Map.h revision 7faaa9f3f0df9d23790277834d426c3d992ac3ba 
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
14namespace Eigen {
15
16/** \class Map
17  * \ingroup Core_Module
18  *
19  * \brief A matrix or vector expression mapping an existing array of data.
20  *
21  * \tparam PlainObjectType the equivalent matrix type of the mapped data
22  * \tparam MapOptions specifies whether the pointer is \c #Aligned, or \c #Unaligned.
23  *                The default is \c #Unaligned.
24  * \tparam StrideType optionally specifies strides. By default, Map assumes the memory layout
25  *                   of an ordinary, contiguous array. This can be overridden by specifying strides.
26  *                   The type passed here must be a specialization of the Stride template, see examples below.
27  *
28  * This class represents a matrix or vector expression mapping an existing array of data.
29  * It can be used to let Eigen interface without any overhead with non-Eigen data structures,
30  * such as plain C arrays or structures from other libraries. By default, it assumes that the
31  * data is laid out contiguously in memory. You can however override this by explicitly specifying
32  * inner and outer strides.
33  *
34  * Here's an example of simply mapping a contiguous array as a \ref TopicStorageOrders "column-major" matrix:
35  * \include Map_simple.cpp
36  * Output: \verbinclude Map_simple.out
37  *
38  * If you need to map non-contiguous arrays, you can do so by specifying strides:
39  *
40  * Here's an example of mapping an array as a vector, specifying an inner stride, that is, the pointer
41  * increment between two consecutive coefficients. Here, we're specifying the inner stride as a compile-time
42  * fixed value.
43  * \include Map_inner_stride.cpp
44  * Output: \verbinclude Map_inner_stride.out
45  *
46  * Here's an example of mapping an array while specifying an outer stride. Here, since we're mapping
47  * as a column-major matrix, 'outer stride' means the pointer increment between two consecutive columns.
48  * Here, we're specifying the outer stride as a runtime parameter. Note that here \c OuterStride<> is
49  * a short version of \c OuterStride<Dynamic> because the default template parameter of OuterStride
50  * is  \c Dynamic
51  * \include Map_outer_stride.cpp
52  * Output: \verbinclude Map_outer_stride.out
53  *
54  * For more details and for an example of specifying both an inner and an outer stride, see class Stride.
55  *
56  * \b Tip: to change the array of data mapped by a Map object, you can use the C++
57  * placement new syntax:
58  *
59  * Example: \include Map_placement_new.cpp
60  * Output: \verbinclude Map_placement_new.out
61  *
62  * This class is the return type of PlainObjectBase::Map() but can also be used directly.
63  *
64  * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
65  */
66
67namespace internal {
68template<typename PlainObjectType, int MapOptions, typename StrideType>
69struct traits<Map<PlainObjectType, MapOptions, StrideType> >
70  : public traits<PlainObjectType>
71{
72  typedef traits<PlainObjectType> TraitsBase;
73  typedef typename PlainObjectType::Index Index;
74  typedef typename PlainObjectType::Scalar Scalar;
75  enum {
76    InnerStrideAtCompileTime = StrideType::InnerStrideAtCompileTime == 0
77                             ? int(PlainObjectType::InnerStrideAtCompileTime)
78                             : int(StrideType::InnerStrideAtCompileTime),
79    OuterStrideAtCompileTime = StrideType::OuterStrideAtCompileTime == 0
80                             ? int(PlainObjectType::OuterStrideAtCompileTime)
81                             : int(StrideType::OuterStrideAtCompileTime),
82    HasNoInnerStride = InnerStrideAtCompileTime == 1,
83    HasNoOuterStride = StrideType::OuterStrideAtCompileTime == 0,
84    HasNoStride = HasNoInnerStride && HasNoOuterStride,
85    IsAligned = bool(EIGEN_ALIGN) && ((int(MapOptions)&Aligned)==Aligned),
86    IsDynamicSize = PlainObjectType::SizeAtCompileTime==Dynamic,
87    KeepsPacketAccess = bool(HasNoInnerStride)
88                        && ( bool(IsDynamicSize)
