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

   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
  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
  28     testbuf() {}
  29     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
  37     CharT* eback() const {return base::eback();}
  38     CharT* gptr() const {return base::gptr();}
  39     CharT* egptr() const {return base::egptr();}
  40 protected:
  41     typename base::pos_type seekpos(typename base::pos_type sp,
  42                                     std::ios_base::openmode which)
  43     {
  44         assert(which == std::ios_base::in);
  45         return sp;
  46     }
  47 };
  48
  49 int main(int, char**)
  50 {
  51     {
  52         testbuf<char> sb(" 123456789");
  53         std::istream is(&sb);
  54         is.seekg(5);
  55         assert(is.good());
  56         is.seekg(-1);
  57         assert(is.fail());
  58     }
  59 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
  60     {
  61         testbuf<wchar_t> sb(L" 123456789");
  62         std::wistream is(&sb);
  63         is.seekg(5);
  64         assert(is.good());
  65         is.seekg(-1);
  66         assert(is.fail());
  67     }
  68 #endif
  69     {
  70         testbuf<char> sb(" 123456789");
  71         std::istream is(&sb);
  72         is.setstate(std::ios_base::eofbit);
  73         assert(is.eof());
  74         is.seekg(5);
  75         assert(is.good());
  76         assert(!is.eof());
  77     }
  78
  79   return 0;
  80 }