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56 mjames 1 
/* ----------------------------------------------------------------------
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 * Project:      CMSIS DSP Library
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 * Title:        arm_bitreversal.c
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 * Description:  Bitreversal functions
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 *
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 * $Date:        27. January 2017
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 * $Revision:    V.1.5.1
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 *
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 * Target Processor: Cortex-M cores
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 * -------------------------------------------------------------------- */
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/*
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 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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 *
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 * SPDX-License-Identifier: Apache-2.0
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 *
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 * Licensed under the Apache License, Version 2.0 (the License); you may
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 * not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 * www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
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 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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#include "arm_math.h"
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#include "arm_common_tables.h"
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/*
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* @brief  In-place bit reversal function.
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* @param[in, out] *pSrc        points to the in-place buffer of floating-point data type.
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* @param[in]      fftSize      length of the FFT.
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* @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table.
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* @param[in]      *pBitRevTab  points to the bit reversal table.
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* @return none.
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*/
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void arm_bitreversal_f32(
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float32_t * pSrc,
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uint16_t fftSize,
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uint16_t bitRevFactor,
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uint16_t * pBitRevTab)
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{
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   uint16_t fftLenBy2, fftLenBy2p1;
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   uint16_t i, j;
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   float32_t in;
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   /*  Initializations */
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   j = 0U;
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   fftLenBy2 = fftSize >> 1U;
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   fftLenBy2p1 = (fftSize >> 1U) + 1U;
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   /* Bit Reversal Implementation */
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   for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
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   {
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      if (i < j)
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      {
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         /*  pSrc[i] <-> pSrc[j]; */
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         in = pSrc[2U * i];
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         pSrc[2U * i] = pSrc[2U * j];
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         pSrc[2U * j] = in;
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         /*  pSrc[i+1U] <-> pSrc[j+1U] */
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         in = pSrc[(2U * i) + 1U];
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         pSrc[(2U * i) + 1U] = pSrc[(2U * j) + 1U];
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         pSrc[(2U * j) + 1U] = in;
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         /*  pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
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         in = pSrc[2U * (i + fftLenBy2p1)];
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         pSrc[2U * (i + fftLenBy2p1)] = pSrc[2U * (j + fftLenBy2p1)];
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         pSrc[2U * (j + fftLenBy2p1)] = in;
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         /*  pSrc[i+fftLenBy2p1+1U] <-> pSrc[j+fftLenBy2p1+1U] */
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         in = pSrc[(2U * (i + fftLenBy2p1)) + 1U];
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         pSrc[(2U * (i + fftLenBy2p1)) + 1U] =
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         pSrc[(2U * (j + fftLenBy2p1)) + 1U];
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         pSrc[(2U * (j + fftLenBy2p1)) + 1U] = in;
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      }
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      /*  pSrc[i+1U] <-> pSrc[j+1U] */
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      in = pSrc[2U * (i + 1U)];
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      pSrc[2U * (i + 1U)] = pSrc[2U * (j + fftLenBy2)];
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      pSrc[2U * (j + fftLenBy2)] = in;
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      /*  pSrc[i+2U] <-> pSrc[j+2U] */
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      in = pSrc[(2U * (i + 1U)) + 1U];
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      pSrc[(2U * (i + 1U)) + 1U] = pSrc[(2U * (j + fftLenBy2)) + 1U];
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      pSrc[(2U * (j + fftLenBy2)) + 1U] = in;
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      /*  Reading the index for the bit reversal */
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      j = *pBitRevTab;
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      /*  Updating the bit reversal index depending on the fft length  */
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      pBitRevTab += bitRevFactor;
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   }
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}
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/*
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* @brief  In-place bit reversal function.
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* @param[in, out] *pSrc        points to the in-place buffer of Q31 data type.
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* @param[in]      fftLen       length of the FFT.
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* @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
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* @param[in]      *pBitRevTab  points to bit reversal table.
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* @return none.
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*/
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void arm_bitreversal_q31(
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q31_t * pSrc,
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uint32_t fftLen,
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uint16_t bitRevFactor,
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uint16_t * pBitRevTable)
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{
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   uint32_t fftLenBy2, fftLenBy2p1, i, j;
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   q31_t in;
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   /*  Initializations      */
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   j = 0U;
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   fftLenBy2 = fftLen / 2U;
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   fftLenBy2p1 = (fftLen / 2U) + 1U;
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   /* Bit Reversal Implementation */
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   for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
129 
   {
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      if (i < j)
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      {
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         /*  pSrc[i] <-> pSrc[j]; */
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         in = pSrc[2U * i];
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         pSrc[2U * i] = pSrc[2U * j];
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         pSrc[2U * j] = in;
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         /*  pSrc[i+1U] <-> pSrc[j+1U] */
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         in = pSrc[(2U * i) + 1U];
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         pSrc[(2U * i) + 1U] = pSrc[(2U * j) + 1U];
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         pSrc[(2U * j) + 1U] = in;
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         /*  pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
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         in = pSrc[2U * (i + fftLenBy2p1)];
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         pSrc[2U * (i + fftLenBy2p1)] = pSrc[2U * (j + fftLenBy2p1)];
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         pSrc[2U * (j + fftLenBy2p1)] = in;
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         /*  pSrc[i+fftLenBy2p1+1U] <-> pSrc[j+fftLenBy2p1+1U] */
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         in = pSrc[(2U * (i + fftLenBy2p1)) + 1U];
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         pSrc[(2U * (i + fftLenBy2p1)) + 1U] =
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         pSrc[(2U * (j + fftLenBy2p1)) + 1U];
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         pSrc[(2U * (j + fftLenBy2p1)) + 1U] = in;
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153 
      }
154 
 
