/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date: 16/10/14 6:01p $Revision:  V.1.4.5
*
* Project:      CMSIS DSP Library
* Title:        arm_fir_lattice_q15.c
*
* Description:  Q15 FIR lattice filter processing 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"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_Lattice
 * @{
 */


/**
 * @brief Processing function for the Q15 FIR lattice filter.
 * @param[in]  *S        points to an instance of the Q15 FIR lattice structure.
 * @param[in]  *pSrc     points to the block of input data.
 * @param[out] *pDst     points to the block of output data
 * @param[in]  blockSize number of samples to process.
 * @return none.
 */

void arm_fir_lattice_q15(
    const arm_fir_lattice_instance_q15 * S,
    q15_t * pSrc,
    q15_t * pDst,
    uint32_t blockSize)
{
    q15_t *pState;                                 /* State pointer */
    q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    q15_t *px;                                     /* temporary state pointer */
    q15_t *pk;                                     /* temporary coefficient pointer */


#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */

    q31_t fcurnt1, fnext1, gcurnt1 = 0, gnext1;    /* temporary variables for first sample in loop unrolling */
    q31_t fcurnt2, fnext2, gnext2;                 /* temporary variables for second sample in loop unrolling */
    q31_t fcurnt3, fnext3, gnext3;                 /* temporary variables for third sample in loop unrolling */
    q31_t fcurnt4, fnext4, gnext4;                 /* temporary variables for fourth sample in loop unrolling */
    uint32_t numStages = S->numStages;             /* Number of stages in the filter */
    uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

    pState = &S->pState[0];

    blkCnt = blockSize >> 2u;

    /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
     ** a second loop below computes the remaining 1 to 3 samples. */
    while(blkCnt > 0u)
    {

        /* Read two samples from input buffer */
        /* f0(n) = x(n) */
        fcurnt1 = *pSrc++;
        fcurnt2 = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* Read g0(n-1) from state */
        gcurnt1 = *px;

        /* Process first sample for first tap */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
        fnext1 = __SSAT(fnext1, 16);

        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext1 = (q31_t)((fcurnt1 * (*pk)) >> 15u) + gcurnt1;
        gnext1 = __SSAT(gnext1, 16);

        /* Process second sample for first tap */
        /* for sample 2 processing */
        fnext2 = (q31_t)((fcurnt1 * (*pk)) >> 15u) + fcurnt2;
        fnext2 = __SSAT(fnext2, 16);

        gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + fcurnt1;
        gnext2 = __SSAT(gnext2, 16);


        /* Read next two samples from input buffer */
        /* f0(n+2) = x(n+2) */
        fcurnt3 = *pSrc++;
        fcurnt4 = *pSrc++;

        /* Copy only last input samples into the state buffer
           which is used for next four samples processing */
        *px++ = (q15_t) fcurnt4;

        /* Process third sample for first tap */
        fnext3 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + fcurnt3;
        fnext3 = __SSAT(fnext3, 16);
        gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + fcurnt2;
        gnext3 = __SSAT(gnext3, 16);

        /* Process fourth sample for first tap */
        fnext4 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + fcurnt4;
        fnext4 = __SSAT(fnext4, 16);
        gnext4 = (q31_t)((fcurnt4 * (*pk++)) >> 15u) + fcurnt3;
        gnext4 = __SSAT(gnext4, 16);

        /* Update of f values for next coefficient set processing */
        fcurnt1 = fnext1;
        fcurnt2 = fnext2;
        fcurnt3 = fnext3;
        fcurnt4 = fnext4;


        /* Loop unrolling.  Process 4 taps at a time . */
        stageCnt = (numStages - 1u) >> 2;


        /* Loop over the number of taps.  Unroll by a factor of 4.
         ** Repeat until we've computed numStages-3 coefficients. */

        /* Process 2nd, 3rd, 4th and 5th taps ... here */
        while(stageCnt > 0u)
        {
            /* Read g1(n-1), g3(n-1) .... from state */
            gcurnt1 = *px;

            /* save g1(n) in state buffer */
            *px++ = (q15_t) gnext4;

            /* Process first sample for 2nd, 6th .. tap */
            /* Sample processing for K2, K6.... */
            /* f1(n) = f0(n) +  K1 * g0(n-1) */
            fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
            fnext1 = __SSAT(fnext1, 16);


