/******************************************************************************
   * Copyright (c) 2011, Duane Merrill.  All rights reserved.
   * Copyright (c) 2011-2018, NVIDIA CORPORATION.  All rights reserved.
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  /**
   * \file
   * Random-access iterator types
   */
  
  #pragma once
  
  #include <iterator>
  #include <iostream>
  
  #include "../thread/thread_load.cuh"
  #include "../thread/thread_store.cuh"
  #include "../util_device.cuh"
  #include "../util_namespace.cuh"
  
  #if (THRUST_VERSION >= 100700)
      // This iterator is compatible with Thrust API 1.7 and newer
      #include <thrust/iterator/iterator_facade.h>
      #include <thrust/iterator/iterator_traits.h>
  #endif // THRUST_VERSION
  
  
  /// Optional outer namespace(s)
  CUB_NS_PREFIX
  
  /// CUB namespace
  namespace cub {
  
  
  /**
   * \addtogroup UtilIterator
   * @{
   */
  
  
  /**
   * \brief A random-access output wrapper for storing array values using a PTX cache-modifier.
   *
   * \par Overview
   * - CacheModifiedOutputIterator is a random-access output iterator that wraps a native
   *   device pointer of type <tt>ValueType*</tt>. \p ValueType references are
   *   made by writing \p ValueType values through stores modified by \p MODIFIER.
   * - Can be used to store any data type to memory using PTX cache store modifiers (e.g., "STORE_WB",
   *   "STORE_CG", "STORE_CS", "STORE_WT", etc.).
   * - Can be constructed, manipulated, and exchanged within and between host and device
   *   functions, but can only be dereferenced within device functions.
   * - Compatible with Thrust API v1.7 or newer.
   *
   * \par Snippet
   * The code snippet below illustrates the use of \p CacheModifiedOutputIterator to
   * dereference a device array of doubles using the "wt" PTX load modifier
   * (i.e., write-through to system memory).
   * \par
   * \code
   * #include <cub/cub.cuh>   // or equivalently <cub/iterator/cache_modified_output_iterator.cuh>
   *
   * // Declare, allocate, and initialize a device array
   * double *d_out;              // e.g., [, , , , , , ]
   *
   * // Create an iterator wrapper
   * cub::CacheModifiedOutputIterator<cub::STORE_WT, double> itr(d_out);
   *
   * // Within device code:
   * itr[0]  = 8.0;
   * itr[1]  = 66.0;
   * itr[55] = 24.0;
   *
   * \endcode
   *
   * \par Usage Considerations
   * - Can only be dereferenced within device code
   *
   * \tparam CacheStoreModifier     The cub::CacheStoreModifier to use when accessing data
   * \tparam ValueType            The value type of this iterator
   * \tparam OffsetT              The difference type of this iterator (Default: \p ptrdiff_t)
   */
  template <
      CacheStoreModifier  MODIFIER,
      typename            ValueType,
      typename            OffsetT = ptrdiff_t>
  class CacheModifiedOutputIterator
  {
  private:
  
      // Proxy object
      struct Reference
      {
          ValueType* ptr;
  
          /// Constructor
          __host__ __device__ __forceinline__ Reference(ValueType* ptr) : ptr(ptr) {}
  
          /// Assignment
          __device__ __forceinline__ ValueType operator =(ValueType val)
          {
              ThreadStore<MODIFIER>(ptr, val);
              return val;
          }
      };
  
  public:
  
      // Required iterator traits
      typedef CacheModifiedOutputIterator         self_type;              ///< My own type
      typedef OffsetT                             difference_type;        ///< Type to express the result of subtracting one iterator from another
      typedef void                                value_type;             ///< The type of the element the iterator can point to
      typedef void                                pointer;                ///< The type of a pointer to an element the iterator can point to
      typedef Reference                           reference;              ///< The type of a reference to an element the iterator can point to
  
  #if (THRUST_VERSION >= 100700)
      // Use Thrust's iterator categories so we can use these iterators in Thrust 1.7 (or newer) methods
      typedef typename thrust::detail::iterator_facade_category<
          thrust::device_system_tag,
          thrust::random_access_traversal_tag,
          value_type,
          reference
        >::type iterator_category;                                        ///< The iterator category
  #else
      typedef std::random_access_iterator_tag     iterator_category;      ///< The iterator category
  #endif  // THRUST_VERSION
  
  private:
  
      ValueType* ptr;
  
  public:
  
      /// Constructor
      template <typename QualifiedValueType>
      __host__ __device__ __forceinline__ CacheModifiedOutputIterator(
          QualifiedValueType* ptr)     ///< Native pointer to wrap
      :
          ptr(const_cast<typename RemoveQualifiers<QualifiedValueType>::Type *>(ptr))
      {}
  
      /// Postfix increment
      __host__ __device__ __forceinline__ self_type operator++(int)
      {
          self_type retval = *this;
          ptr++;
          return retval;
      }
  
  
      /// Prefix increment
      __host__ __device__ __forceinline__ self_type operator++()
      {
          ptr++;
          return *this;
      }
  
      /// Indirection
      __host__ __device__ __forceinline__ reference operator*() const
      {
          return Reference(ptr);
      }
  
      /// Addition
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type operator+(Distance n) const
      {
          self_type retval(ptr + n);
          return retval;
      }
  
      /// Addition assignment
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type& operator+=(Distance n)
      {
          ptr += n;
          return *this;
      }
  
      /// Subtraction
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type operator-(Distance n) const
      {
          self_type retval(ptr - n);
          return retval;
      }
  
      /// Subtraction assignment
      template <typename Distance>
      __host__ __device__ __forceinline__ self_type& operator-=(Distance n)
      {
          ptr -= n;
          return *this;
      }
  
      /// Distance
      __host__ __device__ __forceinline__ difference_type operator-(self_type other) const
      {
          return ptr - other.ptr;
      }
  
      /// Array subscript
      template <typename Distance>
      __host__ __device__ __forceinline__ reference operator[](Distance n) const
      {
          return Reference(ptr + n);
      }
  
      /// Equal to
      __host__ __device__ __forceinline__ bool operator==(const self_type& rhs)
      {
          return (ptr == rhs.ptr);
      }
  
      /// Not equal to
      __host__ __device__ __forceinline__ bool operator!=(const self_type& rhs)
      {
          return (ptr != rhs.ptr);
      }
  
      /// ostream operator
      friend std::ostream& operator<<(std::ostream& os, const self_type& itr)
      {
          return os;
      }
  };
  
  
  /** @} */       // end group UtilIterator
  
  }               // CUB namespace
  CUB_NS_POSTFIX  // Optional outer namespace(s)