forked from boostorg/range
[boost][range] - Corrected yesterdays erroneous modifications to the strided adaptor.
[SVN r67445]
This commit is contained in:
@ -16,68 +16,119 @@
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#include <boost/iterator/iterator_adaptor.hpp>
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#include <iterator>
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#include <iostream>
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namespace boost
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{
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namespace range_detail
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{
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template<typename BaseIterator>
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template<class BaseIterator>
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class strided_iterator
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: public iterator_adaptor<
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strided_iterator<BaseIterator>,
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BaseIterator>
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strided_iterator<BaseIterator>
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, BaseIterator
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>
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{
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friend class iterator_core_access;
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typedef iterator_adaptor<strided_iterator<BaseIterator>, BaseIterator> super_t;
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public:
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typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
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typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
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strided_iterator() : m_stride() { }
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strided_iterator()
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: m_stride(), m_offset(), m_max_offset()
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{
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}
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strided_iterator(const strided_iterator& other)
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: super_t(other), m_stride(other.m_stride) { }
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explicit strided_iterator(BaseIterator base_it,
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difference_type stride,
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difference_type offset,
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difference_type max_offset)
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: super_t(base_it)
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, m_stride(stride)
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, m_offset(offset)
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, m_max_offset(max_offset)
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{
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}
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explicit strided_iterator(BaseIterator base_it, difference_type stride)
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: super_t(base_it), m_stride(stride) { }
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template<class OtherIterator>
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strided_iterator(const strided_iterator<OtherIterator>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0)
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: super_t(other)
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, m_stride(other.m_stride)
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, m_offset(other.m_offset)
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, m_max_offset(other.m_max_offset)
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{
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}
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strided_iterator&
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operator=(const strided_iterator& other)
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{
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super_t::operator=(other);
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// Is the interoperation of the stride safe?
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m_stride = other.m_stride;
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m_offset = other.m_offset;
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m_max_offset = other.m_max_offset;
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return *this;
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}
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void increment() { std::advance(this->base_reference(), m_stride); }
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void increment()
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{
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m_offset += m_stride;
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if (m_offset <= m_max_offset)
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std::advance(this->base_reference(), m_stride);
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}
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void decrement() { std::advance(this->base_reference(), -m_stride); }
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void decrement()
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{
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m_offset -= m_stride;
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if (m_offset >= 0)
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std::advance(this->base_reference(), -m_stride);
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}
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void advance(difference_type n) { std::advance(this->base_reference(), n * m_stride); }
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void advance(difference_type n)
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{
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n *= m_stride;
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m_offset += n;
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if (m_offset >= 0 && m_offset <= m_max_offset)
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std::advance(this->base_reference(), n);
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}
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template<class OtherIterator>
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bool equal(const strided_iterator<OtherIterator>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0) const
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{
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return m_offset == other.m_offset;
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}
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difference_type
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distance_to(const strided_iterator& other) const
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{
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return std::distance(this->base_reference(), other.base_reference()) / m_stride;
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return (other.m_offset - m_offset) / m_stride;
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}
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// Using the compiler generated copy constructor and
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// and assignment operator
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private:
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difference_type m_stride;
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difference_type m_offset;
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difference_type m_max_offset;
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};
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template<class BaseIterator> inline
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template<class BaseIterator, class Difference> inline
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strided_iterator<BaseIterator>
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make_strided_iterator(
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const BaseIterator& first,
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BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type stride)
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Difference stride,
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typename std::iterator_traits<BaseIterator>::difference_type offset,
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typename std::iterator_traits<BaseIterator>::difference_type max_offset
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)
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{
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return strided_iterator<BaseIterator>(first, stride);
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BOOST_ASSERT( stride >= 0 );
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BOOST_ASSERT( (stride == 0) || (offset % stride == 0) );
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BOOST_ASSERT( (stride == 0) || (max_offset % stride == 0) );
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BOOST_ASSERT( offset <= max_offset );
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return strided_iterator<BaseIterator>(first, stride, offset, max_offset);
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}
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template< class Rng >
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@ -87,33 +138,33 @@ namespace boost
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typedef range_detail::strided_iterator<BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type> iter_type;
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typedef iterator_range<iter_type> super_t;
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public:
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template< typename Difference >
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template<class Difference>
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strided_range(Difference stride, Rng& rng)
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: super_t(make_first(rng, stride), make_last(rng, stride))
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: super_t(make_super(stride, rng))
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{
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BOOST_ASSERT( stride >= 0 );
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}
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private:
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template<typename Difference>
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static iter_type make_first(Rng& rng, Difference stride)
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template<class Difference>
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static super_t make_super(const Difference stride, Rng& rng)
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{
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return make_strided_iterator(boost::begin(rng), stride);
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const Difference count = boost::size(rng);
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const Difference max_count = max_offset(count, stride);
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return super_t(make_strided_iterator(boost::begin(rng), stride, 0, max_count),
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make_strided_iterator(boost::end(rng), stride, max_count, max_count));
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}
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template<typename Difference>
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static iter_type make_last(Rng& rng, Difference stride)
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template<class Difference, class Stride>
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static Difference max_offset(Difference sz, const Stride stride)
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{
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typedef BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type raw_iter_t;
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typedef BOOST_DEDUCED_TYPENAME range_difference<Rng>::type diff_t;
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if (stride > 0)
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{
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raw_iter_t it = boost::end(rng);
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const diff_t count = boost::size(rng);
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std::advance(it, -(count % stride));
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return iter_type(it, stride);
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sz += stride - 1;
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sz /= stride;
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sz *= stride;
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}
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return make_strided_iterator(boost::end(rng), stride);
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return sz;
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}
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};
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