test/std/input.output/file.streams/fstreams/fstream.assign/member_swap.pass.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// <fstream>

// template <class charT, class traits = char_traits<charT> >
// class basic_fstream

// void swap(basic_fstream& rhs);

#include <fstream>
#include <utility>
#include <cassert>
#include "test_macros.h"
#include "platform_support.h"

std::pair<std::string, std::string> get_temp_file_names() {
  std::pair<std::string, std::string> names;
  names.first = get_temp_file_name();

  // Create the file so the next call to `get_temp_file_name()` doesn't
  // return the same file.
  std::FILE *fd1 = std::fopen(names.first.c_str(), "w");

  names.second = get_temp_file_name();
  assert(names.first != names.second);

  std::fclose(fd1);
  std::remove(names.first.c_str());

  return names;
}

int main(int, char**)
{
    std::pair<std::string, std::string> temp_files = get_temp_file_names();
    std::string& temp1 = temp_files.first;
    std::string& temp2 = temp_files.second;
    assert(temp1 != temp2);
    {
        std::fstream fs1(temp1.c_str(), std::ios_base::in | std::ios_base::out
                                                  | std::ios_base::trunc);
        std::fstream fs2(temp2.c_str(), std::ios_base::in | std::ios_base::out
                                                  | std::ios_base::trunc);
        fs1 << 1 << ' ' << 2;
        fs2 << 2 << ' ' << 1;
        fs1.seekg(0);
        fs1.swap(fs2);
        fs1.seekg(0);
        int i;
        fs1 >> i;
        assert(i == 2);
        fs1 >> i;
        assert(i == 1);
        i = 0;
        fs2 >> i;
        assert(i == 1);
        fs2 >> i;
        assert(i == 2);
    }
    std::remove(temp1.c_str());
    std::remove(temp2.c_str());
    {
        std::wfstream fs1(temp1.c_str(), std::ios_base::in | std::ios_base::out
                                                   | std::ios_base::trunc);
        std::wfstream fs2(temp2.c_str(), std::ios_base::in | std::ios_base::out
                                                   | std::ios_base::trunc);
        fs1 << 1 << ' ' << 2;
        fs2 << 2 << ' ' << 1;
        fs1.seekg(0);
        fs1.swap(fs2);
        fs1.seekg(0);
        int i;
        fs1 >> i;
        assert(i == 2);
        fs1 >> i;
        assert(i == 1);
        i = 0;
        fs2 >> i;
        assert(i == 1);
        fs2 >> i;
        assert(i == 2);
    }
    std::remove(temp1.c_str());
    std::remove(temp2.c_str());

  return 0;
}