#ifndef __FFT_H__ /*============================================================================= | | NAME | | FFT.h | | DESCRIPTION | | This program does an in-place one dimensional complex discrete | Fourier transform. It uses an FFT algorithm for a number of | input points which is a power of two. | | AUTHOR | | Sean O'Connor 19 November 2005 | | LEGAL | | FFT Version 1.2 - An FFT utility library in C++. | Copyright (C) 2005-2017 by Sean Erik O'Connor. All Rights Reserved. | | This program is free software: you can redistribute it and/or modify | it under the terms of the GNU General Public License as published by | the Free Software Foundation, either version 3 of the License, or | (at your option) any later version. | | This program is distributed in the hope that it will be useful, | but WITHOUT ANY WARRANTY; without even the implied warranty of | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | GNU General Public License for more details. | | You should have received a copy of the GNU General Public License | along with this program. If not, see <http://www.gnu.org/licenses/>. | | The author's address is artificer!AT!seanerikoconnor!DOT!freeservers!DOT!com | with !DOT! replaced by . and the !AT! replaced by @ | +============================================================================*/ /* * We must set the size of the sine and cosine table used in the FFT. * The table is called starting_multiplier. * * Suppose MAX is the largest number of points we would ever transform. We set * * MAX_TABLE_SIZE = LOG ( MAX ) - 1 * 2 * * to be the size of the table. This table can now be used by the FFT for * any number of points from 2 up to MAX. * * For example, if MAX_TABLE_SIZE = 14, then we can transform anywhere from * 2 to 2 ^ 15 = 32,768 points, using the same sine and cosine table. * */ const int MAX_TABLE_SIZE = 13 ; // Derive the FFT class from an STL vector of double precision types. // Thus we get the vector's data manipulation attributes and // we can substitute FFT objects into an existing software // framework which uses vector objects in containers. // But extend the class by adding a Fourier Transform capability. // class FastFourierTransform : public vector< complex<double> > // Need spaces between angle brackets to satisfy compiler. { public: // Default constructor. FastFourierTransform() ; // Destructor. ~FastFourierTransform() ; // Copy constructor ; FastFourierTransform( const FastFourierTransform & transform ) ; // Assignment operator. FastFourierTransform & operator=( const FastFourierTransform & transform ) ; // Fast Fourier transform capability. void fft( bool direction = true ) ; // Maybe these should be private to be safe! protected: bool direction ; private: // Table of sines and cosines whose values are created the first // time any object calls the fft() member function and which are // shared among all subsequent objects. static complex<double> starting_multiplier[ MAX_TABLE_SIZE ] ; static bool called_already ; static const double PI ; // Helper function used by FFT member function only. static int reverse_bits( int n, int num_bits ) ; } ; /*============================================================================= | | NAME | | FastFourierTransformException | | DESCRIPTION | | Helper class for recording data thrown by FastFourierTransform. | | BUGS | +============================================================================*/ class FastFourierTransformException : public runtime_error { public: // This form will be used most often in a throw. FastFourierTransformException( const string & description ) : runtime_error( description ) { } ; // Throw with no error message. FastFourierTransformException() : runtime_error( "FFT exception: " ) { } ; } ; // end class FastFourierTransformException #endif // __FFT_H__