Merge "Copy the good comment and warn_unused_result from ScopedFd to unique_fd."

#include <android-base/macros.h>

/* 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() < 0) // invalid descriptor

 *          return error;

 *

 *      // Do something useful

 *

 *      return 0; // descriptor is closed here

 */

// 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 {

  }

  void reset(int new_value) {

    if (value_ >= 0)

    if (value_ != -1) {

      // 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(value_);

    }

    value_ = new_value;

  }

  int get() const { return value_; }

  int release() {

  int release() __attribute__((warn_unused_result)) {

    int ret = value_;

    value_ = -1;

    return ret;