/usr/include/boost/range/adaptor/strided.hpp is in libboost1.49-dev 1.49.0-3.2.
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//
// Copyright Neil Groves 2007. Use, modification and
// distribution is subject to 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)
//
//
// For more information, see http://www.boost.org/libs/range/
//
#ifndef BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED
#define BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED
#include <boost/range/adaptor/argument_fwd.hpp>
#include <boost/range/iterator_range.hpp>
#include <boost/iterator/iterator_adaptor.hpp>
#include <iterator>
namespace boost
{
namespace range_detail
{
// strided_iterator for wrapping a forward traversal iterator
template<class BaseIterator, class Category>
class strided_iterator
: public iterator_adaptor<
strided_iterator<BaseIterator, Category>
, BaseIterator
, use_default
, boost::forward_traversal_tag
>
{
friend class ::boost::iterator_core_access;
typedef iterator_adaptor<
strided_iterator<BaseIterator, Category>
, BaseIterator
, use_default
, boost::forward_traversal_tag
> super_t;
public:
typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
typedef BaseIterator base_iterator;
strided_iterator()
: m_last()
, m_stride()
{
}
strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride)
: super_t(it)
, m_last(last)
, m_stride(stride)
{
}
template<class OtherIterator>
strided_iterator(const strided_iterator<OtherIterator, Category>& other,
BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0)
: super_t(other)
, m_last(other.base_end())
, m_stride(other.get_stride())
{
}
base_iterator base_end() const { return m_last; }
difference_type get_stride() const { return m_stride; }
private:
void increment()
{
base_iterator& it = this->base_reference();
for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i)
++it;
}
base_iterator m_last;
difference_type m_stride;
};
// strided_iterator for wrapping a bidirectional iterator
template<class BaseIterator>
class strided_iterator<BaseIterator, bidirectional_traversal_tag>
: public iterator_adaptor<
strided_iterator<BaseIterator, bidirectional_traversal_tag>
, BaseIterator
, use_default
, bidirectional_traversal_tag
>
{
friend class ::boost::iterator_core_access;
typedef iterator_adaptor<
strided_iterator<BaseIterator, bidirectional_traversal_tag>
, BaseIterator
, use_default
, bidirectional_traversal_tag
> super_t;
public:
typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
typedef BaseIterator base_iterator;
strided_iterator()
: m_first()
, m_last()
, m_stride()
{
}
strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride)
: super_t(it)
, m_first(first)
, m_last(last)
, m_stride(stride)
{
}
template<class OtherIterator>
strided_iterator(const strided_iterator<OtherIterator, bidirectional_traversal_tag>& other,
BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0)
: super_t(other.base())
, m_first(other.base_begin())
, m_last(other.base_end())
, m_stride(other.get_stride())
{
}
base_iterator base_begin() const { return m_first; }
base_iterator base_end() const { return m_last; }
difference_type get_stride() const { return m_stride; }
private:
void increment()
{
base_iterator& it = this->base_reference();
for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i)
++it;
}
void decrement()
{
base_iterator& it = this->base_reference();
for (difference_type i = 0; (it != m_first) && (i < m_stride); ++i)
--it;
}
base_iterator m_first;
base_iterator m_last;
difference_type m_stride;
};
// strided_iterator implementation for wrapping a random access iterator
template<class BaseIterator>
class strided_iterator<BaseIterator, random_access_traversal_tag>
: public iterator_adaptor<
strided_iterator<BaseIterator, random_access_traversal_tag>
, BaseIterator
, use_default
, random_access_traversal_tag
>
{
friend class ::boost::iterator_core_access;
typedef iterator_adaptor<
strided_iterator<BaseIterator, random_access_traversal_tag>
, BaseIterator
, use_default
, random_access_traversal_tag
> super_t;
public:
typedef BOOST_DEDUCED_TYPENAME super_t::difference_type difference_type;
typedef BaseIterator base_iterator;
strided_iterator()
: m_first()
, m_last()
, m_index(0)
, m_stride()
{
}
