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/* ----------------------------------------------------------------------    

* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    

*    

* $Date:        19. March 2015

* $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--;

  }

}