// 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

#include "nv/io/std_stream.hh"
#include <algorithm>
#include <cstring> // TODO: remove, see below

using namespace nv;

std_stream::std_stream( 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_stream::~std_stream()
{
	if ( m_owner )
	{
		delete m_stream;
	}
}

std_stream::int_type std_stream::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
		// TODO: std::copy( egptr() - m_put_back, egptr(), base ); instead?
		std::memmove(base, egptr() - m_put_back, m_put_back);
		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());
}