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@gmail.com>
5 // Copyright (C) 2008 Gael Guennebaud <gael.guennebaud@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