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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_bitreversal_f16.c
* Description: Bitreversal functions
*
* $Date: 23 April 2021
* $Revision: V1.9.0
*
* Target Processor: Cortex-M and Cortex-A cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2021 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 "dsp/transform_functions_f16.h"
/*
* @brief In-place bit reversal function.
* @param[in, out] *pSrc points to the in-place buffer of floating-point data type.
* @param[in] fftSize length of the FFT.
* @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table.
* @param[in] *pBitRevTab points to the bit reversal table.
* @return none.
*/
#if defined(ARM_FLOAT16_SUPPORTED)
void arm_bitreversal_f16(
float16_t * pSrc,
uint16_t fftSize,
uint16_t bitRevFactor,
const uint16_t * pBitRevTab)
{
uint16_t fftLenBy2, fftLenBy2p1;
uint16_t i, j;
float16_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;
}
}
#endif /* #if defined(ARM_FLOAT16_SUPPORTED) */
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