libcxx/test/std/input.output/iostream.format/input.streams/istream.unformatted/unget.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 // <istream>
  10
  11 // basic_istream<charT,traits>& unget();
  12
  13 #include <istream>
  14 #include <cassert>
  15
  16 #include "test_macros.h"
  17
  18 template <class CharT>
  19 struct testbuf
  20     : public std::basic_streambuf<CharT>
  21 {
  22     typedef std::basic_string<CharT> string_type;
  23     typedef std::basic_streambuf<CharT> base;
  24 private:
  25     string_type str_;
  26 public:
  27
  28     testbuf() {}
  29     testbuf(const string_type& str)
  30         : str_(str)
  31     {
  32         base::setg(const_cast<CharT*>(str_.data()),
  33                    const_cast<CharT*>(str_.data()),
  34                    const_cast<CharT*>(str_.data()) + str_.size());
  35     }
  36
  37     CharT* eback() const {return base::eback();}
  38     CharT* gptr() const {return base::gptr();}
  39     CharT* egptr() const {return base::egptr();}
  40 };
  41
  42 int main(int, char**)
  43 {
  44     {
  45         testbuf<char> sb(" 123456789");
  46         std::istream is(&sb);
  47         is.get();
  48         is.get();
  49         is.get();
  50         is.unget();
  51         assert(is.good());
  52         assert(is.gcount() == 0);
  53         is.unget();
  54         assert(is.good());
  55         assert(is.gcount() == 0);
  56         is.unget();
  57         assert(is.good());
  58         assert(is.gcount() == 0);
  59         is.unget();
  60         assert(is.bad());
  61         assert(is.gcount() == 0);
  62     }
  63 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
  64     {
  65         testbuf<wchar_t> sb(L" 123456789");
  66         std::wistream is(&sb);
  67         is.get();
  68         is.get();
  69         is.get();
  70         is.unget();
  71         assert(is.good());
  72         assert(is.gcount() == 0);
  73         is.unget();
  74         assert(is.good());
  75         assert(is.gcount() == 0);
  76         is.unget();
  77         assert(is.good());
  78         assert(is.gcount() == 0);
  79         is.unget();
  80         assert(is.bad());
  81         assert(is.gcount() == 0);
  82     }
  83 #endif
  84 #ifndef TEST_HAS_NO_EXCEPTIONS
  85     {
  86         testbuf<char> sb;
  87         std::basic_istream<char> is(&sb);
  88         is.exceptions(std::ios_base::badbit);
  89         bool threw = false;
  90         try {
  91             is.unget();
  92         } catch (std::ios_base::failure&) {
  93             threw = true;
  94         }
  95         assert(threw);
  96         assert( is.bad());
  97         assert(!is.eof());
  98         assert( is.fail());
  99     }
 100 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
 101     {
 102         testbuf<wchar_t> sb;
 103         std::basic_istream<wchar_t> is(&sb);
 104         is.exceptions(std::ios_base::badbit);
 105         bool threw = false;
 106         try {
 107             is.unget();
 108         } catch (std::ios_base::failure&) {
 109             threw = true;
 110         }
 111         assert(threw);
 112         assert( is.bad());
 113         assert(!is.eof());
 114         assert( is.fail());
 115     }
 116 #endif
 117 #endif // TEST_HAS_NO_EXCEPTIONS
 118
 119     return 0;
 120 }