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/*=========================================================================
*
* Copyright NumFOCUS
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#ifndef itkOffset_h
#define itkOffset_h
#include "itkSize.h"
#include "itkMath.h"
#include <cstddef> // For ptrdiff_t.
namespace itk
{
/**
* \struct Offset
* \brief Represent a n-dimensional offset between two n-dimensional indexes of n-dimensional image.
*
* Offset is a templated class to represent a multi-dimensional offset,
* i.e. (i,j,k,...). Offset is templated over the dimension of the space.
* ITK assumes the first element of a size (bounds) is the fastest moving index.
*
* For efficiency, Offset does not define a default constructor, a
* copy constructor, or an operator=. We rely on the compiler to provide
* efficient bitwise copies.
*
* Offset is an "aggregate" class. Its data is public (m_InternalArray)
* allowing for fast and convenient instantiations/assignments.
*
* The following syntax for assigning an aggregate type like this is allowed/suggested:
*
*
* Offset<3> var{{ 256, 256, 20 }}; // Also prevent narrowing conversions
* Offset<3> var = {{ 256, 256, 20 }};
*
* The doubled braces {{ and }} are required to prevent `gcc -Wall'
* (and perhaps other compilers) from complaining about a partly
* bracketed initializer.
*
* As an aggregate type that is intended to provide highest performance
* characteristics, this class is not appropriate to inherit from,
* so setting this struct as final.
*
* \sa Index
* \ingroup ImageAccess
* \ingroup ITKCommon
*
* \sphinx
* \sphinxexample{Core/Common/AddOffsetToIndex,Add Offset To Index}
* \endsphinx
*/
template <unsigned int VDimension = 2>
struct ITK_TEMPLATE_EXPORT Offset final
{
public:
// Using the `rule of zero` to this aggregate type
// C++20 changes the definition of aggregate such that classes with any user-declared ctors are no longer aggregates.
/** Standard class type aliases. */
using Self = Offset;
/** Compatible Offset and value type alias. */
using OffsetType = Offset<VDimension>;
using OffsetValueType = itk::OffsetValueType;
/** Dimension constant */
static constexpr unsigned int Dimension = VDimension;
/** Get the dimension (size) of the index. */
static constexpr unsigned int
GetOffsetDimension()
{
return VDimension;
}
/** Add two offsets. */
const Self
operator+(const Self & vec) const
{
Self result;
for (unsigned int i = 0; i < VDimension; ++i)
{
result[i] = m_InternalArray[i] + vec.m_InternalArray[i];
}
return result;
}
/** Add a size to an offset. */
const Self
operator+(const Size<VDimension> & sz) const
{
Self result;
for (unsigned int i = 0; i < VDimension; ++i)
{
result[i] = m_InternalArray[i] + sz[i];
}
return result;
}
/** Increment index by a size. */
const Self &
operator+=(const Size<VDimension> & sz)
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_InternalArray[i] += sz[i];
}
return *this;
}
/** Decrement index by a size. */
const Self &
operator-=(const Size<VDimension> & sz)
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_InternalArray[i] -= sz[i];
}
return *this;
}
/** Subtract two offsets. */
const Self
operator-(const Self & vec) const
{
Self result;
for (unsigned int i = 0; i < VDimension; ++i)
{
result[i] = m_InternalArray[i] - vec.m_InternalArray[i];
}
return result;
}
/** Increment offset by an offset. */
const Self &
operator+=(const Self & vec)
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_InternalArray[i] += vec.m_InternalArray[i];
}
return *this;
}
/** Decrement offset by an offset. */
const Self &
operator-=(const Self & vec)
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_InternalArray[i] -= vec.m_InternalArray[i];
}
return *this;
}
/** Get the offset. This provides a read only pointer to the offset.
* \sa SetOffset() */
const OffsetValueType *
GetOffset() const
{
return m_InternalArray;
}
/** Set the index.
* Try to prototype this function so that val has to point to a block of
* memory that is the appropriate size.
* \sa GetOffset() */
void
SetOffset(const OffsetValueType val[VDimension])
{
std::copy_n(val, VDimension, m_InternalArray);
}
/** Sets the value of one of the elements.
* This method is mainly intended to facilitate the access to elements
* from Tcl and Python where C++ notation is not very convenient.
* \warning No bound checking is performed.
* \sa SetIndex()
* \sa GetElement() */
void
SetElement(unsigned long element, OffsetValueType val)
{
m_InternalArray[element] = val;
}
/** Gets the value of one of the elements.
* This method is mainly intended to facilitate the access to elements
* from Tcl and Python where C++ notation is not very convenient.
* \warning No bound checking is performed
* \sa GetIndex()
* \sa SetElement() */
OffsetValueType
GetElement(unsigned long element) const
{
return m_InternalArray[element];
}
/** Set one value for the offset in all dimensions. Useful for initializing
* an offset to zero. */
void
Fill(OffsetValueType value)
{
std::fill_n(begin(), size(), value);
} // MATCH std::array assign, ITK Fill
/** Offset is an "aggregate" class. Its data is public (m_InternalArray)
* allowing for fast and convenient instantiations/assignments.
* ( See main class documentation for an example of initialization)
*/
/*
* Ask the compiler to align a type to the maximum useful alignment for the target
* machine you are compiling for. Whenever you leave out the alignment factor in an
* aligned attribute specification, the compiler automatically sets the alignment
* for the type to the largest alignment that is ever used for any data type on
* the target machine you are compiling for. Doing this can often make copy
* operations more efficient, because the compiler can use whatever instructions
* copy the biggest chunks of memory when performing copies to or from the variables
* that have types that you have aligned this way.
