/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date: 16/10/14 6:02p $Revision:  V.1.4.5
*
* Project:      CMSIS DSP Library
* Title:        arm_rfft_f32.c
*
* Description:  RFFT & RIFFT Floating point process function
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

extern void arm_radix4_butterfly_f32(
    float32_t * pSrc,
    uint16_t fftLen,
    float32_t * pCoef,
    uint16_t twidCoefModifier);

extern void arm_radix4_butterfly_inverse_f32(
    float32_t * pSrc,
    uint16_t fftLen,
    float32_t * pCoef,
    uint16_t twidCoefModifier,
    float32_t onebyfftLen);

extern void arm_bitreversal_f32(
    float32_t * pSrc,
    uint16_t fftSize,
    uint16_t bitRevFactor,
    uint16_t * pBitRevTab);

/**
 * @ingroup groupTransforms
 */

/*--------------------------------------------------------------------
 *      Internal functions prototypes
 *--------------------------------------------------------------------*/

void arm_split_rfft_f32(
    float32_t * pSrc,
    uint32_t fftLen,
    float32_t * pATable,
    float32_t * pBTable,
    float32_t * pDst,
    uint32_t modifier);
void arm_split_rifft_f32(
    float32_t * pSrc,
    uint32_t fftLen,
    float32_t * pATable,
    float32_t * pBTable,
    float32_t * pDst,
    uint32_t modifier);

/**
 * @addtogroup RealFFT
 * @{
 */

/**
 * @brief Processing function for the floating-point RFFT/RIFFT.
 * @deprecated Do not use this function.  It has been superceded by \ref arm_rfft_fast_f32 and will be removed
 * in the future.
 * @param[in]  *S    points to an instance of the floating-point RFFT/RIFFT structure.
 * @param[in]  *pSrc points to the input buffer.
 * @param[out] *pDst points to the output buffer.
 * @return none.
 */

void arm_rfft_f32(
    const arm_rfft_instance_f32 * S,
    float32_t * pSrc,
    float32_t * pDst)
{
    const arm_cfft_radix4_instance_f32 *S_CFFT = S->pCfft;


    /* Calculation of Real IFFT of input */
    if(S->ifftFlagR == 1u)
    {
        /*  Real IFFT core process */
        arm_split_rifft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal,
                            S->pTwiddleBReal, pDst, S->twidCoefRModifier);


        /* Complex radix-4 IFFT process */
        arm_radix4_butterfly_inverse_f32(pDst, S_CFFT->fftLen,
                                         S_CFFT->pTwiddle,
                                         S_CFFT->twidCoefModifier,
                                         S_CFFT->onebyfftLen);

        /* Bit reversal process */
        if(S->bitReverseFlagR == 1u)
        {
            arm_bitreversal_f32(pDst, S_CFFT->fftLen,
                                S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
        }
    }
    else
    {

        /* Calculation of RFFT of input */

        /* Complex radix-4 FFT process */
        arm_radix4_butterfly_f32(pSrc, S_CFFT->fftLen,
                                 S_CFFT->pTwiddle, S_CFFT->twidCoefModifier);

        /* Bit reversal process */
        if(S->bitReverseFlagR == 1u)
        {
            arm_bitreversal_f32(pSrc, S_CFFT->fftLen,
                                S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
        }


        /*  Real FFT core process */
        arm_split_rfft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal,
                           S->pTwiddleBReal, pDst, S->twidCoefRModifier);
    }

}

/**
   * @} end of RealFFT group
   */

/**
 * @brief  Core Real FFT process
 * @param[in]   *pSrc               points to the input buffer.
 * @param[in]   fftLen              length of FFT.
 * @param[in]   *pATable            points to the twiddle Coef A buffer.
 * @param[in]   *pBTable            points to the twiddle Coef B buffer.
 * @param[out]  *pDst               points to the output buffer.
 * @param[in]   modifier            twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
 * @return none.
 */

void arm_split_rfft_f32(
    float32_t * pSrc,
    uint32_t fftLen,
    float32_t * pATable,
    float32_t * pBTable,
    float32_t * pDst,
    uint32_t modifier)
{
    uint32_t i;                                    /* Loop Counter */
    float32_t outR, outI;                          /* Temporary variables for output */
    float32_t *pCoefA, *pCoefB;                    /* Temporary pointers for twiddle factors */
    float32_t CoefA1, CoefA2, CoefB1;              /* Temporary variables for twiddle coefficients */
    float32_t *pDst1 = &pDst[2], *pDst2 = &pDst[(4u * fftLen) - 1u];      /* temp pointers for output buffer */
    float32_t *pSrc1 = &pSrc[2], *pSrc2 = &pSrc[(2u * fftLen) - 1u];      /* temp pointers for input buffer */

