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      1 /*
      2  * Copyright (C) 2009 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef SCOPED_FD_H_included
     18 #define SCOPED_FD_H_included
     19 
     20 #include <unistd.h>
     21 #include "JNIHelp.h"  // for DISALLOW_COPY_AND_ASSIGN.
     22 
     23 // A smart pointer that closes the given fd on going out of scope.
     24 // Use this when the fd is incidental to the purpose of your function,
     25 // but needs to be cleaned up on exit.
     26 class ScopedFd final {
     27 public:
     28     explicit ScopedFd(int fd) : fd_(fd) {
     29     }
     30     ScopedFd() : ScopedFd(-1) {}
     31 
     32     ~ScopedFd() {
     33       reset();
     34     }
     35 
     36     ScopedFd(ScopedFd&& other) : fd_(other.release()) {}
     37     ScopedFd& operator = (ScopedFd&& s) {
     38         reset(s.release());
     39         return *this;
     40     }
     41 
     42     int get() const {
     43         return fd_;
     44     }
     45 
     46     int release() __attribute__((warn_unused_result)) {
     47         int localFd = fd_;
     48         fd_ = -1;
     49         return localFd;
     50     }
     51 
     52     void reset(int new_fd = -1) {
     53       if (fd_ != -1) {
     54         // Even if close(2) fails with EINTR, the fd will have been closed.
     55         // Using TEMP_FAILURE_RETRY will either lead to EBADF or closing someone else's fd.
     56         // http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
     57         close(fd_);
     58       }
     59       fd_ = new_fd;
     60     }
     61 
     62 private:
     63     int fd_;
     64 
     65     DISALLOW_COPY_AND_ASSIGN(ScopedFd);
     66 };
     67 
     68 #endif  // SCOPED_FD_H_included
     69