// 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: Mon. Nov 7 14:47:36 CST 2011

#ifndef BUTIL_FD_GUARD_H

#define BUTIL_FD_GUARD_H

#include <unistd.h>                                  // close()

namespace butil {

// RAII file descriptor.

//

// Example:

//    fd_guard fd1(open(...));

//    if (fd1 < 0) {

//        printf("Fail to open\n");

//        return -1;

//    }

//    if (another-error-happened) {

//        printf("Fail to do sth\n");

//        return -1;   // *** closing fd1 automatically ***

//    }

class fd_guard {

public:

    fd_guard() : _fd(-1) {}

    explicit fd_guard(int fd) : _fd(fd) {}

    ~fd_guard() {

        if (_fd >= 0) {

            ::close(_fd);

            _fd = -1;

        }

    }

    // Close current fd and replace with another fd

    void reset(int fd) {

        if (_fd >= 0) {

            ::close(_fd);

            _fd = -1;

        }

        _fd = fd;

    }

    // Set internal fd to -1 and return the value before set.

    int release() {

        const int prev_fd = _fd;

        _fd = -1;

        return prev_fd;

    }

    operator int() const { return _fd; }

private:

    // Copying this makes no sense.

    fd_guard(const fd_guard&);

    void operator=(const fd_guard&);

    int _fd;

};

}  // namespace butil

#endif  // BUTIL_FD_GUARD_H