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 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();} 41 protected: 42 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 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
