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>& putback(char_type c);
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.putback('a');
50         assert(is.bad());
51         assert(is.gcount() == 0);
52         is.clear();
53         is.putback('2');
54         assert(is.good());
55         assert(is.gcount() == 0);
56         is.putback('1');
57         assert(is.good());
58         assert(is.gcount() == 0);
59         is.putback(' ');
60         assert(is.good());
61         assert(is.gcount() == 0);
62         is.putback(' ');
63         assert(is.bad());
64         assert(is.gcount() == 0);
65     }
66     {
67         testbuf<wchar_t> sb(L" 123456789");
68         std::wistream is(&sb);
69         is.get();
70         is.get();
71         is.get();
72         is.putback(L'a');
73         assert(is.bad());
74         assert(is.gcount() == 0);
75         is.clear();
76         is.putback(L'2');
77         assert(is.good());
78         assert(is.gcount() == 0);
79         is.putback(L'1');
80         assert(is.good());
81         assert(is.gcount() == 0);
82         is.putback(L' ');
83         assert(is.good());
84         assert(is.gcount() == 0);
85         is.putback(L' ');
86         assert(is.bad());
87         assert(is.gcount() == 0);
88     }
89 }
90