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/* ----------------------------------------------------------------------    

* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    

*    

* $Date:        19. March 2015

* $Revision:    V.1.4.5  

*    

* Project:          CMSIS DSP Library    

* Title:            arm_rfft_q31.c    

*    

* Description:  RFFT & RIFFT Q31 process function    

*    

*    

* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0

*  

* Redistribution and use in source and binary forms, with or without

* modification, are permitted provided that the following conditions

* are met:

*   - Redistributions of source code must retain the above copyright

*     notice, this list of conditions and the following disclaimer.

*   - Redistributions in binary form must reproduce the above copyright

*     notice, this list of conditions and the following disclaimer in

*     the documentation and/or other materials provided with the

*     distribution.

*   - Neither the name of ARM LIMITED nor the names of its contributors

*     may be used to endorse or promote products derived from this

*     software without specific prior written permission.

*

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS

* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE

* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,

* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,

* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER

* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

* POSSIBILITY OF SUCH DAMAGE.    

* -------------------------------------------------------------------- */

#include "arm_math.h"

/*--------------------------------------------------------------------    

*               Internal functions prototypes    

--------------------------------------------------------------------*/

void arm_split_rfft_q31(

    q31_t * pSrc,

    uint32_t fftLen,

    q31_t * pATable,

    q31_t * pBTable,

    q31_t * pDst,

    uint32_t modifier);

void arm_split_rifft_q31(

    q31_t * pSrc,

    uint32_t fftLen,

    q31_t * pATable,

    q31_t * pBTable,

    q31_t * pDst,

    uint32_t modifier);

/**    

* @addtogroup RealFFT    

* @{    

*/

/**    

* @brief Processing function for the Q31 RFFT/RIFFT.  

* @param[in]  *S    points to an instance of the Q31 RFFT/RIFFT structure.  

* @param[in]  *pSrc points to the input buffer.  

* @param[out] *pDst points to the output buffer.  

* @return none.  

*    

* \par Input an output formats:  

* \par    

* Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process.  

* Hence the output format is different for different RFFT sizes.    

* The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:  

* \par    

* \image html RFFTQ31.gif "Input and Output Formats for Q31 RFFT"    

*    

* \par    

* \image html RIFFTQ31.gif "Input and Output Formats for Q31 RIFFT"    

*/

void arm_rfft_q31(

    const arm_rfft_instance_q31 * S,

    q31_t * pSrc,

    q31_t * pDst)

{

    const arm_cfft_instance_q31 *S_CFFT = S->pCfft;

    uint32_t i;

    uint32_t L2 = S->fftLenReal >> 1;

    /* Calculation of RIFFT of input */

    if(S->ifftFlagR == 1u)

    {

        /*  Real IFFT core process */

        arm_split_rifft_q31(pSrc, L2, S->pTwiddleAReal,

                            S->pTwiddleBReal, pDst, S->twidCoefRModifier);

        /* Complex IFFT process */

        arm_cfft_q31(S_CFFT, pDst, S->ifftFlagR, S->bitReverseFlagR);

        for(i=0;i<S->fftLenReal;i++)

        {

            pDst[i] = pDst[i] << 1;

        }

    }

    else

    {

        /* Calculation of RFFT of input */

        /* Complex FFT process */

        arm_cfft_q31(S_CFFT, pSrc, S->ifftFlagR, S->bitReverseFlagR);

        /*  Real FFT core process */

        arm_split_rfft_q31(pSrc, L2, S->pTwiddleAReal,

                            S->pTwiddleBReal, pDst, S->twidCoefRModifier);

    }

}

/**    

* @} end of RealFFT group    

*/

/**    

* @brief  Core Real FFT process    

* @param[in]   *pSrc                            points to the input buffer.    

* @param[in]   fftLen                       length of FFT.  

* @param[in]   *pATable                         points to the twiddle Coef A buffer.    

* @param[in]   *pBTable                         points to the twiddle Coef B buffer.    

* @param[out]  *pDst                            points to the output buffer.    

* @param[in]   modifier                 twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.  

* @return none.    

*/

void arm_split_rfft_q31(

    q31_t * pSrc,

    uint32_t fftLen,

    q31_t * pATable,

    q31_t * pBTable,

    q31_t * pDst,

    uint32_t modifier)

{

    uint32_t i;                                    /* Loop Counter */

    q31_t outR, outI;                              /* Temporary variables for output */

    q31_t *pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */

    q31_t CoefA1, CoefA2, CoefB1;                  /* Temporary variables for twiddle coefficients */

    q31_t *pOut1 = &pDst[2], *pOut2 = &pDst[(4u * fftLen) - 1u];

    q31_t *pIn1 = &pSrc[2], *pIn2 = &pSrc[(2u * fftLen) - 1u];

