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ArrayNDScanner.hh
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ArrayNDScanner.hh
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#ifndef NPSTAT_ARRAYNDSCANNER_HH_
#define NPSTAT_ARRAYNDSCANNER_HH_
/*!
// \file ArrayNDScanner.hh
//
// \brief Iteration over indices of a multidimensional array
//
// Author: I. Volobouev
//
// July 2012
*/
#include <vector>
#include <climits>
namespace npstat {
/**
* This class can be used to iterate over array indices without actually
* building the array or requesting any memory from the heap. Typical use:
*
* @code
* for (ArrayNDScanner scanner(shape); scanner.isValid(); ++scanner)
* {
* scanner.getIndex(indexArray, indexArrayLen);
* .... Do what is necessary with multidimensional index ....
* .... Extract linear index: ...............................
* scanner.state();
* }
* @endcode
*
* This can be useful, for example, in case one needs to iterate over
* slices of some array (so that the array itself can not be used
* to obtain similar information easily).
*/
class ArrayNDScanner
{
public:
//@{
/** Constructor from a multidimensional array shape */
inline ArrayNDScanner(const unsigned* shape, const unsigned lenShape)
{initialize(shape, lenShape);}
inline ArrayNDScanner(const std::vector<unsigned>& shape)
{initialize(shape.empty() ? static_cast<unsigned*>(0) :
&shape[0], shape.size());}
//@}
/** Dimensionality of the scan */
inline unsigned dim() const {return dim_;}
/** Retrieve current state (i.e., linear index of the scan) */
inline unsigned long state() const {return state_;}
/** Maximum possible state (i.e., linear index of the scan) */
inline unsigned long maxState() const {return maxState_;}
/** Returns false when iteration is complete */
inline bool isValid() const {return state_ < maxState_;}
/** Retrieve current multidimensional index */
void getIndex(unsigned* index, unsigned indexBufferLen) const;
/** Reset the state (as if the object has just been constructed) */
inline void reset() {state_ = 0UL;}
/** Prefix increment */
inline ArrayNDScanner& operator++()
{if (state_ < maxState_) ++state_; return *this;}
/** Postfix increment (distinguished by the dummy "int" parameter) */
inline void operator++(int) {if (state_ < maxState_) ++state_;}
/** Set the state directly */
inline void setState(const unsigned long state)
{state_ = state <= maxState_ ? state : maxState_;}
private:
ArrayNDScanner();
void initialize(const unsigned* shape, unsigned lenShape);
unsigned long strides_[CHAR_BIT*sizeof(unsigned long)];
unsigned long state_;
unsigned long maxState_;
unsigned dim_;
};
}
#endif // NPSTAT_ARRAYSCANNER_HH_

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