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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 // int_type peek();
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(" 1\n2345\n6");
45         std::istream is(&sb);
46         assert(is.peek() == ' ');
47         assert(!is.eof());
48         assert(!is.fail());
49         assert(is.gcount() == 0);
50         is.get();
51         assert(is.peek() == '1');
52         assert(!is.eof());
53         assert(!is.fail());
54         assert(is.gcount() == 0);
55     }
56     {
57         testbuf<wchar_t> sb(L" 1\n2345\n6");
58         std::wistream is(&sb);
59         assert(is.peek() == L' ');
60         assert(!is.eof());
61         assert(!is.fail());
62         assert(is.gcount() == 0);
63         is.get();
64         assert(is.peek() == L'1');
65         assert(!is.eof());
66         assert(!is.fail());
67         assert(is.gcount() == 0);
68     }
69 }
70