libcxx/test/std/input.output/iostream.format/output.streams/ostream.seeks/seekp2.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 // <ostream>
  10
  11 // template <class charT, class traits = char_traits<charT> >
  12 //   class basic_ostream;
  13
  14 // basic_ostream<charT,traits>& seekp(off_type off, ios_base::seekdir dir);
  15
  16 #include <ostream>
  17 #include <cassert>
  18
  19 #include "test_macros.h"
  20
  21 int seekoff_called = 0;
  22
  23 template <class CharT>
  24 struct testbuf
  25     : public std::basic_streambuf<CharT>
  26 {
  27     typedef std::basic_streambuf<CharT> base;
  28     testbuf() {}
  29
  30 protected:
  31
  32     typename base::pos_type
  33     seekoff(typename base::off_type off, std::ios_base::seekdir way,
  34                                          std::ios_base::openmode which)
  35     {
  36         ++seekoff_called;
  37         assert(way == std::ios_base::beg);
  38         assert(which == std::ios_base::out);
  39         return off;
  40     }
  41 };
  42
  43 int main(int, char**)
  44 {
  45     {
  46         seekoff_called = 0;
  47         std::ostream os((std::streambuf*)0);
  48         assert(&os.seekp(5, std::ios_base::beg) == &os);
  49         assert(seekoff_called == 0);
  50     }
  51     {
  52         seekoff_called = 0;
  53         testbuf<char> sb;
  54         std::ostream os(&sb);
  55         assert(&os.seekp(10, std::ios_base::beg) == &os);
  56         assert(seekoff_called == 1);
  57         assert(os.good());
  58         assert(&os.seekp(-1, std::ios_base::beg) == &os);
  59         assert(seekoff_called == 2);
  60         assert(os.fail());
  61     }
  62     { // See https://llvm.org/PR21361
  63         seekoff_called = 0;
  64         testbuf<char> sb;
  65         std::ostream os(&sb);
  66         os.setstate(std::ios_base::eofbit);
  67         assert(&os.seekp(10, std::ios_base::beg) == &os);
  68         assert(seekoff_called == 1);
  69         assert(os.rdstate() == std::ios_base::eofbit);
  70     }
  71
  72   return 0;
  73 }