/*

 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.sun.media.sound;

/**

 * Fast Fourier Transformer.

 *

 * @author Karl Helgason

 */

public final class FFT {

    private double[] w;

    private int fftFrameSize;

    private int sign;

    private int[] bitm_array;

    private int fftFrameSize2;

    // Sign = -1 is FFT, 1 is IFFT (inverse FFT)

    // Data = Interlaced double array to be transformed.

    // The order is: real (sin), complex (cos)

    // Framesize must be power of 2

    public FFT(int fftFrameSize, int sign) {

        w = computeTwiddleFactors(fftFrameSize, sign);

        this.fftFrameSize = fftFrameSize;

        this.sign = sign;

        fftFrameSize2 = fftFrameSize << 1;

        // Pre-process Bit-Reversal

        bitm_array = new int[fftFrameSize2];

        for (int i = 2; i < fftFrameSize2; i += 2) {

            int j;

            int bitm;

            for (bitm = 2, j = 0; bitm < fftFrameSize2; bitm <<= 1) {

                if ((i & bitm) != 0)

                    j++;

                j <<= 1;

            }

            bitm_array[i] = j;

        }

    }

    public void transform(double[] data) {

        bitreversal(data);

        calc(fftFrameSize, data, sign, w);

    }

    private final static double[] computeTwiddleFactors(int fftFrameSize,

            int sign) {

        int imax = (int) (Math.log(fftFrameSize) / Math.log(2.));

        double[] warray = new double[(fftFrameSize - 1) * 4];

        int w_index = 0;

        for (int i = 0,  nstep = 2; i < imax; i++) {

            int jmax = nstep;

            nstep <<= 1;

            double wr = 1.0;

            double wi = 0.0;

            double arg = Math.PI / (jmax >> 1);

            double wfr = Math.cos(arg);

            double wfi = sign * Math.sin(arg);

            for (int j = 0; j < jmax; j += 2) {

                warray[w_index++] = wr;

                warray[w_index++] = wi;

                double tempr = wr;

                wr = tempr * wfr - wi * wfi;

                wi = tempr * wfi + wi * wfr;

            }

        }

        // PRECOMPUTATION of wwr1, wwi1 for factor 4 Decomposition (3 * complex

        // operators and 8 +/- complex operators)

        {

            w_index = 0;

            int w_index2 = warray.length >> 1;

            for (int i = 0,  nstep = 2; i < (imax - 1); i++) {

                int jmax = nstep;

                nstep *= 2;

                int ii = w_index + jmax;

                for (int j = 0; j < jmax; j += 2) {

                    double wr = warray[w_index++];

                    double wi = warray[w_index++];

                    double wr1 = warray[ii++];

                    double wi1 = warray[ii++];

                    warray[w_index2++] = wr * wr1 - wi * wi1;

                    warray[w_index2++] = wr * wi1 + wi * wr1;

                }

            }

        }

        return warray;

    }

    private final static void calc(int fftFrameSize, double[] data, int sign,

            double[] w) {

        final int fftFrameSize2 = fftFrameSize << 1;

        int nstep = 2;

        if (nstep >= fftFrameSize2)

            return;

        int i = nstep - 2;

        if (sign == -1)

            calcF4F(fftFrameSize, data, i, nstep, w);

        else

            calcF4I(fftFrameSize, data, i, nstep, w);

    }

    private final static void calcF2E(int fftFrameSize, double[] data, int i,

            int nstep, double[] w) {

        int jmax = nstep;

        for (int n = 0; n < jmax; n += 2) {

            double wr = w[i++];

            double wi = w[i++];

            int m = n + jmax;

            double datam_r = data[m];

            double datam_i = data[m + 1];

            double datan_r = data[n];

            double datan_i = data[n + 1];

            double tempr = datam_r * wr - datam_i * wi;

            double tempi = datam_r * wi + datam_i * wr;

            data[m] = datan_r - tempr;

            data[m + 1] = datan_i - tempi;

            data[n] = datan_r + tempr;

            data[n + 1] = datan_i + tempi;

        }

        return;

    }

    // Perform Factor-4 Decomposition with 3 * complex operators and 8 +/-

    // complex operators

    private final static void calcF4F(int fftFrameSize, double[] data, int i,

            int nstep, double[] w) {

        final int fftFrameSize2 = fftFrameSize << 1; // 2*fftFrameSize;

        // Factor-4 Decomposition

        int w_len = w.length >> 1;

        while (nstep < fftFrameSize2) {

            if (nstep << 2 == fftFrameSize2) {

                // Goto Factor-4 Final Decomposition

                // calcF4E(data, i, nstep, -1, w);

                calcF4FE(fftFrameSize, data, i, nstep, w);

                return;

            }

            int jmax = nstep;

            int nnstep = nstep << 1;

            if (nnstep == fftFrameSize2) {

                // Factor-4 Decomposition not possible

                calcF2E(fftFrameSize, data, i, nstep, w);

                return;

            }

            nstep <<= 2;

            int ii = i + jmax;

            int iii = i + w_len;

