source: trunk/src/io/std_stream.cc @ 138

// Copyright (C) 2012-2013 ChaosForge / Kornel Kisielewicz
// http://chaosforge.org/
//
// This file is part of NV Libraries.
// For conditions of distribution and use, see copyright notice in nv.hh
//
// TODO: support for write operations, see http://www.mr-edd.co.uk/blog/beginners_guide_streambuf

#include "nv/io/std_stream.hh"
#include <algorithm>

using namespace nv;

std_streambuf::std_streambuf( stream* source, bool owner /*= false*/, std::size_t bsize /*= 256*/, std::size_t put_back /*= 8 */ )
        : m_stream( source )
        , m_owner( owner )
        , m_put_back( std::max( put_back, std::size_t( 1 ) ) )
        , m_buffer( std::max(bsize, put_back) + put_back )
{
        char *end = &m_buffer.front() + m_buffer.size();
        setg( end, end, end );
}

std_streambuf::~std_streambuf()
{
        if ( m_owner )
        {
                delete m_stream;
        }
}

std_streambuf::int_type std_streambuf::underflow()
{
        if (gptr() < egptr())
        {
                // buffer not exhausted
                return traits_type::to_int_type(*gptr());
        }

        char *base = &m_buffer.front();
        char *start = base;

        if (eback() == base) // true when this isn't the first fill
        {
                // Make arrangements for putback characters
                std::copy( egptr() - m_put_back, egptr(), base ); 
                start += m_put_back;
        }

        // start is now the start of the buffer, proper.
        size_t n = m_stream->read( start, 1, m_buffer.size() - (start - base) );
        if (n == 0)
        {
                return traits_type::eof();
        }

        // Set buffer pointers
        setg(base, start, start + n);

        return traits_type::to_int_type(*gptr());
}