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/*
* Copyright 2008-2013 NVIDIA Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*! \file thrust/iterator/reverse_iterator.h
* \brief An iterator adaptor which adapts another iterator to traverse backwards
*/
/*
* (C) Copyright David Abrahams 2002.
* (C) Copyright Jeremy Siek 2002.
* (C) Copyright Thomas Witt 2002.
*
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying NOTICE file for the complete license)
*
* For more information, see http://www.boost.org
*/
#pragma once
#include <thrust/detail/config.h>
#include <thrust/detail/type_traits.h>
#include <thrust/iterator/detail/reverse_iterator_base.h>
#include <thrust/iterator/iterator_facade.h>
THRUST_NAMESPACE_BEGIN
/*! \addtogroup iterators
* \{
*/
/*! \addtogroup fancyiterator Fancy Iterators
* \ingroup iterators
* \{
*/
/*! \p reverse_iterator is an iterator which represents a pointer into a
* reversed view of a given range. In this way, \p reverse_iterator allows
* backwards iteration through a bidirectional input range.
*
* It is important to note that although \p reverse_iterator is constructed
* from a given iterator, it points to the element preceding it. In this way,
* the past-the-end \p reverse_iterator of a given range points to the element
* preceding the first element of the input range. By the same token, the first
* \p reverse_iterator of a given range is constructed from a past-the-end iterator
* of the original range yet points to the last element of the input.
*
* The following code snippet demonstrates how to create a \p reverse_iterator
* which represents a reversed view of the contents of a \p device_vector.
*
* \code
* #include <thrust/iterator/reverse_iterator.h>
* #include <thrust/device_vector.h>
* ...
* thrust::device_vector<float> v(4);
* v[0] = 0.0f;
* v[1] = 1.0f;
* v[2] = 2.0f;
* v[3] = 3.0f;
*
* typedef thrust::device_vector<float>::iterator Iterator;
*
* // note that we point the iterator to the *end* of the device_vector
* thrust::reverse_iterator<Iterator> iter(values.end());
*
* *iter; // returns 3.0f;
* iter[0]; // returns 3.0f;
* iter[1]; // returns 2.0f;
* iter[2]; // returns 1.0f;
* iter[3]; // returns 0.0f;
*
* // iter[4] is an out-of-bounds error
* \endcode
*
* Since reversing a range is a common operation, containers like \p device_vector
* have nested typedefs for declaration shorthand and methods for constructing
* reverse_iterators. The following code snippet is equivalent to the previous:
*
* \code
* #include <thrust/device_vector.h>
* ...
* thrust::device_vector<float> v(4);
* v[0] = 0.0f;
* v[1] = 1.0f;
* v[2] = 2.0f;
* v[3] = 3.0f;
*
* // we use the nested type reverse_iterator to refer to a reversed view of
* // a device_vector and the method rbegin() to create a reverse_iterator pointing
* // to the beginning of the reversed device_vector
* thrust::device_iterator<float>::reverse_iterator iter = values.rbegin();
*
* *iter; // returns 3.0f;
* iter[0]; // returns 3.0f;
* iter[1]; // returns 2.0f;
* iter[2]; // returns 1.0f;
* iter[3]; // returns 0.0f;
*
* // iter[4] is an out-of-bounds error
*
* // similarly, rend() points to the end of the reversed sequence:
* assert(values.rend() == (iter + 4));
* \endcode
*
* Finally, the following code snippet demonstrates how to use reverse_iterator to
* perform a reversed prefix sum operation on the contents of a device_vector:
*
* \code
* #include <thrust/device_vector.h>
* #include <thrust/scan.h>
* ...
* thrust::device_vector<int> v(5);
* v[0] = 0;
* v[1] = 1;
* v[2] = 2;
* v[3] = 3;
* v[4] = 4;
*
* thrust::device_vector<int> result(5);
*
* // exclusive scan v into result in reverse
* thrust::exclusive_scan(v.rbegin(), v.rend(), result.begin());
*
* // result is now {0, 4, 7, 9, 10}
* \endcode
*
* \see make_reverse_iterator
*/
template<typename BidirectionalIterator>
class reverse_iterator
: public detail::reverse_iterator_base<BidirectionalIterator>::type
{
/*! \cond
*/
private:
typedef typename thrust::detail::reverse_iterator_base<
BidirectionalIterator
>::type super_t;
friend class thrust::iterator_core_access;
/*! \endcond
*/
public:
/*! Default constructor does nothing.
*/
__host__ __device__
reverse_iterator() {}
/*! \p Constructor accepts a \c BidirectionalIterator pointing to a range
* for this \p reverse_iterator to reverse.
*
* \param x A \c BidirectionalIterator pointing to a range to reverse.
*/
__host__ __device__
explicit reverse_iterator(BidirectionalIterator x);
/*! \p Copy constructor allows construction from a related compatible
* \p reverse_iterator.
*
* \param r A \p reverse_iterator to copy from.
*/
template<typename OtherBidirectionalIterator>
__host__ __device__
reverse_iterator(reverse_iterator<OtherBidirectionalIterator> const &r
// XXX msvc screws this up
// XXX remove these guards when we have static_assert
#if THRUST_HOST_COMPILER != THRUST_HOST_COMPILER_MSVC
, typename thrust::detail::enable_if<
thrust::detail::is_convertible<
OtherBidirectionalIterator,
BidirectionalIterator
>::value
>::type * = 0
#endif // MSVC
);
/*! \cond
*/
private:
__thrust_exec_check_disable__
__host__ __device__
typename super_t::reference dereference() const;
__host__ __device__
void increment();
__host__ __device__
void decrement();
__host__ __device__
void advance(typename super_t::difference_type n);
template<typename OtherBidirectionalIterator>
__host__ __device__
typename super_t::difference_type
distance_to(reverse_iterator<OtherBidirectionalIterator> const &y) const;
/*! \endcond
*/
}; // end reverse_iterator
/*! \p make_reverse_iterator creates a \p reverse_iterator
* from a \c BidirectionalIterator pointing to a range of elements to reverse.
*
* \param x A \c BidirectionalIterator pointing to a range to reverse.
* \return A new \p reverse_iterator which reverses the range \p x.
*/
template<typename BidirectionalIterator>
__host__ __device__
reverse_iterator<BidirectionalIterator> make_reverse_iterator(BidirectionalIterator x);
/*! \} // end fancyiterators
*/
/*! \} // end iterators
*/
THRUST_NAMESPACE_END
#include <thrust/iterator/detail/reverse_iterator.inl>
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