src/butil/ptr_container.h

// 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.

// Date: Fri Sep  7 12:15:23 CST 2018

#ifndef BUTIL_PTR_CONTAINER_H
#define BUTIL_PTR_CONTAINER_H

namespace butil {

// Manage lifetime of a pointer. The key difference between PtrContainer and
// unique_ptr is that PtrContainer can be copied and the pointer inside is
// deeply copied or constructed on-demand.
template <typename T>
class PtrContainer {
public:
    PtrContainer() : _ptr(NULL) {}

    explicit PtrContainer(T* obj) : _ptr(obj) {}

    ~PtrContainer() {
        delete _ptr;
    }

    PtrContainer(const PtrContainer& rhs)
        : _ptr(rhs._ptr ? new T(*rhs._ptr) : NULL) {}
    
    void operator=(const PtrContainer& rhs) {
        if (this == &rhs) {
            return;
        }

        if (rhs._ptr) {
            if (_ptr) {
                *_ptr = *rhs._ptr;
            } else {
                _ptr = new T(*rhs._ptr);
            }
        } else {
            delete _ptr;
            _ptr = NULL;
        }
    }

    T* get() const { return _ptr; }

    void reset(T* ptr) {
        delete _ptr;
        _ptr = ptr;
    }

    operator void*() const { return _ptr; }

    explicit operator bool() const { return get() != NULL; }

    T& operator*() const { return *get(); }

    T* operator->() const { return get(); }

private:
    T* _ptr;
};

}  // namespace butil

#endif  // BUTIL_PTR_CONTAINER_H