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      1 // This file is part of Eigen, a lightweight C++ template library
      2 // for linear algebra.
      3 //
      4 // Copyright (C) 2007-2010 Benoit Jacob <jacob.benoit.1 (at) gmail.com>
      5 // Copyright (C) 2008 Gael Guennebaud <gael.guennebaud (at) inria.fr>
      6 //
      7 // This Source Code Form is subject to the terms of the Mozilla
      8 // Public License v. 2.0. If a copy of the MPL was not distributed
      9 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
     10 
     11 #ifndef EIGEN_MAP_H
     12 #define EIGEN_MAP_H
     13 
     14 namespace Eigen {
     15 
     16 namespace internal {
     17 template<typename PlainObjectType, int MapOptions, typename StrideType>
     18 struct traits<Map<PlainObjectType, MapOptions, StrideType> >
     19   : public traits<PlainObjectType>
     20 {
     21   typedef traits<PlainObjectType> TraitsBase;
     22   enum {
     23     InnerStrideAtCompileTime = StrideType::InnerStrideAtCompileTime == 0
     24                              ? int(PlainObjectType::InnerStrideAtCompileTime)
     25                              : int(StrideType::InnerStrideAtCompileTime),
     26     OuterStrideAtCompileTime = StrideType::OuterStrideAtCompileTime == 0
     27                              ? int(PlainObjectType::OuterStrideAtCompileTime)
     28                              : int(StrideType::OuterStrideAtCompileTime),
     29     Alignment = int(MapOptions)&int(AlignedMask),
     30     Flags0 = TraitsBase::Flags & (~NestByRefBit),
     31     Flags = is_lvalue<PlainObjectType>::value ? int(Flags0) : (int(Flags0) & ~LvalueBit)
     32   };
     33 private:
     34   enum { Options }; // Expressions don't have Options
     35 };
     36 }
     37 
     38 /** \class Map
     39   * \ingroup Core_Module
     40   *
     41   * \brief A matrix or vector expression mapping an existing array of data.
     42   *
     43   * \tparam PlainObjectType the equivalent matrix type of the mapped data
     44   * \tparam MapOptions specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned.
     45   *                The default is \c #Unaligned.
     46   * \tparam StrideType optionally specifies strides. By default, Map assumes the memory layout
     47   *                   of an ordinary, contiguous array. This can be overridden by specifying strides.
     48   *                   The type passed here must be a specialization of the Stride template, see examples below.
     49   *
     50   * This class represents a matrix or vector expression mapping an existing array of data.
     51   * It can be used to let Eigen interface without any overhead with non-Eigen data structures,
     52   * such as plain C arrays or structures from other libraries. By default, it assumes that the
     53   * data is laid out contiguously in memory. You can however override this by explicitly specifying
     54   * inner and outer strides.
     55   *
     56   * Here's an example of simply mapping a contiguous array as a \ref TopicStorageOrders "column-major" matrix:
     57   * \include Map_simple.cpp
     58   * Output: \verbinclude Map_simple.out
     59   *
     60   * If you need to map non-contiguous arrays, you can do so by specifying strides:
     61   *
     62   * Here's an example of mapping an array as a vector, specifying an inner stride, that is, the pointer
     63   * increment between two consecutive coefficients. Here, we're specifying the inner stride as a compile-time
     64   * fixed value.
     65   * \include Map_inner_stride.cpp
     66   * Output: \verbinclude Map_inner_stride.out
     67   *
     68   * Here's an example of mapping an array while specifying an outer stride. Here, since we're mapping
     69   * as a column-major matrix, 'outer stride' means the pointer increment between two consecutive columns.
     70   * Here, we're specifying the outer stride as a runtime parameter. Note that here \c OuterStride<> is
     71   * a short version of \c OuterStride<Dynamic> because the default template parameter of OuterStride
     72   * is  \c Dynamic
     73   * \include Map_outer_stride.cpp
     74   * Output: \verbinclude Map_outer_stride.out
     75   *
     76   * For more details and for an example of specifying both an inner and an outer stride, see class Stride.
     77   *
     78   * \b Tip: to change the array of data mapped by a Map object, you can use the C++
     79   * placement new syntax:
     80   *
     81   * Example: \include Map_placement_new.cpp
     82   * Output: \verbinclude Map_placement_new.out
     83   *
     84   * This class is the return type of PlainObjectBase::Map() but can also be used directly.
     85   *
     86   * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
     87   */
     88 template<typename PlainObjectType, int MapOptions, typename StrideType> class Map
     89   : public MapBase<Map<PlainObjectType, MapOptions, StrideType> >
     90 {
     91   public:
     92 
     93     typedef MapBase<Map> Base;
     94     EIGEN_DENSE_PUBLIC_INTERFACE(Map)
     95 
     96     typedef typename Base::PointerType PointerType;
     97     typedef PointerType PointerArgType;
     98     EIGEN_DEVICE_FUNC
     99     inline PointerType cast_to_pointer_type(PointerArgType ptr) { return ptr; }
    100 
    101     EIGEN_DEVICE_FUNC
    102     inline Index innerStride() const
    103     {
    104       return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
    105     }
    106 
    107     EIGEN_DEVICE_FUNC
    108     inline Index outerStride() const
    109     {
    110       return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer()
    111            : IsVectorAtCompileTime ? this->size()
    112            : int(Flags)&RowMajorBit ? this->cols()
    113            : this->rows();
    114     }
    115 
    116     /** Constructor in the fixed-size case.
    117       *
    118       * \param dataPtr pointer to the array to map
    119       * \param stride optional Stride object, passing the strides.
    120       */
    121     EIGEN_DEVICE_FUNC
    122     explicit inline Map(PointerArgType dataPtr, const StrideType& stride = StrideType())
    123       : Base(cast_to_pointer_type(dataPtr)), m_stride(stride)
    124     {
    125       PlainObjectType::Base::_check_template_params();
    126     }
    127 
    128     /** Constructor in the dynamic-size vector case.
    129       *
    130       * \param dataPtr pointer to the array to map
    131       * \param size the size of the vector expression
    132       * \param stride optional Stride object, passing the strides.
    133       */
    134     EIGEN_DEVICE_FUNC
    135     inline Map(PointerArgType dataPtr, Index size, const StrideType& stride = StrideType())
    136       : Base(cast_to_pointer_type(dataPtr), size), m_stride(stride)
    137     {
    138       PlainObjectType::Base::_check_template_params();
    139     }
    140 
    141     /** Constructor in the dynamic-size matrix case.
    142       *
    143       * \param dataPtr pointer to the array to map
    144       * \param rows the number of rows of the matrix expression
    145       * \param cols the number of columns of the matrix expression
    146       * \param stride optional Stride object, passing the strides.
    147       */
    148     EIGEN_DEVICE_FUNC
    149     inline Map(PointerArgType dataPtr, Index rows, Index cols, const StrideType& stride = StrideType())
    150       : Base(cast_to_pointer_type(dataPtr), rows, cols), m_stride(stride)
    151     {
    152       PlainObjectType::Base::_check_template_params();
    153     }
    154 
    155     EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Map)
    156 
    157   protected:
    158     StrideType m_stride;
    159 };
    160 
    161 
    162 } // end namespace Eigen
    163 
    164 #endif // EIGEN_MAP_H
    165