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.
46 namespace android {
47 namespace base {
48
49 struct DefaultCloser {
CloseDefaultCloser50 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
59 template <typename Closer>
60 class unique_fd_impl final {
61 public:
unique_fd_impl()62 unique_fd_impl() : value_(-1) {}
63
unique_fd_impl(int value)64 explicit unique_fd_impl(int value) : value_(value) {}
~unique_fd_impl()65 ~unique_fd_impl() { reset(); }
66
unique_fd_impl(unique_fd_impl && other)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
get()80 int get() const { return value_; }
81 operator int() const { return get(); }
82
release()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
96 using unique_fd = unique_fd_impl<DefaultCloser>;
97
98 #if !defined(_WIN32)
99
100 // Inline functions, so that they can be used header-only.
Pipe(unique_fd * read,unique_fd * write)101 inline 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
Socketpair(int domain,int type,int protocol,unique_fd * left,unique_fd * right)125 inline 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
Socketpair(int type,unique_fd * left,unique_fd * right)135 inline 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
144 template <typename T>
145 int 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