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

 * Project:      CMSIS DSP Library

 * Title:        arm_rfft_f32.c

 * Description:  RFFT & RIFFT Floating point process function

 *

 * $Date:        27. January 2017

 * $Revision:    V.1.5.1

 *

 * Target Processor: Cortex-M cores

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

/*

 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.

 *

 * SPDX-License-Identifier: Apache-2.0

 *

 * Licensed under the Apache License, Version 2.0 (the License); you may

 * not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 * www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an AS IS BASIS, WITHOUT

 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include "arm_math.h"

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

 * Internal functions prototypes

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

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);

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);

/**

* @ingroup groupTransforms

*/

/**

 * @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  It has been superceded by \ref arm_rfft_fast_f32 and will be removed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--;

  }

}