tex_obj_input_iterator.cuh

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 * Copyright (c) 2011, Duane Merrill.  All rights reserved.
 * Copyright (c) 2011-2018, NVIDIA CORPORATION.  All rights reserved.
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 *       names of its contributors may be used to endorse or promote products
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#pragma once

#include <iterator>
#include <iostream>

#include "../thread/thread_load.cuh"
#include "../thread/thread_store.cuh"
#include "../util_device.cuh"
#include "../util_debug.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


CUB_NS_PREFIX

namespace cub {

template <
    typename    T,
    typename    OffsetT = ptrdiff_t>
class TexObjInputIterator
{
public:

    // Required iterator traits
    typedef TexObjInputIterator                 self_type;              
    typedef OffsetT                             difference_type;        
    typedef T                                   value_type;             
    typedef T*                                  pointer;                
    typedef T                                   reference;              

#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;                                        
#else
    typedef std::random_access_iterator_tag     iterator_category;      
#endif  // THRUST_VERSION

private:

    // Largest texture word we can use in device
    typedef typename UnitWord<T>::TextureWord TextureWord;

    // Number of texture words per T
    enum {
        TEXTURE_MULTIPLE = sizeof(T) / sizeof(TextureWord)
    };

private:

    T*                  ptr;
    difference_type     tex_offset;
    cudaTextureObject_t tex_obj;

public:

    __host__ __device__ __forceinline__ TexObjInputIterator()
    :
        ptr(NULL),
        tex_offset(0),
        tex_obj(0)
    {}

    template <typename QualifiedT>
    cudaError_t BindTexture(
        QualifiedT      *ptr,               
        size_t          bytes = size_t(-1),         
        size_t          tex_offset = 0)     
    {
        this->ptr = const_cast<typename RemoveQualifiers<QualifiedT>::Type *>(ptr);
        this->tex_offset = tex_offset;

        cudaChannelFormatDesc   channel_desc = cudaCreateChannelDesc<TextureWord>();
        cudaResourceDesc        res_desc;
        cudaTextureDesc         tex_desc;
        memset(&res_desc, 0, sizeof(cudaResourceDesc));
        memset(&tex_desc, 0, sizeof(cudaTextureDesc));
        res_desc.resType                = cudaResourceTypeLinear;
        res_desc.res.linear.devPtr      = this->ptr;
        res_desc.res.linear.desc        = channel_desc;
        res_desc.res.linear.sizeInBytes = bytes;
        tex_desc.readMode               = cudaReadModeElementType;
        return cudaCreateTextureObject(&tex_obj, &res_desc, &tex_desc, NULL);
    }

    cudaError_t UnbindTexture()
    {
        return cudaDestroyTextureObject(tex_obj);
    }

    __host__ __device__ __forceinline__ self_type operator++(int)
    {
        self_type retval = *this;
        tex_offset++;
        return retval;
    }

    __host__ __device__ __forceinline__ self_type operator++()
    {
        tex_offset++;
        return *this;
    }

    __host__ __device__ __forceinline__ reference operator*() const
    {
#if (CUB_PTX_ARCH == 0)
        // Simply dereference the pointer on the host
        return ptr[tex_offset];
#else
        // Move array of uninitialized words, then alias and assign to return value
        TextureWord words[TEXTURE_MULTIPLE];

        #pragma unroll
        for (int i = 0; i < TEXTURE_MULTIPLE; ++i)
        {
            words[i] = tex1Dfetch<TextureWord>(
                tex_obj,
                (tex_offset * TEXTURE_MULTIPLE) + i);
        }

        // Load from words
        return *reinterpret_cast<T*>(words);
#endif
    }

    template <typename Distance>
    __host__ __device__ __forceinline__ self_type operator+(Distance n) const
    {
        self_type retval;
        retval.ptr          = ptr;
        retval.tex_obj      = tex_obj;
        retval.tex_offset   = tex_offset + n;
        return retval;
    }

    template <typename Distance>
    __host__ __device__ __forceinline__ self_type& operator+=(Distance n)
    {
        tex_offset += n;
        return *this;
    }

    template <typename Distance>
    __host__ __device__ __forceinline__ self_type operator-(Distance n) const
    {
        self_type retval;
        retval.ptr          = ptr;
        retval.tex_obj      = tex_obj;
        retval.tex_offset   = tex_offset - n;
        return retval;
    }

    template <typename Distance>
    __host__ __device__ __forceinline__ self_type& operator-=(Distance n)
    {
        tex_offset -= n;
        return *this;
    }

    __host__ __device__ __forceinline__ difference_type operator-(self_type other) const
    {
        return tex_offset - other.tex_offset;
    }

    template <typename Distance>
    __host__ __device__ __forceinline__ reference operator[](Distance n) const
    {
        self_type offset = (*this) + n;
        return *offset;
    }

    __host__ __device__ __forceinline__ pointer operator->()
    {
        return &(*(*this));
    }

    __host__ __device__ __forceinline__ bool operator==(const self_type& rhs)
    {
        return ((ptr == rhs.ptr) && (tex_offset == rhs.tex_offset) && (tex_obj == rhs.tex_obj));
    }

    __host__ __device__ __forceinline__ bool operator!=(const self_type& rhs)
    {
        return ((ptr != rhs.ptr) || (tex_offset != rhs.tex_offset) || (tex_obj != rhs.tex_obj));
    }

    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)