libcxx/test/std/input.output/file.streams/fstreams/filebuf.virtuals/pbackfail.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // <fstream>
  10
  11 // int_type pbackfail(int_type c = traits::eof());
  12
  13 // FILE_DEPENDENCIES: underflow.dat
  14
  15 #include <fstream>
  16 #include <cassert>
  17
  18 #include "test_macros.h"
  19
  20 template <class CharT>
  21 struct test_buf
  22     : public std::basic_filebuf<CharT>
  23 {
  24     typedef std::basic_filebuf<CharT>  base;
  25     typedef typename base::char_type   char_type;
  26     typedef typename base::int_type    int_type;
  27     typedef typename base::traits_type traits_type;
  28
  29     char_type* eback() const {return base::eback();}
  30     char_type* gptr()  const {return base::gptr();}
  31     char_type* egptr() const {return base::egptr();}
  32     void gbump(int n) {base::gbump(n);}
  33
  34     virtual int_type pbackfail(int_type c = traits_type::eof()) {return base::pbackfail(c);}
  35 };
  36
  37 int main(int, char**)
  38 {
  39     {
  40         test_buf<char> f;
  41         assert(f.open("underflow.dat", std::ios_base::in) != 0);
  42         assert(f.is_open());
  43         assert(f.sbumpc() == '1');
  44         assert(f.sgetc() == '2');
  45         typename test_buf<char>::int_type pbackResult = f.pbackfail('a');
  46         LIBCPP_ASSERT(pbackResult == -1);
  47         if (pbackResult != -1) {
  48             assert(f.sbumpc() == 'a');
  49             assert(f.sgetc() == '2');
  50         }
  51     }
  52     {
  53         test_buf<char> f;
  54         assert(f.open("underflow.dat", std::ios_base::in | std::ios_base::out) != 0);
  55         assert(f.is_open());
  56         assert(f.sbumpc() == '1');
  57         assert(f.sgetc() == '2');
  58         typename test_buf<char>::int_type pbackResult = f.pbackfail('a');
  59         LIBCPP_ASSERT(pbackResult == 'a');
  60         if (pbackResult != -1) {
  61             assert(f.sbumpc() == 'a');
  62             assert(f.sgetc() == '2');
  63         }
  64     }
  65
  66   return 0;
  67 }