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>& seekg(pos_type pos);
12
13#include <istream>
14#include <cassert>
15#include <streambuf>
16
17#include "test_macros.h"
18
19template <class CharT>
20struct testbuf
21 : public std::basic_streambuf<CharT>
22{
23 typedef std::basic_string<CharT> string_type;
24 typedef std::basic_streambuf<CharT> base;
25private:
26 string_type str_;
27public:
28
29 testbuf() {}
30 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
38 CharT* eback() const {return base::eback();}
39 CharT* gptr() const {return base::gptr();}
40 CharT* egptr() const {return base::egptr();}
41protected:
42 typename base::pos_type seekpos(typename base::pos_type sp,
43 std::ios_base::openmode which)
44 {
45 assert(which == std::ios_base::in);
46 return sp;
47 }
48};
49
50int main(int, char**)
51{
52 {
53 testbuf<char> sb(" 123456789");
54 std::istream is(&sb);
55 is.seekg(5);
56 assert(is.good());
57 is.seekg(-1);
58 assert(is.fail());
59 }
60#ifndef TEST_HAS_NO_WIDE_CHARACTERS
61 {
62 testbuf<wchar_t> sb(L" 123456789");
63 std::wistream is(&sb);
64 is.seekg(5);
65 assert(is.good());
66 is.seekg(-1);
67 assert(is.fail());
68 }
69#endif
70 {
71 testbuf<char> sb(" 123456789");
72 std::istream is(&sb);
73 is.setstate(std::ios_base::eofbit);
74 assert(is.eof());
75 is.seekg(5);
76 assert(is.good());
77 assert(!is.eof());
78 }
79
80 return 0;
81}
82

source code of libcxx/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg.pass.cpp