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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_bitreversal.c
* Description: Bitreversal functions
*
* $Date: 18. March 2019
* $Revision: V1.6.0
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2019 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"
#include "arm_common_tables.h"
/**
@brief In-place floating-point bit reversal function.
@param[in,out] pSrc points to in-place floating-point data buffer
@param[in] fftSize length of FFT
@param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
@param[in] pBitRevTab points to bit reversal table
@return none
*/
void arm_bitreversal_f32(
float32_t * pSrc,
uint16_t fftSize,
uint16_t bitRevFactor,
const uint16_t * pBitRevTab)
{
uint16_t fftLenBy2, fftLenBy2p1;
uint16_t i, j;
float32_t in;
/* Initializations */
j = 0U;
fftLenBy2 = fftSize >> 1U;
fftLenBy2p1 = (fftSize >> 1U) + 1U;
/* Bit Reversal Implementation */
for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
{
if (i < j)
{
/* pSrc[i] <-> pSrc[j]; */
in = pSrc[2U * i];
pSrc[2U * i] = pSrc[2U * j];
pSrc[2U * j] = in;
/* pSrc[i+1U] <-> pSrc[j+1U] */
in = pSrc[(2U * i) + 1U];
pSrc[(2U * i) + 1U] = pSrc[(2U * j) + 1U];
pSrc[(2U * j) + 1U] = in;
/* pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
in = pSrc[2U * (i + fftLenBy2p1)];
pSrc[2U * (i + fftLenBy2p1)] = pSrc[2U * (j + fftLenBy2p1)];
pSrc[2U * (j + fftLenBy2p1)] = in;
/* pSrc[i+fftLenBy2p1+1U] <-> pSrc[j+fftLenBy2p1+1U] */
in = pSrc[(2U * (i + fftLenBy2p1)) + 1U];
pSrc[(2U * (i + fftLenBy2p1)) + 1U] =
pSrc[(2U * (j + fftLenBy2p1)) + 1U];
pSrc[(2U * (j + fftLenBy2p1)) + 1U] = in;
}
/* pSrc[i+1U] <-> pSrc[j+1U] */
in = pSrc[2U * (i + 1U)];
pSrc[2U * (i + 1U)] = pSrc[2U * (j + fftLenBy2)];
pSrc[2U * (j + fftLenBy2)] = in;
/* pSrc[i+2U] <-> pSrc[j+2U] */
in = pSrc[(2U * (i + 1U)) + 1U];
pSrc[(2U * (i + 1U)) + 1U] = pSrc[(2U * (j + fftLenBy2)) + 1U];
pSrc[(2U * (j + fftLenBy2)) + 1U] = in;
/* Reading the index for the bit reversal */
j = *pBitRevTab;
/* Updating the bit reversal index depending on the fft length */
pBitRevTab += bitRevFactor;
}
}
/**
@brief In-place Q31 bit reversal function.
@param[in,out] pSrc points to in-place Q31 data buffer.
@param[in] fftLen length of FFT.
@param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
@param[in] pBitRevTab points to bit reversal table
@return none
*/
void arm_bitreversal_q31(
q31_t * pSrc,
uint32_t fftLen,
uint16_t bitRevFactor,
const uint16_t * pBitRevTab)
{
uint32_t fftLenBy2, fftLenBy2p1, i, j;
q31_t in;
/* Initializations */
j = 0U;
fftLenBy2 = fftLen / 2U;
fftLenBy2p1 = (fftLen / 2U) + 1U;
/* Bit Reversal Implementation */
for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
{
if (i < j)
{
/* pSrc[i] <-> pSrc[j]; */
in = pSrc[2U * i];
pSrc[2U * i] = pSrc[2U * j];
pSrc[2U * j] = in;
/* pSrc[i+1U] <-> pSrc[j+1U] */
in = pSrc[(2U * i) + 1U];
pSrc[(2U * i) + 1U] = pSrc[(2U * j) + 1U];
pSrc[(2U * j) + 1U] = in;
/* pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
in = pSrc[2U * (i + fftLenBy2p1)];
pSrc[2U * (i + fftLenBy2p1)] = pSrc[2U * (j + fftLenBy2p1)];
pSrc[2U * (j + fftLenBy2p1)] = in;
/* pSrc[i+fftLenBy2p1+1U] <-> pSrc[j+fftLenBy2p1+1U] */
in = pSrc[(2U * (i + fftLenBy2p1)) + 1U];
pSrc[(2U * (i + fftLenBy2p1)) + 1U] =
pSrc[(2U * (j + fftLenBy2p1)) + 1U];
pSrc[(2U * (j + fftLenBy2p1)) + 1U] = in;
}
/* pSrc[i+1U] <-> pSrc[j+1U] */
in = pSrc[2U * (i + 1U)];
pSrc[2U * (i + 1U)] = pSrc[2U * (j + fftLenBy2)];
pSrc[2U * (j + fftLenBy2)] = in;
/* pSrc[i+2U] <-> pSrc[j+2U] */
in = pSrc[(2U * (i + 1U)) + 1U];
pSrc[(2U * (i + 1U)) + 1U] = pSrc[(2U * (j + fftLenBy2)) + 1U];
pSrc[(2U * (j + fftLenBy2)) + 1U] = in;
/* Reading the index for the bit reversal */
j = *pBitRevTab;
/* Updating the bit reversal index depending on the fft length */
pBitRevTab += bitRevFactor;
}
}
/**
@brief In-place Q15 bit reversal function.
@param[in,out] pSrc16 points to in-place Q15 data buffer
@param[in] fftLen length of FFT
@param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
@param[in] pBitRevTab points to bit reversal table
@return none
*/
void arm_bitreversal_q15(
q15_t * pSrc16,
uint32_t fftLen,
uint16_t bitRevFactor,
const uint16_t * pBitRevTab)
{
q31_t *pSrc = (q31_t *) pSrc16;
q31_t in;
uint32_t fftLenBy2, fftLenBy2p1;
uint32_t i, j;
/* Initializations */
j = 0U;
fftLenBy2 = fftLen / 2U;
fftLenBy2p1 = (fftLen / 2U) + 1U;
/* Bit Reversal Implementation */
for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
{
if (i < j)
{
/* pSrc[i] <-> pSrc[j]; */
/* pSrc[i+1U] <-> pSrc[j+1U] */
in = pSrc[i];
pSrc[i] = pSrc[j];
pSrc[j] = in;
/* pSrc[i + fftLenBy2p1] <-> pSrc[j + fftLenBy2p1]; */
/* pSrc[i + fftLenBy2p1+1U] <-> pSrc[j + fftLenBy2p1+1U] */
in = pSrc[i + fftLenBy2p1];
pSrc[i + fftLenBy2p1] = pSrc[j + fftLenBy2p1];
pSrc[j + fftLenBy2p1] = in;
}
/* pSrc[i+1U] <-> pSrc[j+fftLenBy2]; */
/* pSrc[i+2] <-> pSrc[j+fftLenBy2+1U] */
in = pSrc[i + 1U];
pSrc[i + 1U] = pSrc[j + fftLenBy2];
pSrc[j + fftLenBy2] = in;
/* Reading the index for the bit reversal */
j = *pBitRevTab;
/* Updating the bit reversal index depending on the fft length */
pBitRevTab += bitRevFactor;
}
}
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