    /* Init coefficient pointers */
    pCoefA = &pATable[modifier * 2u];
    pCoefB = &pBTable[modifier * 2u];

    i = fftLen - 1u;

    while(i > 0u)
    {
        /*
           outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]
           + pSrc[2 * n - 2 * i] * pBTable[2 * i] +
           pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
         */

        /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +
           pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
           pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */

        /* read pATable[2 * i] */
        CoefA1 = *pCoefA++;
        /* pATable[2 * i + 1] */
        CoefA2 = *pCoefA;

        /* pSrc[2 * i] * pATable[2 * i] */
        outR = *pSrc1 * CoefA1;
        /* pSrc[2 * i] * CoefA2 */
        outI = *pSrc1++ * CoefA2;

        /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
        outR -= (*pSrc1 + *pSrc2) * CoefA2;
        /* pSrc[2 * i + 1] * CoefA1 */
        outI += *pSrc1++ * CoefA1;

        CoefB1 = *pCoefB;

        /* pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
        outI -= *pSrc2-- * CoefB1;
        /* pSrc[2 * fftLen - 2 * i] * CoefA2 */
        outI -= *pSrc2 * CoefA2;

        /* pSrc[2 * fftLen - 2 * i] * CoefB1 */
        outR += *pSrc2-- * CoefB1;

        /* write output */
        *pDst1++ = outR;
        *pDst1++ = outI;

        /* write complex conjugate output */
        *pDst2-- = -outI;
        *pDst2-- = outR;

        /* update coefficient pointer */
        pCoefB = pCoefB + (modifier * 2u);
        pCoefA = pCoefA + ((modifier * 2u) - 1u);

        i--;

    }

    pDst[2u * fftLen] = pSrc[0] - pSrc[1];
    pDst[(2u * fftLen) + 1u] = 0.0f;

    pDst[0] = pSrc[0] + pSrc[1];
    pDst[1] = 0.0f;

}


/**
 * @brief  Core Real IFFT process
 * @param[in]   *pSrc               points to the input buffer.
 * @param[in]   fftLen              length of FFT.
 * @param[in]   *pATable            points to the twiddle Coef A buffer.
 * @param[in]   *pBTable            points to the twiddle Coef B buffer.
 * @param[out]  *pDst               points to the output buffer.
 * @param[in]   modifier            twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
 * @return none.
 */

void arm_split_rifft_f32(
    float32_t * pSrc,
    uint32_t fftLen,
    float32_t * pATable,
    float32_t * pBTable,
    float32_t * pDst,
    uint32_t modifier)
{
    float32_t outR, outI;                          /* Temporary variables for output */
    float32_t *pCoefA, *pCoefB;                    /* Temporary pointers for twiddle factors */
    float32_t CoefA1, CoefA2, CoefB1;              /* Temporary variables for twiddle coefficients */
    float32_t *pSrc1 = &pSrc[0], *pSrc2 = &pSrc[(2u * fftLen) + 1u];

    pCoefA = &pATable[0];
    pCoefB = &pBTable[0];

    while(fftLen > 0u)
    {
        /*
           outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
           pIn[2 * n - 2 * i] * pBTable[2 * i] -
           pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);

           outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -
           pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
           pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);

         */

        CoefA1 = *pCoefA++;
        CoefA2 = *pCoefA;

        /* outR = (pSrc[2 * i] * CoefA1 */
        outR = *pSrc1 * CoefA1;

        /* - pSrc[2 * i] * CoefA2 */
        outI = -(*pSrc1++) * CoefA2;

        /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
        outR += (*pSrc1 + *pSrc2) * CoefA2;

        /* pSrc[2 * i + 1] * CoefA1 */
        outI += (*pSrc1++) * CoefA1;

        CoefB1 = *pCoefB;

        /* - pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
        outI -= *pSrc2-- * CoefB1;

        /* pSrc[2 * fftLen - 2 * i] * CoefB1 */
        outR += *pSrc2 * CoefB1;

        /* pSrc[2 * fftLen - 2 * i] * CoefA2 */
        outI += *pSrc2-- * CoefA2;

        /* write output */
        *pDst++ = outR;
        *pDst++ = outI;

        /* update coefficient pointer */
        pCoefB = pCoefB + (modifier * 2u);
        pCoefA = pCoefA + ((modifier * 2u) - 1u);

        /* Decrement loop count */
        fftLen--;
    }

}
