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>& seekg(pos_type pos);
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 protected:
seekpostestbuf40     typename base::pos_type seekpos(typename base::pos_type sp,
41                                     std::ios_base::openmode which)
42     {
43         assert(which == std::ios_base::in);
44         return sp;
45     }
46 };
47 
main()48 int main()
49 {
50     {
51         testbuf<char> sb(" 123456789");
52         std::istream is(&sb);
53         is.seekg(5);
54         assert(is.good());
55         is.seekg(-1);
56         assert(is.fail());
57     }
58     {
59         testbuf<wchar_t> sb(L" 123456789");
60         std::wistream is(&sb);
61         is.seekg(5);
62         assert(is.good());
63         is.seekg(-1);
64         assert(is.fail());
65     }
66 }
67