libcxx/test/std/input.output/iostream.format/input.streams/istream.unformatted/seekg_off.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(off_type off, ios_base::seekdir dir);
  12
  13 #include <istream>
  14 #include <cassert>
  15 #include <streambuf>
  16
  17 #include "test_macros.h"
  18
  19 int seekoff_called = 0;
  20
  21 template <class CharT>
  22 struct testbuf
  23     : public std::basic_streambuf<CharT>
  24 {
  25     typedef std::basic_string<CharT> string_type;
  26     typedef std::basic_streambuf<CharT> base;
  27 private:
  28     string_type str_;
  29 public:
  30
  31     testbuf() {}
  32     testbuf(const string_type& str)
  33         : str_(str)
  34     {
  35         base::setg(const_cast<CharT*>(str_.data()),
  36                    const_cast<CharT*>(str_.data()),
  37                    const_cast<CharT*>(str_.data()) + str_.size());
  38     }
  39
  40     CharT* eback() const {return base::eback();}
  41     CharT* gptr() const {return base::gptr();}
  42     CharT* egptr() const {return base::egptr();}
  43 protected:
  44     typename base::pos_type seekoff(typename base::off_type off,
  45                                     std::ios_base::seekdir,
  46                                     std::ios_base::openmode which)
  47     {
  48         assert(which == std::ios_base::in);
  49         ++seekoff_called;
  50         return off;
  51     }
  52 };
  53
  54 int main(int, char**)
  55 {
  56     {
  57         testbuf<char> sb(" 123456789");
  58         std::istream is(&sb);
  59         is.seekg(5, std::ios_base::cur);
  60         assert(is.good());
  61         assert(seekoff_called == 1);
  62         is.seekg(-1, std::ios_base::beg);
  63         assert(is.fail());
  64         assert(seekoff_called == 2);
  65     }
  66 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
  67     {
  68         testbuf<wchar_t> sb(L" 123456789");
  69         std::wistream is(&sb);
  70         is.seekg(5, std::ios_base::cur);
  71         assert(is.good());
  72         assert(seekoff_called == 3);
  73         is.seekg(-1, std::ios_base::beg);
  74         assert(is.fail());
  75         assert(seekoff_called == 4);
  76     }
  77 #endif
  78     {
  79         testbuf<char> sb(" 123456789");
  80         std::istream is(&sb);
  81         is.setstate(std::ios_base::eofbit);
  82         assert(is.eof());
  83         is.seekg(5, std::ios_base::beg);
  84         assert(is.good());
  85         assert(!is.eof());
  86     }
  87
  88   return 0;
  89 }