            {

                i += 2;

                ii += 2;

                iii += 2;

                for (int n = 0; n < fftFrameSize2; n += nstep) {

                    int m = n + jmax;

                    double datam1_r = data[m];

                    double datam1_i = data[m + 1];

                    double datan1_r = data[n];

                    double datan1_i = data[n + 1];

                    n += nnstep;

                    m += nnstep;

                    double datam2_r = data[m];

                    double datam2_i = data[m + 1];

                    double datan2_r = data[n];

                    double datan2_i = data[n + 1];

                    double tempr = datam1_r;

                    double tempi = datam1_i;

                    datam1_r = datan1_r - tempr;

                    datam1_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    double n2w1r = datan2_r;

                    double n2w1i = datan2_i;

                    double m2ww1r = datam2_r;

                    double m2ww1i = datam2_i;

                    tempr = m2ww1r - n2w1r;

                    tempi = m2ww1i - n2w1i;

                    datam2_r = datam1_r + tempi;

                    datam2_i = datam1_i - tempr;

                    datam1_r = datam1_r - tempi;

                    datam1_i = datam1_i + tempr;

                    tempr = n2w1r + m2ww1r;

                    tempi = n2w1i + m2ww1i;

                    datan2_r = datan1_r - tempr;

                    datan2_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    data[m] = datam2_r;

                    data[m + 1] = datam2_i;

                    data[n] = datan2_r;

                    data[n + 1] = datan2_i;

                    n -= nnstep;

                    m -= nnstep;

                    data[m] = datam1_r;

                    data[m + 1] = datam1_i;

                    data[n] = datan1_r;

                    data[n + 1] = datan1_i;

                }

            }

            for (int j = 2; j < jmax; j += 2) {

                double wr = w[i++];

                double wi = w[i++];

                double wr1 = w[ii++];

                double wi1 = w[ii++];

                double wwr1 = w[iii++];

                double wwi1 = w[iii++];

                // double wwr1 = wr * wr1 - wi * wi1; // these numbers can be

                // precomputed!!!

                // double wwi1 = wr * wi1 + wi * wr1;

                for (int n = j; n < fftFrameSize2; n += nstep) {

                    int m = n + jmax;

                    double datam1_r = data[m];

                    double datam1_i = data[m + 1];

                    double datan1_r = data[n];

                    double datan1_i = data[n + 1];

                    n += nnstep;

                    m += nnstep;

                    double datam2_r = data[m];

                    double datam2_i = data[m + 1];

                    double datan2_r = data[n];

                    double datan2_i = data[n + 1];

                    double tempr = datam1_r * wr - datam1_i * wi;

                    double tempi = datam1_r * wi + datam1_i * wr;

                    datam1_r = datan1_r - tempr;

                    datam1_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    double n2w1r = datan2_r * wr1 - datan2_i * wi1;

                    double n2w1i = datan2_r * wi1 + datan2_i * wr1;

                    double m2ww1r = datam2_r * wwr1 - datam2_i * wwi1;

                    double m2ww1i = datam2_r * wwi1 + datam2_i * wwr1;

                    tempr = m2ww1r - n2w1r;

                    tempi = m2ww1i - n2w1i;

                    datam2_r = datam1_r + tempi;

                    datam2_i = datam1_i - tempr;

                    datam1_r = datam1_r - tempi;

                    datam1_i = datam1_i + tempr;

                    tempr = n2w1r + m2ww1r;

                    tempi = n2w1i + m2ww1i;

                    datan2_r = datan1_r - tempr;

                    datan2_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    data[m] = datam2_r;

                    data[m + 1] = datam2_i;

                    data[n] = datan2_r;

                    data[n + 1] = datan2_i;

                    n -= nnstep;

                    m -= nnstep;

                    data[m] = datam1_r;

                    data[m + 1] = datam1_i;

                    data[n] = datan1_r;

                    data[n + 1] = datan1_i;

                }

            }

            i += jmax << 1;

        }

        calcF2E(fftFrameSize, data, i, nstep, w);

    }

    // Perform Factor-4 Decomposition with 3 * complex operators and 8 +/-

    // complex operators

    private final static void calcF4I(int fftFrameSize, double[] data, int i,

            int nstep, double[] w) {

        final int fftFrameSize2 = fftFrameSize << 1; // 2*fftFrameSize;

        // Factor-4 Decomposition

        int w_len = w.length >> 1;

        while (nstep < fftFrameSize2) {

            if (nstep << 2 == fftFrameSize2) {

                // Goto Factor-4 Final Decomposition

                // calcF4E(data, i, nstep, 1, w);

                calcF4IE(fftFrameSize, data, i, nstep, w);

                return;

            }

            int jmax = nstep;

            int nnstep = nstep << 1;

            if (nnstep == fftFrameSize2) {

                // Factor-4 Decomposition not possible

                calcF2E(fftFrameSize, data, i, nstep, w);

                return;

            }

            nstep <<= 2;

            int ii = i + jmax;

            int iii = i + w_len;

