pulsar-client-cpp/lib/UtilAllocator.h

/**
 * Copyright 2016 Yahoo Inc.
 *
 * Licensed 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.
 */

#ifndef LIB_UTILALLOCATOR_H_
#define LIB_UTILALLOCATOR_H_

#include <boost/aligned_storage.hpp>

class HandlerAllocator : private boost::noncopyable {
 public:
    HandlerAllocator()
            : inUse_(false) {
    }

    void* allocate(std::size_t size) {
        if (!inUse_ && size < storage_.size) {
            inUse_ = true;
            return storage_.address();
        } else {
            return ::operator new(size);
        }
    }

    void deallocate(void* pointer) {
        if (pointer == storage_.address()) {
            inUse_ = false;
        } else {
            ::operator delete(pointer);
        }
    }

 private:
    // Storage space used for handler-based custom memory allocation.
    boost::aligned_storage<1024> storage_;
    bool inUse_;
};

template<typename Handler>
class AllocHandler {
 public:
    AllocHandler(HandlerAllocator& a, Handler h)
            : allocator_(a),
              handler_(h) {
    }

    template<typename Arg1>
    void operator()(Arg1 arg1) {
        handler_(arg1);
    }

    template<typename Arg1, typename Arg2>
    void operator()(Arg1 arg1, Arg2 arg2) {
        handler_(arg1, arg2);
    }

    friend void* asio_handler_allocate(std::size_t size, AllocHandler<Handler>* thisHandler) {
        return thisHandler->allocator_.allocate(size);
    }

    friend void asio_handler_deallocate(void* ptr, std::size_t,
                                        AllocHandler<Handler>* thisHandler) {
        thisHandler->allocator_.deallocate(ptr);
    }

 private:
    HandlerAllocator& allocator_;
    Handler handler_;
};

#endif /* LIB_UTILALLOCATOR_H_ */