| /* ---------------------------------------------------------------------- | |
| * 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. | |
| */ | |
| /* | |
| * @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. | |
| */ | |
| 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; | |
| } | |
| } | |