File content as of revision 3:4098b9d3d571:

/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_cfft_q31.c
 * Description:  Combined Radix Decimation in Frequency CFFT fixed point processing function
 *
 * $Date:        27. January 2017
 * $Revision:    V.1.5.1
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2017 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 "arm_math.h"

extern void arm_radix4_butterfly_q31(
    q31_t * pSrc,
    uint32_t fftLen,
    q31_t * pCoef,
    uint32_t twidCoefModifier);

extern void arm_radix4_butterfly_inverse_q31(
    q31_t * pSrc,
    uint32_t fftLen,
    q31_t * pCoef,
    uint32_t twidCoefModifier);

extern void arm_bitreversal_32(
    uint32_t * pSrc,
    const uint16_t bitRevLen,
    const uint16_t * pBitRevTable);

void arm_cfft_radix4by2_q31(
    q31_t * pSrc,
    uint32_t fftLen,
    const q31_t * pCoef);

void arm_cfft_radix4by2_inverse_q31(
    q31_t * pSrc,
    uint32_t fftLen,
    const q31_t * pCoef);

/**
* @ingroup groupTransforms
*/

/**
* @addtogroup ComplexFFT
* @{
*/

/**
* @details
* @brief       Processing function for the fixed-point complex FFT in Q31 format.
* @param[in]      *S    points to an instance of the fixed-point CFFT structure.
* @param[in, out] *p1   points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.
* @param[in]     ifftFlag       flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.
* @param[in]     bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
* @return none.
*/

void arm_cfft_q31(
    const arm_cfft_instance_q31 * S,
    q31_t * p1,
    uint8_t ifftFlag,
    uint8_t bitReverseFlag)
{
    uint32_t L = S->fftLen;

    if (ifftFlag == 1U)
    {
        switch (L)
        {
        case 16:
        case 64:
        case 256:
        case 1024:
        case 4096:
            arm_radix4_butterfly_inverse_q31  ( p1, L, (q31_t*)S->pTwiddle, 1 );
            break;

        case 32:
        case 128:
        case 512:
        case 2048:
            arm_cfft_radix4by2_inverse_q31  ( p1, L, S->pTwiddle );
            break;
        }
    }
    else
    {
        switch (L)
        {
        case 16:
        case 64:
        case 256:
        case 1024:
        case 4096:
            arm_radix4_butterfly_q31  ( p1, L, (q31_t*)S->pTwiddle, 1 );
            break;

        case 32:
        case 128:
        case 512:
        case 2048:
            arm_cfft_radix4by2_q31  ( p1, L, S->pTwiddle );
            break;
        }
    }

    if ( bitReverseFlag )
        arm_bitreversal_32((uint32_t*)p1,S->bitRevLength,S->pBitRevTable);
}

/**
* @} end of ComplexFFT group
*/

void arm_cfft_radix4by2_q31(
    q31_t * pSrc,
    uint32_t fftLen,
    const q31_t * pCoef)
{
    uint32_t i, l;
    uint32_t n2, ia;
    q31_t xt, yt, cosVal, sinVal;
    q31_t p0, p1;

    n2 = fftLen >> 1;
    ia = 0;
    for (i = 0; i < n2; i++)
    {
        cosVal = pCoef[2*ia];
        sinVal = pCoef[2*ia + 1];
        ia++;

        l = i + n2;
        xt = (pSrc[2 * i] >> 2) - (pSrc[2 * l] >> 2);
        pSrc[2 * i] = (pSrc[2 * i] >> 2) + (pSrc[2 * l] >> 2);

        yt = (pSrc[2 * i + 1] >> 2) - (pSrc[2 * l + 1] >> 2);
        pSrc[2 * i + 1] = (pSrc[2 * l + 1] >> 2) + (pSrc[2 * i + 1] >> 2);

        mult_32x32_keep32_R(p0, xt, cosVal);
        mult_32x32_keep32_R(p1, yt, cosVal);
        multAcc_32x32_keep32_R(p0, yt, sinVal);
        multSub_32x32_keep32_R(p1, xt, sinVal);

        pSrc[2U * l] = p0 << 1;
        pSrc[2U * l + 1U] = p1 << 1;

    }

    // first col
    arm_radix4_butterfly_q31( pSrc, n2, (q31_t*)pCoef, 2U);
    // second col
    arm_radix4_butterfly_q31( pSrc + fftLen, n2, (q31_t*)pCoef, 2U);

    for (i = 0; i < fftLen >> 1; i++)
    {
        p0 = pSrc[4*i+0];
        p1 = pSrc[4*i+1];
        xt = pSrc[4*i+2];
        yt = pSrc[4*i+3];

        p0 <<= 1;
        p1 <<= 1;
        xt <<= 1;
        yt <<= 1;

        pSrc[4*i+0] = p0;
        pSrc[4*i+1] = p1;
        pSrc[4*i+2] = xt;
        pSrc[4*i+3] = yt;
    }

}

void arm_cfft_radix4by2_inverse_q31(
    q31_t * pSrc,
    uint32_t fftLen,
    const q31_t * pCoef)
{
    uint32_t i, l;
    uint32_t n2, ia;
    q31_t xt, yt, cosVal, sinVal;
    q31_t p0, p1;

    n2 = fftLen >> 1;
    ia = 0;
    for (i = 0; i < n2; i++)
    {
        cosVal = pCoef[2*ia];
        sinVal = pCoef[2*ia + 1];
        ia++;

        l = i + n2;
        xt = (pSrc[2 * i] >> 2) - (pSrc[2 * l] >> 2);
        pSrc[2 * i] = (pSrc[2 * i] >> 2) + (pSrc[2 * l] >> 2);

        yt = (pSrc[2 * i + 1] >> 2) - (pSrc[2 * l + 1] >> 2);
        pSrc[2 * i + 1] = (pSrc[2 * l + 1] >> 2) + (pSrc[2 * i + 1] >> 2);

        mult_32x32_keep32_R(p0, xt, cosVal);
        mult_32x32_keep32_R(p1, yt, cosVal);
        multSub_32x32_keep32_R(p0, yt, sinVal);
        multAcc_32x32_keep32_R(p1, xt, sinVal);

        pSrc[2U * l] = p0 << 1;
        pSrc[2U * l + 1U] = p1 << 1;

    }

    // first col
    arm_radix4_butterfly_inverse_q31( pSrc, n2, (q31_t*)pCoef, 2U);
    // second col
    arm_radix4_butterfly_inverse_q31( pSrc + fftLen, n2, (q31_t*)pCoef, 2U);

    for (i = 0; i < fftLen >> 1; i++)
    {
        p0 = pSrc[4*i+0];
        p1 = pSrc[4*i+1];
        xt = pSrc[4*i+2];
        yt = pSrc[4*i+3];

        p0 <<= 1;
        p1 <<= 1;
        xt <<= 1;
        yt <<= 1;

        pSrc[4*i+0] = p0;
        pSrc[4*i+1] = p1;
        pSrc[4*i+2] = xt;
        pSrc[4*i+3] = yt;
    }
}