208 lines
6.6 KiB
C
208 lines
6.6 KiB
C
/* ----------------------------------------------------------------------
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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: 18. March 2019
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* $Revision: V1.6.0
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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) 2010-2019 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_common_tables.h"
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#include "arm_math.h"
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/**
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@brief In-place floating-point bit reversal function.
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@param[in,out] pSrc points to in-place floating-point data buffer
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@param[in] fftSize length of FFT
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@param[in] bitRevFactor bit reversal modifier that supports different size
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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_f32(float32_t *pSrc, uint16_t fftSize,
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uint16_t bitRevFactor, const uint16_t *pBitRevTab) {
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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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if (i < j) {
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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] = 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 Q31 bit reversal function.
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@param[in,out] pSrc points to in-place Q31 data buffer.
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@param[in] fftLen length of FFT.
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@param[in] bitRevFactor bit reversal modifier that supports different size
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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(q31_t *pSrc, uint32_t fftLen, uint16_t bitRevFactor,
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const uint16_t *pBitRevTab) {
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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) {
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if (i < j) {
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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] = 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 Q15 bit reversal function.
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@param[in,out] pSrc16 points to in-place Q15 data buffer
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@param[in] fftLen length of FFT
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@param[in] bitRevFactor bit reversal modifier that supports different size
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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(q15_t *pSrc16, uint32_t fftLen, uint16_t bitRevFactor,
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const uint16_t *pBitRevTab) {
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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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/* 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) {
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if (i < j) {
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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];
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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];
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pSrc[i + 1U] = pSrc[j + fftLenBy2];
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pSrc[j + fftLenBy2] = 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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