vnl_fft_prime_factors.h

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#ifndef vnl_fft_prime_factors_h_
#define vnl_fft_prime_factors_h_

//:
// \file 
// \author Veit U.B. Schenk, Oxford RRG, 19 Mar 98
// Modifications
// \verbatim
// 10/4/2001 Ian Scott (Manchester) Coverted perceps header to doxygen
// \endverbatim


#include <vnl/algo/vnl_fft.h>

//: Holds prime factor information .
// Helper class  used by the vnl_fft_xd<> FFT routines
//
// Given an integer N of the form
//   N = (2**P)(3**Q)(5**R)
// split N into its primefactors (2, 3, 5)
export template <class T>
struct vnl_fft_prime_factors
{
  vnl_fft_prime_factors();

  //: constructor takes the size of the signal.
  vnl_fft_prime_factors(int N) { construct(N); }

  ~vnl_fft_prime_factors () { destruct(); }

  //: array of twiddle factors.
  T const *trigs () const { return trigs_; }

  //: number which was factorized
  int number () const { return number_; }

  //: exponents P, Q, R.
  int const *pqr () const { return pqr_; }

  operator bool () const { return trigs_ && info_ >= 0; }

  void resize(int N) {
    destruct();
    construct(N);
  }

private:
  T *trigs_;
  int number_;   // the number that is being split into prime-facs
  int pqr_[3];   // store P, Q and R
  int info_;

  void construct(int N);
  void destruct();

  // disallow copying
  vnl_fft_prime_factors (vnl_fft_prime_factors<T> const &) { }
  void operator= (vnl_fft_prime_factors<T> const &) { }
};

#endif // vnl_fft_prime_factors_h_

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