strided_iterator(BaseIterator first, BaseIterator it, BaseIterator last, difference_type stride)
: super_t(it)
, m_first(first)
, m_last(last)
, m_index(stride ? (it - first) / stride : 0)
, m_stride(stride)
{
}
template<class OtherIterator>
strided_iterator(const strided_iterator<OtherIterator, random_access_traversal_tag>& other,
BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0)
: super_t(other.base())
, m_first(other.base_begin())
, m_last(other.base_end())
, m_index(other.get_index())
, m_stride(other.get_stride())
{
}
base_iterator base_begin() const { return m_first; }
base_iterator base_end() const { return m_last; }
difference_type get_stride() const { return m_stride; }
difference_type get_index() const { return m_index; }
private:
void increment()
{
m_index += m_stride;
if (m_index < (m_last - m_first))
this->base_reference() = m_first + m_index;
else
this->base_reference() = m_last;
}
void decrement()
{
m_index -= m_stride;
if (m_index >= 0)
this->base_reference() = m_first + m_index;
else
this->base_reference() = m_first;
}
void advance(difference_type offset)
{
offset *= m_stride;
m_index += offset;
if (m_index < 0)
this->base_reference() = m_first;
else if (m_index > (m_last - m_first))
this->base_reference() = m_last;
else
this->base_reference() = m_first + m_index;
}
template<class OtherIterator>
difference_type distance_to(const strided_iterator<OtherIterator, random_access_traversal_tag>& other,
BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0) const
{
if (other.base() >= this->base())
return (other.base() - this->base() + (m_stride - 1)) / m_stride;
return (other.base() - this->base() - (m_stride - 1)) / m_stride;
}
bool equal(const strided_iterator& other) const
{
return this->base() == other.base();
}
private:
base_iterator m_first;
base_iterator m_last;
difference_type m_index;
difference_type m_stride;
};
template<class BaseIterator, class Difference> inline
strided_iterator<BaseIterator, BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type>
make_strided_iterator(BaseIterator first, BaseIterator it,
BaseIterator last, Difference stride)
{
BOOST_ASSERT( stride >= 0 );
typedef BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type traversal_tag;
return strided_iterator<BaseIterator, traversal_tag>(first, it, last, stride);
}
template< class Rng
, class Category = BOOST_DEDUCED_TYPENAME iterator_traversal<
BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type
>::type
>
class strided_range
: public iterator_range<
range_detail::strided_iterator<
BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type,
Category
>
>
{
typedef range_detail::strided_iterator<
BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type,
Category
> iter_type;
typedef iterator_range<iter_type> super_t;
public:
template<class Difference>
strided_range(Difference stride, Rng& rng)
: super_t(make_strided_iterator(boost::begin(rng), boost::begin(rng), boost::end(rng), stride),
make_strided_iterator(boost::begin(rng), boost::end(rng), boost::end(rng), stride))
{
BOOST_ASSERT( stride >= 0 );
}
};
template<class Difference>
class strided_holder : public holder<Difference>
{
public:
explicit strided_holder(Difference value) : holder<Difference>(value) {}
};
template<class Rng, class Difference>
inline strided_range<Rng>
operator|(Rng& rng, const strided_holder<Difference>& stride)
{
return strided_range<Rng>(stride.val, rng);
}
template<class Rng, class Difference>
inline strided_range<const Rng>
operator|(const Rng& rng, const strided_holder<Difference>& stride)
{
return strided_range<const Rng>(stride.val, rng);
}
} // namespace range_detail
using range_detail::strided_range;
namespace adaptors
{
namespace
{
const range_detail::forwarder<range_detail::strided_holder>
strided = range_detail::forwarder<range_detail::strided_holder>();
}
template<class Range, class Difference>
inline strided_range<Range>
stride(Range& rng, Difference step)
{
return strided_range<Range>(step, rng);
}
template<class Range, class Difference>
inline strided_range<const Range>
stride(const Range& rng, Difference step)
{
return strided_range<const Range>(step, rng);
}
} // namespace 'adaptors'
} // namespace 'boost'
#endif
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