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     PlainObjectTypeInnerSize = ((traits<PlainObjectType>::Flags&RowMajorBit)==RowMajorBit)
24                              ? PlainObjectType::ColsAtCompileTime
25                              : PlainObjectType::RowsAtCompileTime,
26 
27     InnerStrideAtCompileTime = StrideType::InnerStrideAtCompileTime == 0
28                              ? int(PlainObjectType::InnerStrideAtCompileTime)
29                              : int(StrideType::InnerStrideAtCompileTime),
30     OuterStrideAtCompileTime = StrideType::OuterStrideAtCompileTime == 0
31                              ? (InnerStrideAtCompileTime==Dynamic || PlainObjectTypeInnerSize==Dynamic
32                                 ? Dynamic
33                                 : int(InnerStrideAtCompileTime) * int(PlainObjectTypeInnerSize))
34                              : int(StrideType::OuterStrideAtCompileTime),
35     Alignment = int(MapOptions)&int(AlignedMask),
36     Flags0 = TraitsBase::Flags & (~NestByRefBit),
37     Flags = is_lvalue<PlainObjectType>::value ? int(Flags0) : (int(Flags0) & ~LvalueBit)
38   };
39 private:
40   enum { Options }; // Expressions don't have Options
41 };
42 }
43 
44 /** \class Map
45   * \ingroup Core_Module
46   *
47   * \brief A matrix or vector expression mapping an existing array of data.
48   *
49   * \tparam PlainObjectType the equivalent matrix type of the mapped data
50   * \tparam MapOptions specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned.
51   *                The default is \c #Unaligned.
52   * \tparam StrideType optionally specifies strides. By default, Map assumes the memory layout
53   *                   of an ordinary, contiguous array. This can be overridden by specifying strides.
54   *                   The type passed here must be a specialization of the Stride template, see examples below.
55   *
56   * This class represents a matrix or vector expression mapping an existing array of data.
57   * It can be used to let Eigen interface without any overhead with non-Eigen data structures,
58   * such as plain C arrays or structures from other libraries. By default, it assumes that the
59   * data is laid out contiguously in memory. You can however override this by explicitly specifying
60   * inner and outer strides.
61   *
62   * Here's an example of simply mapping a contiguous array as a \ref TopicStorageOrders "column-major" matrix:
63   * \include Map_simple.cpp
64   * Output: \verbinclude Map_simple.out
65   *
66   * If you need to map non-contiguous arrays, you can do so by specifying strides:
67   *
68   * Here's an example of mapping an array as a vector, specifying an inner stride, that is, the pointer
69   * increment between two consecutive coefficients. Here, we're specifying the inner stride as a compile-time
70   * fixed value.
71   * \include Map_inner_stride.cpp
72   * Output: \verbinclude Map_inner_stride.out
73   *
74   * Here's an example of mapping an array while specifying an outer stride. Here, since we're mapping
75   * as a column-major matrix, 'outer stride' means the pointer increment between two consecutive columns.
76   * Here, we're specifying the outer stride as a runtime parameter. Note that here \c OuterStride<> is
77   * a short version of \c OuterStride<Dynamic> because the default template parameter of OuterStride
78   * is  \c Dynamic
79   * \include Map_outer_stride.cpp
80   * Output: \verbinclude Map_outer_stride.out
81   *
82   * For more details and for an example of specifying both an inner and an outer stride, see class Stride.
83   *
84   * \b Tip: to change the array of data mapped by a Map object, you can use the C++
85   * placement new syntax:
86   *
87   * Example: \include Map_placement_new.cpp
88   * Output: \verbinclude Map_placement_new.out
89   *
90   * This class is the return type of PlainObjectBase::Map() but can also be used directly.
91   *
92   * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
93   */
94 template<typename PlainObjectType, int MapOptions, typename StrideType> class Map
95   : public MapBase<Map<PlainObjectType, MapOptions, StrideType> >
96 {
97   public:
98 
99     typedef MapBase<Map> Base;
100     EIGEN_DENSE_PUBLIC_INTERFACE(Map)
101 
102     typedef typename Base::PointerType PointerType;
103     typedef PointerType PointerArgType;
104     EIGEN_DEVICE_FUNC
105     inline PointerType cast_to_pointer_type(PointerArgType ptr) { return ptr; }
106 
107     EIGEN_DEVICE_FUNC
108     inline Index innerStride() const
109     {
110       return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
111     }
112 
113     EIGEN_DEVICE_FUNC
114     inline Index outerStride() const
115     {
116       return int(StrideType::OuterStrideAtCompileTime) != 0 ? m_stride.outer()
117            : int(internal::traits<Map>::OuterStrideAtCompileTime) != Dynamic ? Index(internal::traits<Map>::OuterStrideAtCompileTime)
118            : IsVectorAtCompileTime ? (this->size() * innerStride())
119            : (int(Flags)&RowMajorBit) ? (this->cols() * innerStride())
120            : (this->rows() * innerStride());
121     }
122 
123     /** Constructor in the fixed-size case.
124       *
125       * \param dataPtr pointer to the array to map
126       * \param stride optional Stride object, passing the strides.
127       */
128     EIGEN_DEVICE_FUNC
129     explicit inline Map(PointerArgType dataPtr, const StrideType& stride = StrideType())
130       : Base(cast_to_pointer_type(dataPtr)), m_stride(stride)
131     {
132       PlainObjectType::Base::_check_template_params();
133     }
134 
135     /** Constructor in the dynamic-size vector case.
136       *
137       * \param dataPtr pointer to the array to map
138       * \param size the size of the vector expression
139       * \param stride optional Stride object, passing the strides.
140       */
141     EIGEN_DEVICE_FUNC
142     inline Map(PointerArgType dataPtr, Index size, const StrideType& stride = StrideType())
143       : Base(cast_to_pointer_type(dataPtr), size), m_stride(stride)
144     {
145       PlainObjectType::Base::_check_template_params();
146     }
147 
148     /** Constructor in the dynamic-size matrix case.
149       *
150       * \param dataPtr pointer to the array to map
151       * \param rows the number of rows of the matrix expression
152       * \param cols the number of columns of the matrix expression
153       * \param stride optional Stride object, passing the strides.
154       */
155     EIGEN_DEVICE_FUNC
156     inline Map(PointerArgType dataPtr, Index rows, Index cols, const StrideType& stride = StrideType())
157       : Base(cast_to_pointer_type(dataPtr), rows, cols), m_stride(stride)
158     {
159       PlainObjectType::Base::_check_template_params();
160     }
161 
162     EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Map)
163 
164   protected:
165     StrideType m_stride;
166 };
167 
168 
169 } // end namespace Eigen
170 
171 #endif // EIGEN_MAP_H
172