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      1 //===----------------------------------------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is dual licensed under the MIT and the University of Illinois Open
      6 // Source Licenses. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 // <fstream>
     11 
     12 // template <class charT, class traits = char_traits<charT> >
     13 // class basic_fstream
     14 
     15 // void swap(basic_fstream& rhs);
     16 
     17 #include <fstream>
     18 #include <utility>
     19 #include <cassert>
     20 #include "platform_support.h"
     21 
     22 std::pair<std::string, std::string> get_temp_file_names() {
     23   std::pair<std::string, std::string> names;
     24   names.first = get_temp_file_name();
     25 
     26   // Create the file so the next call to `get_temp_file_name()` doesn't
     27   // return the same file.
     28   std::FILE *fd1 = std::fopen(names.first.c_str(), "w");
     29 
     30   names.second = get_temp_file_name();
     31   assert(names.first != names.second);
     32 
     33   std::fclose(fd1);
     34   std::remove(names.first.c_str());
     35 
     36   return names;
     37 }
     38 
     39 int main()
     40 {
     41     std::pair<std::string, std::string> temp_files = get_temp_file_names();
     42     std::string& temp1 = temp_files.first;
     43     std::string& temp2 = temp_files.second;
     44     assert(temp1 != temp2);
     45     {
     46         std::fstream fs1(temp1.c_str(), std::ios_base::in | std::ios_base::out
     47                                                   | std::ios_base::trunc);
     48         std::fstream fs2(temp2.c_str(), std::ios_base::in | std::ios_base::out
     49                                                   | std::ios_base::trunc);
     50         fs1 << 1 << ' ' << 2;
     51         fs2 << 2 << ' ' << 1;
     52         fs1.seekg(0);
     53         fs1.swap(fs2);
     54         fs1.seekg(0);
     55         int i;
     56         fs1 >> i;
     57         assert(i == 2);
     58         fs1 >> i;
     59         assert(i == 1);
     60         i = 0;
     61         fs2 >> i;
     62         assert(i == 1);
     63         fs2 >> i;
     64         assert(i == 2);
     65     }
     66     std::remove(temp1.c_str());
     67     std::remove(temp2.c_str());
     68     {
     69         std::wfstream fs1(temp1.c_str(), std::ios_base::in | std::ios_base::out
     70                                                    | std::ios_base::trunc);
     71         std::wfstream fs2(temp2.c_str(), std::ios_base::in | std::ios_base::out
     72                                                    | std::ios_base::trunc);
     73         fs1 << 1 << ' ' << 2;
     74         fs2 << 2 << ' ' << 1;
     75         fs1.seekg(0);
     76         fs1.swap(fs2);
     77         fs1.seekg(0);
     78         int i;
     79         fs1 >> i;
     80         assert(i == 2);
     81         fs1 >> i;
     82         assert(i == 1);
     83         i = 0;
     84         fs2 >> i;
     85         assert(i == 1);
     86         fs2 >> i;
     87         assert(i == 2);
     88     }
     89     std::remove(temp1.c_str());
     90     std::remove(temp2.c_str());
     91 }
     92