1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 // <istream>
10 
11 // basic_istream<charT,traits>& unget();
12 
13 #include <istream>
14 #include <cassert>
15 
16 #include "test_macros.h"
17 
18 template <class CharT>
19 struct testbuf
20     : public std::basic_streambuf<CharT>
21 {
22     typedef std::basic_string<CharT> string_type;
23     typedef std::basic_streambuf<CharT> base;
24 private:
25     string_type str_;
26 public:
27 
testbuftestbuf28     testbuf() {}
testbuftestbuf29     testbuf(const string_type& str)
30         : str_(str)
31     {
32         base::setg(const_cast<CharT*>(str_.data()),
33                    const_cast<CharT*>(str_.data()),
34                    const_cast<CharT*>(str_.data()) + str_.size());
35     }
36 
ebacktestbuf37     CharT* eback() const {return base::eback();}
gptrtestbuf38     CharT* gptr() const {return base::gptr();}
egptrtestbuf39     CharT* egptr() const {return base::egptr();}
40 };
41 
main(int,char **)42 int main(int, char**)
43 {
44     {
45         testbuf<char> sb(" 123456789");
46         std::istream is(&sb);
47         is.get();
48         is.get();
49         is.get();
50         is.unget();
51         assert(is.good());
52         assert(is.gcount() == 0);
53         is.unget();
54         assert(is.good());
55         assert(is.gcount() == 0);
56         is.unget();
57         assert(is.good());
58         assert(is.gcount() == 0);
59         is.unget();
60         assert(is.bad());
61         assert(is.gcount() == 0);
62     }
63     {
64         testbuf<wchar_t> sb(L" 123456789");
65         std::wistream is(&sb);
66         is.get();
67         is.get();
68         is.get();
69         is.unget();
70         assert(is.good());
71         assert(is.gcount() == 0);
72         is.unget();
73         assert(is.good());
74         assert(is.gcount() == 0);
75         is.unget();
76         assert(is.good());
77         assert(is.gcount() == 0);
78         is.unget();
79         assert(is.bad());
80         assert(is.gcount() == 0);
81     }
82 #ifndef TEST_HAS_NO_EXCEPTIONS
83     {
84         testbuf<char> sb;
85         std::basic_istream<char> is(&sb);
86         is.exceptions(std::ios_base::badbit);
87         bool threw = false;
88         try {
89             is.unget();
90         } catch (std::ios_base::failure&) {
91             threw = true;
92         }
93         assert(threw);
94         assert( is.bad());
95         assert(!is.eof());
96         assert( is.fail());
97     }
98     {
99         testbuf<wchar_t> sb;
100         std::basic_istream<wchar_t> is(&sb);
101         is.exceptions(std::ios_base::badbit);
102         bool threw = false;
103         try {
104             is.unget();
105         } catch (std::ios_base::failure&) {
106             threw = true;
107         }
108         assert(threw);
109         assert( is.bad());
110         assert(!is.eof());
111         assert( is.fail());
112     }
113 #endif
114 
115     return 0;
116 }
117