    /* Init coefficient pointers */

    pCoefA = &pATable[modifier * 2u];

    pCoefB = &pBTable[modifier * 2u];

    i = fftLen - 1u;

    while(i > 0u)

    {

        /*    

        outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]    

        + pSrc[2 * n - 2 * i] * pBTable[2 * i] +    

        pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    

        */

        /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +    

        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    

        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */

        CoefA1 = *pCoefA++;

        CoefA2 = *pCoefA;

        /* outR = (pSrc[2 * i] * pATable[2 * i] */    

        mult_32x32_keep32_R(outR, *pIn1, CoefA1);

        /* outI = pIn[2 * i] * pATable[2 * i + 1] */

        mult_32x32_keep32_R(outI, *pIn1++, CoefA2);

        /* - pSrc[2 * i + 1] * pATable[2 * i + 1] */

        multSub_32x32_keep32_R(outR, *pIn1, CoefA2);

        /* (pIn[2 * i + 1] * pATable[2 * i] */

        multAcc_32x32_keep32_R(outI, *pIn1++, CoefA1);

        /* pSrc[2 * n - 2 * i] * pBTable[2 * i]  */

        multSub_32x32_keep32_R(outR, *pIn2, CoefA2);

        CoefB1 = *pCoefB;

        /* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */

        multSub_32x32_keep32_R(outI, *pIn2--, CoefB1);

        /* pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */

        multAcc_32x32_keep32_R(outR, *pIn2, CoefB1);

        /* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */

        multSub_32x32_keep32_R(outI, *pIn2--, CoefA2);

        /* write output */

        *pOut1++ = outR;

        *pOut1++ = outI;

        /* write complex conjugate output */

        *pOut2-- = -outI;

        *pOut2-- = outR;

        /* update coefficient pointer */

        pCoefB = pCoefB + (modifier * 2u);

        pCoefA = pCoefA + ((modifier * 2u) - 1u);

        i--;

    }

    pDst[2u * fftLen] = (pSrc[0] - pSrc[1]) >> 1;

    pDst[(2u * fftLen) + 1u] = 0;

    pDst[0] = (pSrc[0] + pSrc[1]) >> 1;

    pDst[1] = 0;

}

/**    

* @brief  Core Real IFFT process    

* @param[in]   *pSrc                            points to the input buffer.  

* @param[in]   fftLen                       length of FFT.    

* @param[in]   *pATable                         points to the twiddle Coef A buffer.  

* @param[in]   *pBTable                         points to the twiddle Coef B buffer.    

* @param[out]  *pDst                            points to the output buffer.  

* @param[in]   modifier                 twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.  

* @return none.    

*/

void arm_split_rifft_q31(

    q31_t * pSrc,

    uint32_t fftLen,

    q31_t * pATable,

    q31_t * pBTable,

    q31_t * pDst,

    uint32_t modifier)

{

    q31_t outR, outI;                              /* Temporary variables for output */

    q31_t *pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */

    q31_t CoefA1, CoefA2, CoefB1;                  /* Temporary variables for twiddle coefficients */

    q31_t *pIn1 = &pSrc[0], *pIn2 = &pSrc[(2u * fftLen) + 1u];

    pCoefA = &pATable[0];

    pCoefB = &pBTable[0];

    while(fftLen > 0u)

    {

        /*    

        outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +    

        pIn[2 * n - 2 * i] * pBTable[2 * i] -    

        pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    

        outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -    

        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    

        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);  

        */

        CoefA1 = *pCoefA++;

        CoefA2 = *pCoefA;

        /* outR = (pIn[2 * i] * pATable[2 * i] */

        mult_32x32_keep32_R(outR, *pIn1, CoefA1);

        /* - pIn[2 * i] * pATable[2 * i + 1] */

        mult_32x32_keep32_R(outI, *pIn1++, -CoefA2);

        /* pIn[2 * i + 1] * pATable[2 * i + 1] */

        multAcc_32x32_keep32_R(outR, *pIn1, CoefA2);

        /* pIn[2 * i + 1] * pATable[2 * i] */

        multAcc_32x32_keep32_R(outI, *pIn1++, CoefA1);

        /* pIn[2 * n - 2 * i] * pBTable[2 * i] */

        multAcc_32x32_keep32_R(outR, *pIn2, CoefA2);

        CoefB1 = *pCoefB;

        /* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */

        multSub_32x32_keep32_R(outI, *pIn2--, CoefB1);

        /* pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */

        multAcc_32x32_keep32_R(outR, *pIn2, CoefB1);

        /* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */

        multAcc_32x32_keep32_R(outI, *pIn2--, CoefA2);

        /* write output */

        *pDst++ = outR;

        *pDst++ = outI;

        /* update coefficient pointer */

        pCoefB = pCoefB + (modifier * 2u);

        pCoefA = pCoefA + ((modifier * 2u) - 1u);

        /* Decrement loop count */

        fftLen--;

    }

}