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2 mjames 1 
/* ----------------------------------------------------------------------
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 * Project:      CMSIS DSP Library
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 * Title:        arm_cfft_init_f32.c
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 * Description:  Split Radix Decimation in Frequency CFFT Floating point processing function
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 *
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 * $Date:        27. January 2017
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 * $Revision:    V.1.5.1
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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) 2010-2017 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_math.h"
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#include "arm_common_tables.h"
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/**
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 * @ingroup groupTransforms
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 */
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/**
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 * @addtogroup RealFFT
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 * @{
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 */
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/**
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* @brief  Initialization function for the floating-point real FFT.
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* @param[in,out] *S             points to an arm_rfft_fast_instance_f32 structure.
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* @param[in]     fftLen         length of the Real Sequence.
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* @return        The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLen</code> is not a supported value.
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*
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* \par Description:
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* \par
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* The parameter <code>fftLen</code>     Specifies length of RFFT/CIFFT process. Supported FFT Lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096.
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* \par
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* This Function also initializes Twiddle factor table pointer and Bit reversal table pointer.
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*/
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arm_status arm_rfft_fast_init_f32(
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  arm_rfft_fast_instance_f32 * S,
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  uint16_t fftLen)
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{
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  arm_cfft_instance_f32 * Sint;
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  /*  Initialise the default arm status */
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  arm_status status = ARM_MATH_SUCCESS;
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  /*  Initialise the FFT length */
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  Sint = &(S->Sint);
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  Sint->fftLen = fftLen/2;
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  S->fftLenRFFT = fftLen;
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  /*  Initializations of structure parameters depending on the FFT length */
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  switch (Sint->fftLen)
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  {
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  case 2048U:
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    /*  Initializations of structure parameters for 2048 point FFT */
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    /*  Initialise the bit reversal table length */
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_2048_TABLE_LENGTH;
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    /*  Initialise the bit reversal table pointer */
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable2048;
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    /*  Initialise the Twiddle coefficient pointers */
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_2048;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_4096;
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    break;
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  case 1024U:
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_1024_TABLE_LENGTH;
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable1024;
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_1024;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_2048;
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    break;
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  case 512U:
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_512_TABLE_LENGTH;
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable512;
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_512;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_1024;
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    break;
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  case 256U:
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_256_TABLE_LENGTH;
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable256;
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_256;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_512;
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    break;
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  case 128U:
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_128_TABLE_LENGTH;
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable128;
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_128;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_256;
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    break;
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  case 64U:
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_64_TABLE_LENGTH;
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable64;
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_64;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_128;
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    break;
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  case 32U:
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_32_TABLE_LENGTH;
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable32;
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_32;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_64;
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    break;
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  case 16U:
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    Sint->bitRevLength = ARMBITREVINDEXTABLE_16_TABLE_LENGTH;
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    Sint->pBitRevTable = (uint16_t *)armBitRevIndexTable16;
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                Sint->pTwiddle     = (float32_t *) twiddleCoef_16;
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                S->pTwiddleRFFT    = (float32_t *) twiddleCoef_rfft_32;
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    break;
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  default:
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    /*  Reporting argument error if fftSize is not valid value */
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    status = ARM_MATH_ARGUMENT_ERROR;
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    break;
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  }
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  return (status);
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}
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/**
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 * @} end of RealFFT group
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 */