caa5462 --- /dev/null +++ b/cpp/src/qpid/asyncStore/jrnl2/AtomicCounter.h @@ -0,0 +1,77 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +/** + * \file AtomicCounter.h + */ + +#ifndef qpid_asyncStore_jrnl2_AtomicCounter_h_ +#define qpid_asyncStore_jrnl2_AtomicCounter_h_ + +#include "ScopedLock.h" + +namespace qpid { +namespace asyncStore { +namespace jrnl2 { + +/** + * \brief Template integral atomic counter class which provides a next() operation to increment then return the + * updated count of integral type T. This operation is performed under a thread lock. + */ +template <class T> class AtomicCounter +{ +public: + /** + * \brief Constructor with an option to set an inital value for the counter. + */ + AtomicCounter(T initialValue = T(0)) : + m_cnt(initialValue) + {} + + /** + * \brief Destructor + */ + virtual ~AtomicCounter() + {} + + /** + * \brief Increment, then return new value of the internal counter. This is thread-safe and takes a lock + * in order to perform the increment. + * + * \note This is a non-zero counter. By default, the counter starts with the value 0, and consequently the + * first call to next() will return 1. Upon overflow, the counter will be incremented twice so as to avoid + * returning the value 0. + */ + virtual T next() + { + // --- START OF CRITICAL SECTION --- + ScopedLock l(m_mutex); + while (!++m_cnt) ; // Cannot return 0x0 if m_cnt should overflow + return m_cnt; + } // --- END OF CRITICAL SECTION --- + +protected: + T m_cnt; ///< Internal count value + ScopedMutex m_mutex; ///< Internal lock used to increment the counter + +}; + +}}} // namespace qpid::asyncStore::jrnl2 + +#endif // qpid_asyncStore_jrnl2_AtomicCounter_h_ |