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 // <istream>
11 
12 // basic_istream<charT,traits>& unget();
13 
14 #include <istream>
15 #include <cassert>
16 
17 template <class CharT>
18 struct testbuf
19     : public std::basic_streambuf<CharT>
20 {
21     typedef std::basic_string<CharT> string_type;
22     typedef std::basic_streambuf<CharT> base;
23 private:
24     string_type str_;
25 public:
26 
testbuftestbuf27     testbuf() {}
testbuftestbuf28     testbuf(const string_type& str)
29         : str_(str)
30     {
31         base::setg(const_cast<CharT*>(str_.data()),
32                    const_cast<CharT*>(str_.data()),
33                    const_cast<CharT*>(str_.data()) + str_.size());
34     }
35 
ebacktestbuf36     CharT* eback() const {return base::eback();}
gptrtestbuf37     CharT* gptr() const {return base::gptr();}
egptrtestbuf38     CharT* egptr() const {return base::egptr();}
39 };
40 
main()41 int main()
42 {
43     {
44         testbuf<char> sb(" 123456789");
45         std::istream is(&sb);
46         is.get();
47         is.get();
48         is.get();
49         is.unget();
50         assert(is.good());
51         assert(is.gcount() == 0);
52         is.unget();
53         assert(is.good());
54         assert(is.gcount() == 0);
55         is.unget();
56         assert(is.good());
57         assert(is.gcount() == 0);
58         is.unget();
59         assert(is.bad());
60         assert(is.gcount() == 0);
61     }
62     {
63         testbuf<wchar_t> sb(L" 123456789");
64         std::wistream is(&sb);
65         is.get();
66         is.get();
67         is.get();
68         is.unget();
69         assert(is.good());
70         assert(is.gcount() == 0);
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.bad());
79         assert(is.gcount() == 0);
80     }
81 }
82