1/*
2 * Copyright (C) 2015 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 ANDROID_BASE_UNIQUE_FD_H
18#define ANDROID_BASE_UNIQUE_FD_H
19
20#include <fcntl.h>
21
22#if !defined(_WIN32)
23#include <sys/socket.h>
24#endif
25
26#include <sys/types.h>
27#include <unistd.h>
28
29// DO NOT INCLUDE OTHER LIBBASE HEADERS!
30// This file gets used in libbinder, and libbinder is used everywhere.
31// Including other headers from libbase frequently results in inclusion of
32// android-base/macros.h, which causes macro collisions.
33
34// Container for a file descriptor that automatically closes the descriptor as
35// it goes out of scope.
36//
37//      unique_fd ufd(open("/some/path", "r"));
38//      if (ufd.get() == -1) return error;
39//
40//      // Do something useful, possibly including 'return'.
41//
42//      return 0; // Descriptor is closed for you.
43//
44// unique_fd is also known as ScopedFd/ScopedFD/scoped_fd; mentioned here to help
45// you find this class if you're searching for one of those names.
46namespace android {
47namespace base {
48
49struct DefaultCloser {
50  static void Close(int fd) {
51    // Even if close(2) fails with EINTR, the fd will have been closed.
52    // Using TEMP_FAILURE_RETRY will either lead to EBADF or closing someone
53    // else's fd.
54    // http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
55    ::close(fd);
56  }
57};
58
59template <typename Closer>
60class unique_fd_impl final {
61 public:
62  unique_fd_impl() : value_(-1) {}
63
64  explicit unique_fd_impl(int value) : value_(value) {}
65  ~unique_fd_impl() { reset(); }
66
67  unique_fd_impl(unique_fd_impl&& other) : value_(other.release()) {}
68  unique_fd_impl& operator=(unique_fd_impl&& s) {
69    reset(s.release());
70    return *this;
71  }
72
73  void reset(int new_value = -1) {
74    if (value_ != -1) {
75      Closer::Close(value_);
76    }
77    value_ = new_value;
78  }
79
80  int get() const { return value_; }
81  operator int() const { return get(); }
82
83  int release() __attribute__((warn_unused_result)) {
84    int ret = value_;
85    value_ = -1;
86    return ret;
87  }
88
89 private:
90  int value_;
91
92  unique_fd_impl(const unique_fd_impl&);
93  void operator=(const unique_fd_impl&);
94};
95
96using unique_fd = unique_fd_impl<DefaultCloser>;
97
98#if !defined(_WIN32)
99
100// Inline functions, so that they can be used header-only.
101inline bool Pipe(unique_fd* read, unique_fd* write) {
102  int pipefd[2];
103
104#if defined(__linux__)
105  if (pipe2(pipefd, O_CLOEXEC) != 0) {
106    return false;
107  }
108#else  // defined(__APPLE__)
109  if (pipe(pipefd) != 0) {
110    return false;
111  }
112
113  if (fcntl(pipefd[0], F_SETFD, FD_CLOEXEC) != 0 || fcntl(pipefd[1], F_SETFD, FD_CLOEXEC) != 0) {
114    close(pipefd[0]);
115    close(pipefd[1]);
116    return false;
117  }
118#endif
119
120  read->reset(pipefd[0]);
121  write->reset(pipefd[1]);
122  return true;
123}
124
125inline bool Socketpair(int domain, int type, int protocol, unique_fd* left, unique_fd* right) {
126  int sockfd[2];
127  if (socketpair(domain, type, protocol, sockfd) != 0) {
128    return false;
129  }
130  left->reset(sockfd[0]);
131  right->reset(sockfd[1]);
132  return true;
133}
134
135inline bool Socketpair(int type, unique_fd* left, unique_fd* right) {
136  return Socketpair(AF_UNIX, type, 0, left, right);
137}
138
139#endif  // !defined(_WIN32)
140
141}  // namespace base
142}  // namespace android
143
144template <typename T>
145int close(const android::base::unique_fd_impl<T>&)
146#if defined(__clang__)
147  __attribute__((__unavailable__(
148#else
149  __attribute__((__error__(
150#endif
151    "close called on unique_fd"
152  )));
153
154#endif  // ANDROID_BASE_UNIQUE_FD_H
155