boost/spirit/home/support/iterators/detail/istream_policy.hpp
// Copyright (c) 2001 Daniel C. Nuffer
// Copyright (c) 2001-2011 Hartmut Kaiser
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#if !defined(BOOST_SPIRIT_ISTREAM_POLICY_JAN_04_2010_0130PM)
#define BOOST_SPIRIT_ISTREAM_POLICY_JAN_04_2010_0130PM
#include <boost/spirit/home/support/iterators/multi_pass_fwd.hpp>
#include <boost/spirit/home/support/iterators/detail/multi_pass.hpp>
namespace boost { namespace spirit { namespace iterator_policies
{
///////////////////////////////////////////////////////////////////////////
// class istream
// Implementation of the InputPolicy used by multi_pass
//
// The istream encapsulates an std::basic_istream
///////////////////////////////////////////////////////////////////////////
struct istream
{
///////////////////////////////////////////////////////////////////////
template <typename T>
class unique // : public detail::default_input_policy
{
private:
typedef typename T::char_type result_type;
public:
typedef typename T::off_type difference_type;
typedef typename T::off_type distance_type;
typedef result_type const* pointer;
typedef result_type const& reference;
typedef result_type value_type;
protected:
unique() {}
explicit unique(T&) {}
void swap(unique&) {}
public:
template <typename MultiPass>
static void destroy(MultiPass&) {}
template <typename MultiPass>
static typename MultiPass::reference get_input(MultiPass& mp)
{
if (!mp.shared()->initialized_)
mp.shared()->read_one();
return mp.shared()->curtok_;
}
template <typename MultiPass>
static void advance_input(MultiPass& mp)
{
// We invalidate the currently cached input character to avoid
// reading more input from the underlying iterator than
// required. Without this we would always read ahead one
// character, even if this character never gets consumed by the
// client.
mp.shared()->peek_one();
}
// test, whether we reached the end of the underlying stream
template <typename MultiPass>
static bool input_at_eof(MultiPass const& mp)
{
return mp.shared()->eof_reached_;
}
template <typename MultiPass>
static bool input_is_valid(MultiPass const& mp, value_type const&)
{
return mp.shared()->initialized_;
}
// no unique data elements
};
///////////////////////////////////////////////////////////////////////
template <typename T>
struct shared
{
private:
typedef typename T::char_type result_type;
public:
explicit shared(T& input)
: input_(input), curtok_(-1)
, initialized_(false), eof_reached_(false)
{
peek_one(); // istreams may be at eof right in the beginning
}
void read_one()
{
if (!(input_ >> curtok_)) {
initialized_ = false;
eof_reached_ = true;
}
else {
initialized_ = true;
}
}
void peek_one()
{
input_.peek(); // try for eof
initialized_ = false;
eof_reached_ = input_.eof();
}
T& input_;
result_type curtok_;
bool initialized_;
bool eof_reached_;
};
};
}}}
#endif