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 #include <streambuf>
  16
  17 #include "test_macros.h"
  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 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
  50 int 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 }