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 #include <streambuf>
  16
  17 #include "test_macros.h"
  18
  19 template <class CharT>
  20 struct testbuf
  21     : public std::basic_streambuf<CharT>
  22 {
  23     typedef std::basic_string<CharT> string_type;
  24     typedef std::basic_streambuf<CharT> base;
  25 private:
  26     string_type str_;
  27 public:
  28
  29     testbuf() {}
  30     testbuf(const string_type& str)
  31         : str_(str)
  32     {
  33         base::setg(const_cast<CharT*>(str_.data()),
  34                    const_cast<CharT*>(str_.data()),
  35                    const_cast<CharT*>(str_.data()) + str_.size());
  36     }
  37
  38     CharT* eback() const {return base::eback();}
  39     CharT* gptr() const {return base::gptr();}
  40     CharT* egptr() const {return base::egptr();}
  41 };
  42
  43 int main(int, char**)
  44 {
  45     {
  46         testbuf<char> sb(" 123456789");
  47         std::istream is(&sb);
  48         is.get();
  49         is.get();
  50         is.get();
  51         is.unget();
  52         assert(is.good());
  53         assert(is.gcount() == 0);
  54         is.unget();
  55         assert(is.good());
  56         assert(is.gcount() == 0);
  57         is.unget();
  58         assert(is.good());
  59         assert(is.gcount() == 0);
  60         is.unget();
  61         assert(is.bad());
  62         assert(is.gcount() == 0);
  63     }
  64 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
  65     {
  66         testbuf<wchar_t> sb(L" 123456789");
  67         std::wistream is(&sb);
  68         is.get();
  69         is.get();
  70         is.get();
  71         is.unget();
  72         assert(is.good());
  73         assert(is.gcount() == 0);
  74         is.unget();
  75         assert(is.good());
  76         assert(is.gcount() == 0);
  77         is.unget();
  78         assert(is.good());
  79         assert(is.gcount() == 0);
  80         is.unget();
  81         assert(is.bad());
  82         assert(is.gcount() == 0);
  83     }
  84 #endif
  85 #ifndef TEST_HAS_NO_EXCEPTIONS
  86     {
  87         testbuf<char> sb;
  88         std::basic_istream<char> is(&sb);
  89         is.exceptions(std::ios_base::badbit);
  90         bool threw = false;
  91         try {
  92             is.unget();
  93         } catch (std::ios_base::failure&) {
  94             threw = true;
  95         }
  96         assert(threw);
  97         assert( is.bad());
  98         assert(!is.eof());
  99         assert( is.fail());
 100     }
 101 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
 102     {
 103         testbuf<wchar_t> sb;
 104         std::basic_istream<wchar_t> is(&sb);
 105         is.exceptions(std::ios_base::badbit);
 106         bool threw = false;
 107         try {
 108             is.unget();
 109         } catch (std::ios_base::failure&) {
 110             threw = true;
 111         }
 112         assert(threw);
 113         assert( is.bad());
 114         assert(!is.eof());
 115         assert( is.fail());
 116     }
 117 #endif
 118 #endif // TEST_HAS_NO_EXCEPTIONS
 119
 120     return 0;
 121 }