*/
static_assert(VDimension > 0, "Error: Only positive value sized VDimension allowed");
alignas(OffsetValueType) OffsetValueType m_InternalArray[VDimension];
/** Copy values from a FixedArray by rounding each one of the components */
template <typename TCoordRep>
inline void
CopyWithRound(const FixedArray<TCoordRep, VDimension> & point)
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_InternalArray[i] = Math::Round<OffsetValueType>(point[i]);
}
}
/** Copy values from a FixedArray by casting each one of the components */
template <typename TCoordRep>
inline void
CopyWithCast(const FixedArray<TCoordRep, VDimension> & point)
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_InternalArray[i] = static_cast<OffsetValueType>(point[i]);
}
}
/** Return a basis vector of the form [0, ..., 0, 1, 0, ... 0] where the "1"
* is positioned in the location specified by the parameter "dim". Valid
* values of "dim" are 0, ..., VDimension-1. */
static Self
GetBasisOffset(unsigned int dim);
// ======================= Mirror the access pattern behavior of the std::array class
/**
* Mirror the std::array type aliases and member function
* so that the Offset class can be treated as a container
* class in a way that is similar to the std::array.
*/
using value_type = itk::OffsetValueType;
using reference = value_type &;
using const_reference = const value_type &;
using iterator = value_type *;
using const_iterator = const value_type *;
using size_type = unsigned int;
using difference_type = ptrdiff_t;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
/**
* Mirror behavior of the std::array manipulations
* See std::array for documentation on these methods
*/
void
assign(const value_type & newValue)
{
std::fill_n(begin(), size(), newValue);
}
void
swap(Offset & other)
{
std::swap(m_InternalArray, other.m_InternalArray);
}
constexpr const_iterator
cbegin() const
{
return &m_InternalArray[0];
}
constexpr iterator
begin()
{
return &m_InternalArray[0];
}
constexpr const_iterator
begin() const
{
return &m_InternalArray[0];
}
constexpr const_iterator
cend() const
{
return &m_InternalArray[VDimension];
}
constexpr iterator
end()
{
return &m_InternalArray[VDimension];
}
constexpr const_iterator
end() const
{
return &m_InternalArray[VDimension];
}
reverse_iterator
rbegin()
{
return reverse_iterator(end());
}
const_reverse_iterator
rbegin() const
{
return const_reverse_iterator(end());
}
reverse_iterator
rend()
{
return reverse_iterator(begin());
}
const_reverse_iterator
rend() const
{
return const_reverse_iterator(begin());
}
constexpr size_type
size() const
{
return VDimension;
}
constexpr size_type
max_size() const
{
return VDimension;
}
constexpr bool
empty() const
{
return false;
}
reference operator[](size_type pos) { return m_InternalArray[pos]; }
const_reference operator[](size_type pos) const { return m_InternalArray[pos]; }
reference
at(size_type pos)
{
ExceptionThrowingBoundsCheck(pos);
return m_InternalArray[pos];
}
const_reference
at(size_type pos) const
{
ExceptionThrowingBoundsCheck(pos);
return m_InternalArray[pos];
}
reference
front()
{
return *begin();
}
const_reference
front() const
{
return *begin();
}
reference
back()
{
return VDimension ? *(end() - 1) : *end();
}
const_reference
back() const
{
return VDimension ? *(end() - 1) : *end();
}
OffsetValueType *
data()
{
return &m_InternalArray[0];
}
const OffsetValueType *
data() const
{
return &m_InternalArray[0];
}
private:
void
ExceptionThrowingBoundsCheck(size_type pos) const
{
if (pos >= VDimension)
{
throw std::out_of_range("array::ExceptionThrowingBoundsCheck");
}
}
}; //------------ End struct Offset
template <unsigned int VDimension>
Offset<VDimension>
Offset<VDimension>::GetBasisOffset(unsigned int dim)
{
Self ind;
memset(ind.m_InternalArray, 0, sizeof(OffsetValueType) * VDimension);
ind.m_InternalArray[dim] = 1;
return ind;
}
template <unsigned int VDimension>
std::ostream &
operator<<(std::ostream & os, const Offset<VDimension> & ind)
{
os << '[';
unsigned int dimlim = VDimension - 1;
for (unsigned int i = 0; i < dimlim; ++i)
{
os << ind[i] << ", ";
}
if (VDimension >= 1)
{
os << ind[VDimension - 1];
}
os << ']';
return os;
}
// ======================= Mirror the access pattern behavior of the std::array class
// Array comparisons.
template <unsigned int VDimension>
inline bool
operator==(const Offset<VDimension> & one, const Offset<VDimension> & two)
{
return std::equal(one.begin(), one.end(), two.begin());
}
template <unsigned int VDimension>
inline bool
operator!=(const Offset<VDimension> & one, const Offset<VDimension> & two)
{
return !(one == two);
}
template <unsigned int VDimension>
inline bool
operator<(const Offset<VDimension> & one, const Offset<VDimension> & two)
{
return std::lexicographical_compare(one.begin(), one.end(), two.begin(), two.end());
}
template <unsigned int VDimension>
inline bool
operator>(const Offset<VDimension> & one, const Offset<VDimension> & two)
{
return two < one;
}
template <unsigned int VDimension>
inline bool
operator<=(const Offset<VDimension> & one, const Offset<VDimension> & two)
{
return !(one > two);
}
template <unsigned int VDimension>
inline bool
operator>=(const Offset<VDimension> & one, const Offset<VDimension> & two)
{
return !(one < two);
}
// Specialized algorithms [6.2.2.2].
template <unsigned int VDimension>
inline void
swap(Offset<VDimension> & one, Offset<VDimension> & two)
{
std::swap(one.m_InternalArray, two.m_InternalArray);
}
} // end namespace itk
#endif
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