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      /*  pSrc[i+1U] <-> pSrc[j+1U] */
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      in = pSrc[2U * (i + 1U)];
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      pSrc[2U * (i + 1U)] = pSrc[2U * (j + fftLenBy2)];
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      pSrc[2U * (j + fftLenBy2)] = in;
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      /*  pSrc[i+2U] <-> pSrc[j+2U] */
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      in = pSrc[(2U * (i + 1U)) + 1U];
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      pSrc[(2U * (i + 1U)) + 1U] = pSrc[(2U * (j + fftLenBy2)) + 1U];
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      pSrc[(2U * (j + fftLenBy2)) + 1U] = in;
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      /*  Reading the index for the bit reversal */
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      j = *pBitRevTable;
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      /*  Updating the bit reversal index depending on the fft length */
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      pBitRevTable += bitRevFactor;
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   }
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}
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/*
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   * @brief  In-place bit reversal function.
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   * @param[in, out] *pSrc        points to the in-place buffer of Q15 data type.
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   * @param[in]      fftLen       length of the FFT.
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   * @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
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   * @param[in]      *pBitRevTab  points to bit reversal table.
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   * @return none.
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*/
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void arm_bitreversal_q15(
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q15_t * pSrc16,
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uint32_t fftLen,
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uint16_t bitRevFactor,
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uint16_t * pBitRevTab)
189 
{
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   q31_t *pSrc = (q31_t *) pSrc16;
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   q31_t in;
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   uint32_t fftLenBy2, fftLenBy2p1;
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   uint32_t i, j;
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195 
   /*  Initializations */
196 
   j = 0U;
197 
   fftLenBy2 = fftLen / 2U;
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   fftLenBy2p1 = (fftLen / 2U) + 1U;
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200 
   /* Bit Reversal Implementation */
201 
   for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
202 
   {
203 
      if (i < j)
204 
      {
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         /*  pSrc[i] <-> pSrc[j]; */
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         /*  pSrc[i+1U] <-> pSrc[j+1U] */
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         in = pSrc[i];
208 
         pSrc[i] = pSrc[j];
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         pSrc[j] = in;
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         /*  pSrc[i + fftLenBy2p1] <-> pSrc[j + fftLenBy2p1];  */
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         /*  pSrc[i + fftLenBy2p1+1U] <-> pSrc[j + fftLenBy2p1+1U] */
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         in = pSrc[i + fftLenBy2p1];
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         pSrc[i + fftLenBy2p1] = pSrc[j + fftLenBy2p1];
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         pSrc[j + fftLenBy2p1] = in;
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      }
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      /*  pSrc[i+1U] <-> pSrc[j+fftLenBy2];         */
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      /*  pSrc[i+2] <-> pSrc[j+fftLenBy2+1U]  */
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      in = pSrc[i + 1U];
221 
      pSrc[i + 1U] = pSrc[j + fftLenBy2];
222 
      pSrc[j + fftLenBy2] = in;
223 
 
224 
      /*  Reading the index for the bit reversal */
225 
      j = *pBitRevTab;
226 
 
227 
      /*  Updating the bit reversal index depending on the fft length  */
228 
      pBitRevTab += bitRevFactor;
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   }
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}