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(off_type off, ios_base::seekdir dir);
13
14 #include <istream>
15 #include <cassert>
16
17 int seekoff_called = 0;
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
testbuftestbuf29 testbuf() {}
testbuftestbuf30 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
ebacktestbuf38 CharT* eback() const {return base::eback();}
gptrtestbuf39 CharT* gptr() const {return base::gptr();}
egptrtestbuf40 CharT* egptr() const {return base::egptr();}
41 protected:
seekofftestbuf42 typename base::pos_type seekoff(typename base::off_type off,
43 std::ios_base::seekdir way,
44 std::ios_base::openmode which)
45 {
46 assert(which == std::ios_base::in);
47 ++seekoff_called;
48 return off;
49 }
50 };
51
main()52 int main()
53 {
54 {
55 testbuf<char> sb(" 123456789");
56 std::istream is(&sb);
57 is.seekg(5, std::ios_base::cur);
58 assert(is.good());
59 assert(seekoff_called == 1);
60 is.seekg(-1, std::ios_base::beg);
61 assert(is.fail());
62 assert(seekoff_called == 2);
63 }
64 {
65 testbuf<wchar_t> sb(L" 123456789");
66 std::wistream is(&sb);
67 is.seekg(5, std::ios_base::cur);
68 assert(is.good());
69 assert(seekoff_called == 3);
70 is.seekg(-1, std::ios_base::beg);
71 assert(is.fail());
72 assert(seekoff_called == 4);
73 }
74 }
75