/* ---------------------------------------------------------------------- * Project: CMSIS DSP Library * Title: arm_bitreversal.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.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; } }