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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed 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.
*/
#ifndef ANDROID_BASE_UNIQUE_FD_H
#define ANDROID_BASE_UNIQUE_FD_H
#include <unistd.h>
// DO NOT INCLUDE OTHER LIBBASE HEADERS!
// This file gets used in libbinder, and libbinder is used everywhere.
// Including other headers from libbase frequently results in inclusion of
// android-base/macros.h, which causes macro collisions.
// Container for a file descriptor that automatically closes the descriptor as
// it goes out of scope.
//
// unique_fd ufd(open("/some/path", "r"));
// if (ufd.get() == -1) return error;
//
// // Do something useful, possibly including 'return'.
//
// return 0; // Descriptor is closed for you.
//
// unique_fd is also known as ScopedFd/ScopedFD/scoped_fd; mentioned here to help
// you find this class if you're searching for one of those names.
namespace android {
namespace base {
struct DefaultCloser {
static void Close(int fd) {
// Even if close(2) fails with EINTR, the fd will have been closed.
// Using TEMP_FAILURE_RETRY will either lead to EBADF or closing someone
// else's fd.
// http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
::close(fd);
}
};
template <typename Closer>
class unique_fd_impl final {
public:
unique_fd_impl() : value_(-1) {}
explicit unique_fd_impl(int value) : value_(value) {}
~unique_fd_impl() { reset(); }
unique_fd_impl(unique_fd_impl&& other) : value_(other.release()) {}
unique_fd_impl& operator=(unique_fd_impl&& s) {
reset(s.release());
return *this;
}
void reset(int new_value = -1) {
if (value_ != -1) {
Closer::Close(value_);
}
value_ = new_value;
}
int get() const { return value_; }
operator int() const { return get(); }
int release() __attribute__((warn_unused_result)) {
int ret = value_;
value_ = -1;
return ret;
}
private:
int value_;
unique_fd_impl(const unique_fd_impl&);
void operator=(const unique_fd_impl&);
};
using unique_fd = unique_fd_impl<DefaultCloser>;
} // namespace base
} // namespace android
template <typename T>
int close(const android::base::unique_fd_impl<T>&)
#if defined(__clang__)
__attribute__((__unavailable__(
#else
__attribute__((__error__(
#endif
"close called on unique_fd"
)));
#endif // ANDROID_BASE_UNIQUE_FD_H
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