            /* Process second sample for 2nd, 6th .. tap */
            /* for sample 2 processing */
            fnext2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fcurnt2;
            fnext2 = __SSAT(fnext2, 16);
            /* Process third sample for 2nd, 6th .. tap */
            fnext3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fcurnt3;
            fnext3 = __SSAT(fnext3, 16);
            /* Process fourth sample for 2nd, 6th .. tap */
            /* fnext4 = fcurnt4 + (*pk) * gnext3; */
            fnext4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fcurnt4;
            fnext4 = __SSAT(fnext4, 16);

            /* g1(n) = f0(n) * K1  +  g0(n-1) */
            /* Calculation of state values for next stage */
            gnext4 = (q31_t)((fcurnt4 * (*pk)) >> 15u) + gnext3;
            gnext4 = __SSAT(gnext4, 16);
            gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + gnext2;
            gnext3 = __SSAT(gnext3, 16);

            gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + gnext1;
            gnext2 = __SSAT(gnext2, 16);

            gnext1 = (q31_t)((fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
            gnext1 = __SSAT(gnext1, 16);


            /* Read g2(n-1), g4(n-1) .... from state */
            gcurnt1 = *px;

            /* save g1(n) in state buffer */
            *px++ = (q15_t) gnext4;

            /* Sample processing for K3, K7.... */
            /* Process first sample for 3rd, 7th .. tap */
            /* f3(n) = f2(n) +  K3 * g2(n-1) */
            fcurnt1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fnext1;
            fcurnt1 = __SSAT(fcurnt1, 16);

            /* Process second sample for 3rd, 7th .. tap */
            fcurnt2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fnext2;
            fcurnt2 = __SSAT(fcurnt2, 16);

            /* Process third sample for 3rd, 7th .. tap */
            fcurnt3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fnext3;
            fcurnt3 = __SSAT(fcurnt3, 16);

            /* Process fourth sample for 3rd, 7th .. tap */
            fcurnt4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fnext4;
            fcurnt4 = __SSAT(fcurnt4, 16);

            /* Calculation of state values for next stage */
            /* g3(n) = f2(n) * K3  +  g2(n-1) */
            gnext4 = (q31_t)((fnext4 * (*pk)) >> 15u) + gnext3;
            gnext4 = __SSAT(gnext4, 16);

            gnext3 = (q31_t)((fnext3 * (*pk)) >> 15u) + gnext2;
            gnext3 = __SSAT(gnext3, 16);

            gnext2 = (q31_t)((fnext2 * (*pk)) >> 15u) + gnext1;
            gnext2 = __SSAT(gnext2, 16);

            gnext1 = (q31_t)((fnext1 * (*pk++)) >> 15u) + gcurnt1;
            gnext1 = __SSAT(gnext1, 16);

            /* Read g1(n-1), g3(n-1) .... from state */
            gcurnt1 = *px;

            /* save g1(n) in state buffer */
            *px++ = (q15_t) gnext4;

            /* Sample processing for K4, K8.... */
            /* Process first sample for 4th, 8th .. tap */
            /* f4(n) = f3(n) +  K4 * g3(n-1) */
            fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
            fnext1 = __SSAT(fnext1, 16);

            /* Process second sample for 4th, 8th .. tap */
            /* for sample 2 processing */
            fnext2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fcurnt2;
            fnext2 = __SSAT(fnext2, 16);

            /* Process third sample for 4th, 8th .. tap */
            fnext3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fcurnt3;
            fnext3 = __SSAT(fnext3, 16);

            /* Process fourth sample for 4th, 8th .. tap */
            fnext4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fcurnt4;
            fnext4 = __SSAT(fnext4, 16);

            /* g4(n) = f3(n) * K4  +  g3(n-1) */
            /* Calculation of state values for next stage */
            gnext4 = (q31_t)((fcurnt4 * (*pk)) >> 15u) + gnext3;
            gnext4 = __SSAT(gnext4, 16);

            gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + gnext2;
            gnext3 = __SSAT(gnext3, 16);

            gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + gnext1;
            gnext2 = __SSAT(gnext2, 16);
            gnext1 = (q31_t)((fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
            gnext1 = __SSAT(gnext1, 16);


            /* Read g2(n-1), g4(n-1) .... from state */
            gcurnt1 = *px;

            /* save g4(n) in state buffer */
            *px++ = (q15_t) gnext4;

            /* Sample processing for K5, K9.... */
            /* Process first sample for 5th, 9th .. tap */
            /* f5(n) = f4(n) +  K5 * g4(n-1) */
            fcurnt1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fnext1;
            fcurnt1 = __SSAT(fcurnt1, 16);

