boost/detail/basic_pointerbuf.hpp

0001 //-----------------------------------------------------------------------------
0002 // boost detail/templated_streams.hpp header file
0003 // See http://www.boost.org for updates, documentation, and revision history.
0004 //-----------------------------------------------------------------------------
0005 //
0006 // Copyright (c) 2013 John Maddock, Antony Polukhin
0007 //
0008 //
0009 // Distributed under the Boost Software License, Version 1.0. (See
0010 // accompanying file LICENSE_1_0.txt or copy at
0011 // http://www.boost.org/LICENSE_1_0.txt)
0012
0013 #ifndef BOOST_DETAIL_BASIC_POINTERBUF_HPP
0014 #define BOOST_DETAIL_BASIC_POINTERBUF_HPP
0015
0016 // MS compatible compilers support #pragma once
0017 #if defined(_MSC_VER)
0018 # pragma once
0019 #endif
0020
0021 #include "boost/config.hpp"
0022 #include <streambuf>
0023
0024 namespace boost { namespace detail {
0025
0026 //
0027 // class basic_pointerbuf:
0028 // acts as a stream buffer which wraps around a pair of pointers:
0029 //
0030 template <class charT, class BufferT >
0031 class basic_pointerbuf : public BufferT {
0032 protected:
0033    typedef BufferT base_type;
0034    typedef basic_pointerbuf<charT, BufferT> this_type;
0035    typedef typename base_type::int_type int_type;
0036    typedef typename base_type::char_type char_type;
0037    typedef typename base_type::pos_type pos_type;
0038    typedef ::std::streamsize streamsize;
0039    typedef typename base_type::off_type off_type;
0040
0041 public:
0042    basic_pointerbuf() : base_type() { this_type::setbuf(0, 0); }
0043    const charT* getnext() { return this->gptr(); }
0044
0045     using base_type::pptr;
0046     using base_type::pbase;
0047
0048 protected:
0049    // VC mistakenly assumes that `setbuf` and other functions are not referenced.
0050    // Marking those functions with `inline` suppresses the warnings.
0051    // There must be no harm from marking virtual functions as inline: inline virtual
0052    // call can be inlined ONLY when the compiler knows the "exact class".
0053    inline base_type* setbuf(char_type* s, streamsize n) BOOST_OVERRIDE;
0054    inline typename this_type::pos_type seekpos(pos_type sp, ::std::ios_base::openmode which) BOOST_OVERRIDE;
0055    inline typename this_type::pos_type seekoff(off_type off, ::std::ios_base::seekdir way, ::std::ios_base::openmode which) BOOST_OVERRIDE;
0056
0057 private:
0058    basic_pointerbuf& operator=(const basic_pointerbuf&);
0059    basic_pointerbuf(const basic_pointerbuf&);
0060 };
0061
0062 template<class charT, class BufferT>
0063 BufferT*
0064 basic_pointerbuf<charT, BufferT>::setbuf(char_type* s, streamsize n)
0065 {
0066    this->setg(s, s, s + n);
0067    return this;
0068 }
0069
0070 template<class charT, class BufferT>
0071 typename basic_pointerbuf<charT, BufferT>::pos_type
0072 basic_pointerbuf<charT, BufferT>::seekoff(off_type off, ::std::ios_base::seekdir way, ::std::ios_base::openmode which)
0073 {
0074    typedef typename boost::int_t<sizeof(way) * CHAR_BIT>::least cast_type;
0075
0076    if(which & ::std::ios_base::out)
0077       return pos_type(off_type(-1));
0078    std::ptrdiff_t size = this->egptr() - this->eback();
0079    std::ptrdiff_t pos = this->gptr() - this->eback();
0080    charT* g = this->eback();
0081    switch(static_cast<cast_type>(way))
0082    {
0083    case ::std::ios_base::beg:
0084       if((off < 0) || (off > size))
0085          return pos_type(off_type(-1));
0086       else
0087          this->setg(g, g + off, g + size);
0088       break;
0089    case ::std::ios_base::end:
0090       if((off < 0) || (off > size))
0091          return pos_type(off_type(-1));
0092       else
0093          this->setg(g, g + size - off, g + size);
0094       break;
0095    case ::std::ios_base::cur:
0096    {
0097       std::ptrdiff_t newpos = static_cast<std::ptrdiff_t>(pos + off);
0098       if((newpos < 0) || (newpos > size))
0099          return pos_type(off_type(-1));
0100       else
0101          this->setg(g, g + newpos, g + size);
0102       break;
0103    }
0104    default: ;
0105    }
0106 #ifdef BOOST_MSVC
0107 #pragma warning(push)
0108 #pragma warning(disable:4244)
0109 #endif
0110    return static_cast<pos_type>(this->gptr() - this->eback());
0111 #ifdef BOOST_MSVC
0112 #pragma warning(pop)
0113 #endif
0114 }
0115
0116 template<class charT, class BufferT>
0117 typename basic_pointerbuf<charT, BufferT>::pos_type
0118 basic_pointerbuf<charT, BufferT>::seekpos(pos_type sp, ::std::ios_base::openmode which)
0119 {
0120    if(which & ::std::ios_base::out)
0121       return pos_type(off_type(-1));
0122    off_type size = static_cast<off_type>(this->egptr() - this->eback());
0123    charT* g = this->eback();
0124    if(off_type(sp) <= size)
0125    {
0126       this->setg(g, g + off_type(sp), g + size);
0127    }
0128    return pos_type(off_type(-1));
0129 }
0130
0131 }} // namespace boost::detail
0132
0133 #endif // BOOST_DETAIL_BASIC_POINTERBUF_HPP