            {

                i += 2;

                ii += 2;

                iii += 2;

                for (int n = 0; n < fftFrameSize2; n += nstep) {

                    int m = n + jmax;

                    double datam1_r = data[m];

                    double datam1_i = data[m + 1];

                    double datan1_r = data[n];

                    double datan1_i = data[n + 1];

                    n += nnstep;

                    m += nnstep;

                    double datam2_r = data[m];

                    double datam2_i = data[m + 1];

                    double datan2_r = data[n];

                    double datan2_i = data[n + 1];

                    double tempr = datam1_r;

                    double tempi = datam1_i;

                    datam1_r = datan1_r - tempr;

                    datam1_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    double n2w1r = datan2_r;

                    double n2w1i = datan2_i;

                    double m2ww1r = datam2_r;

                    double m2ww1i = datam2_i;

                    tempr = n2w1r - m2ww1r;

                    tempi = n2w1i - m2ww1i;

                    datam2_r = datam1_r + tempi;

                    datam2_i = datam1_i - tempr;

                    datam1_r = datam1_r - tempi;

                    datam1_i = datam1_i + tempr;

                    tempr = n2w1r + m2ww1r;

                    tempi = n2w1i + m2ww1i;

                    datan2_r = datan1_r - tempr;

                    datan2_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    data[m] = datam2_r;

                    data[m + 1] = datam2_i;

                    data[n] = datan2_r;

                    data[n + 1] = datan2_i;

                    n -= nnstep;

                    m -= nnstep;

                    data[m] = datam1_r;

                    data[m + 1] = datam1_i;

                    data[n] = datan1_r;

                    data[n + 1] = datan1_i;

                }

            }

            for (int j = 2; j < jmax; j += 2) {

                double wr = w[i++];

                double wi = w[i++];

                double wr1 = w[ii++];

                double wi1 = w[ii++];

                double wwr1 = w[iii++];

                double wwi1 = w[iii++];

                // double wwr1 = wr * wr1 - wi * wi1; // these numbers can be

                // precomputed!!!

                // double wwi1 = wr * wi1 + wi * wr1;

                for (int n = j; n < fftFrameSize2; n += nstep) {

                    int m = n + jmax;

                    double datam1_r = data[m];

                    double datam1_i = data[m + 1];

                    double datan1_r = data[n];

                    double datan1_i = data[n + 1];

                    n += nnstep;

                    m += nnstep;

                    double datam2_r = data[m];

                    double datam2_i = data[m + 1];

                    double datan2_r = data[n];

                    double datan2_i = data[n + 1];

                    double tempr = datam1_r * wr - datam1_i * wi;

                    double tempi = datam1_r * wi + datam1_i * wr;

                    datam1_r = datan1_r - tempr;

                    datam1_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    double n2w1r = datan2_r * wr1 - datan2_i * wi1;

                    double n2w1i = datan2_r * wi1 + datan2_i * wr1;

                    double m2ww1r = datam2_r * wwr1 - datam2_i * wwi1;

                    double m2ww1i = datam2_r * wwi1 + datam2_i * wwr1;

                    tempr = n2w1r - m2ww1r;

                    tempi = n2w1i - m2ww1i;

                    datam2_r = datam1_r + tempi;

                    datam2_i = datam1_i - tempr;

                    datam1_r = datam1_r - tempi;

                    datam1_i = datam1_i + tempr;

                    tempr = n2w1r + m2ww1r;

                    tempi = n2w1i + m2ww1i;

                    datan2_r = datan1_r - tempr;

                    datan2_i = datan1_i - tempi;

                    datan1_r = datan1_r + tempr;

                    datan1_i = datan1_i + tempi;

                    data[m] = datam2_r;

                    data[m + 1] = datam2_i;

                    data[n] = datan2_r;

                    data[n + 1] = datan2_i;

                    n -= nnstep;

                    m -= nnstep;

                    data[m] = datam1_r;

                    data[m + 1] = datam1_i;

                    data[n] = datan1_r;

                    data[n + 1] = datan1_i;

                }

            }

            i += jmax << 1;

        }

        calcF2E(fftFrameSize, data, i, nstep, w);

    }

    // Perform Factor-4 Decomposition with 3 * complex operators and 8 +/-

    // complex operators

    private final static void calcF4FE(int fftFrameSize, double[] data, int i,

            int nstep, double[] w) {

        final int fftFrameSize2 = fftFrameSize << 1; // 2*fftFrameSize;

        // Factor-4 Decomposition

        int w_len = w.length >> 1;

        while (nstep < fftFrameSize2) {

            int jmax = nstep;

            int nnstep = nstep << 1;

            if (nnstep == fftFrameSize2) {

                // Factor-4 Decomposition not possible

                calcF2E(fftFrameSize, data, i, nstep, w);

                return;

            }

            nstep <<= 2;

            int ii = i + jmax;

            int iii = i + w_len;

            for (int n = 0; n < jmax; n += 2) {

                double wr = w[i++];

                double wi = w[i++];

                double wr1 = w[ii++];

                double wi1 = w[ii++];

                double wwr1 = w[iii++];

                double wwi1 = w[iii++];

                // double wwr1 = wr * wr1 - wi * wi1; // these numbers can be

                // precomputed!!!