89                           || HasNoOuterStride
90                           || ( OuterStrideAtCompileTime!=Dynamic
91                           && ((static_cast<int>(sizeof(Scalar))*OuterStrideAtCompileTime)%16)==0 ) ),
92    Flags0 = TraitsBase::Flags & (~NestByRefBit),
93    Flags1 = IsAligned ? (int(Flags0) | AlignedBit) : (int(Flags0) & ~AlignedBit),
94    Flags2 = (bool(HasNoStride) || bool(PlainObjectType::IsVectorAtCompileTime))
95           ? int(Flags1) : int(Flags1 & ~LinearAccessBit),
96    Flags3 = is_lvalue<PlainObjectType>::value ? int(Flags2) : (int(Flags2) & ~LvalueBit),
97    Flags = KeepsPacketAccess ? int(Flags3) : (int(Flags3) & ~PacketAccessBit)
98  };
99private:
100  enum { Options }; // Expressions don't have Options
101};
102}
103
104template<typename PlainObjectType, int MapOptions, typename StrideType> class Map
105  : public MapBase<Map<PlainObjectType, MapOptions, StrideType> >
106{
107  public:
108
109    typedef MapBase<Map> Base;
110    EIGEN_DENSE_PUBLIC_INTERFACE(Map)
111
112    typedef typename Base::PointerType PointerType;
113#if EIGEN2_SUPPORT_STAGE <= STAGE30_FULL_EIGEN3_API
114    typedef const Scalar* PointerArgType;
115    inline PointerType cast_to_pointer_type(PointerArgType ptr) { return const_cast<PointerType>(ptr); }
116#else
117    typedef PointerType PointerArgType;
118    inline PointerType cast_to_pointer_type(PointerArgType ptr) { return ptr; }
119#endif
120
121    inline Index innerStride() const
122    {
123      return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
124    }
125
126    inline Index outerStride() const
127    {
128      return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer()
129           : IsVectorAtCompileTime ? this->size()
130           : int(Flags)&RowMajorBit ? this->cols()
131           : this->rows();
132    }
133
134    /** Constructor in the fixed-size case.
135      *
136      * \param dataPtr pointer to the array to map
137      * \param a_stride optional Stride object, passing the strides.
138      */
139    inline Map(PointerArgType dataPtr, const StrideType& a_stride = StrideType())
140      : Base(cast_to_pointer_type(dataPtr)), m_stride(a_stride)
141    {
142      PlainObjectType::Base::_check_template_params();
143    }
144
145    /** Constructor in the dynamic-size vector case.
146      *
147      * \param dataPtr pointer to the array to map
148      * \param a_size the size of the vector expression
149      * \param a_stride optional Stride object, passing the strides.
150      */
151    inline Map(PointerArgType dataPtr, Index a_size, const StrideType& a_stride = StrideType())
152      : Base(cast_to_pointer_type(dataPtr), a_size), m_stride(a_stride)
153    {
154      PlainObjectType::Base::_check_template_params();
155    }
156
157    /** Constructor in the dynamic-size matrix case.
158      *
159      * \param dataPtr pointer to the array to map
160      * \param nbRows the number of rows of the matrix expression
161      * \param nbCols the number of columns of the matrix expression
162      * \param a_stride optional Stride object, passing the strides.
163      */
164    inline Map(PointerArgType dataPtr, Index nbRows, Index nbCols, const StrideType& a_stride = StrideType())
165      : Base(cast_to_pointer_type(dataPtr), nbRows, nbCols), m_stride(a_stride)
166    {
167      PlainObjectType::Base::_check_template_params();
168    }
169
170    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Map)
171
172  protected:
173    StrideType m_stride;
174};
175
176template<typename _Scalar, int _Rows, int _Cols, int _Options, int _MaxRows, int _MaxCols>
177inline Array<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>
178  ::Array(const Scalar *data)
179{
180  this->_set_noalias(Eigen::Map<const Array>(data));
181}
182
183template<typename _Scalar, int _Rows, int _Cols, int _Options, int _MaxRows, int _MaxCols>
184inline Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>
185  ::Matrix(const Scalar *data)
186{
187  this->_set_noalias(Eigen::Map<const Matrix>(data));
188}
189
190} // end namespace Eigen
191
192#endif // EIGEN_MAP_H
193