            /* Process second sample for 5th, 9th .. tap */
            fcurnt2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fnext2;
            fcurnt2 = __SSAT(fcurnt2, 16);

            /* Process third sample for 5th, 9th .. tap */
            fcurnt3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fnext3;
            fcurnt3 = __SSAT(fcurnt3, 16);

            /* Process fourth sample for 5th, 9th .. tap */
            fcurnt4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fnext4;
            fcurnt4 = __SSAT(fcurnt4, 16);

            /* Calculation of state values for next stage */
            /* g5(n) = f4(n) * K5  +  g4(n-1) */
            gnext4 = (q31_t)((fnext4 * (*pk)) >> 15u) + gnext3;
            gnext4 = __SSAT(gnext4, 16);
            gnext3 = (q31_t)((fnext3 * (*pk)) >> 15u) + gnext2;
            gnext3 = __SSAT(gnext3, 16);
            gnext2 = (q31_t)((fnext2 * (*pk)) >> 15u) + gnext1;
            gnext2 = __SSAT(gnext2, 16);
            gnext1 = (q31_t)((fnext1 * (*pk++)) >> 15u) + gcurnt1;
            gnext1 = __SSAT(gnext1, 16);

            stageCnt--;
        }

        /* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
        stageCnt = (numStages - 1u) % 0x4u;

        while(stageCnt > 0u)
        {
            gcurnt1 = *px;

            /* save g value in state buffer */
            *px++ = (q15_t) gnext4;

            /* Process four samples for last three taps here */
            fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
            fnext1 = __SSAT(fnext1, 16);
            fnext2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fcurnt2;
            fnext2 = __SSAT(fnext2, 16);

            fnext3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fcurnt3;
            fnext3 = __SSAT(fnext3, 16);

            fnext4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fcurnt4;
            fnext4 = __SSAT(fnext4, 16);

            /* g1(n) = f0(n) * K1  +  g0(n-1) */
            gnext4 = (q31_t)((fcurnt4 * (*pk)) >> 15u) + gnext3;
            gnext4 = __SSAT(gnext4, 16);
            gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + gnext2;
            gnext3 = __SSAT(gnext3, 16);
            gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + gnext1;
            gnext2 = __SSAT(gnext2, 16);
            gnext1 = (q31_t)((fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
            gnext1 = __SSAT(gnext1, 16);

            /* Update of f values for next coefficient set processing */
            fcurnt1 = fnext1;
            fcurnt2 = fnext2;
            fcurnt3 = fnext3;
            fcurnt4 = fnext4;

            stageCnt--;

        }

        /* The results in the 4 accumulators, store in the destination buffer. */
        /* y(n) = fN(n) */

#ifndef  ARM_MATH_BIG_ENDIAN

        *__SIMD32(pDst)++ = __PKHBT(fcurnt1, fcurnt2, 16);
        *__SIMD32(pDst)++ = __PKHBT(fcurnt3, fcurnt4, 16);

#else

        *__SIMD32(pDst)++ = __PKHBT(fcurnt2, fcurnt1, 16);
        *__SIMD32(pDst)++ = __PKHBT(fcurnt4, fcurnt3, 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

        blkCnt--;
    }

    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
     ** No loop unrolling is used. */
    blkCnt = blockSize % 0x4u;

    while(blkCnt > 0u)
    {
        /* f0(n) = x(n) */
        fcurnt1 = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* read g2(n) from state buffer */
        gcurnt1 = *px;

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext1 = (((q31_t) gcurnt1 * (*pk)) >> 15u) + fcurnt1;
        fnext1 = __SSAT(fnext1, 16);


        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext1 = (((q31_t) fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
        gnext1 = __SSAT(gnext1, 16);

        /* save g1(n) in state buffer */
        *px++ = (q15_t) fcurnt1;

        /* f1(n) is saved in fcurnt1
           for next stage processing */
        fcurnt1 = fnext1;

        stageCnt = (numStages - 1u);

        /* stage loop */
        while(stageCnt > 0u)
        {
            /* read g2(n) from state buffer */
            gcurnt1 = *px;

            /* save g1(n) in state buffer */
            *px++ = (q15_t) gnext1;

            /* Sample processing for K2, K3.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext1 = (((q31_t) gcurnt1 * (*pk)) >> 15u) + fcurnt1;
            fnext1 = __SSAT(fnext1, 16);

            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext1 = (((q31_t) fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
            gnext1 = __SSAT(gnext1, 16);


            /* f1(n) is saved in fcurnt1
               for next stage processing */
            fcurnt1 = fnext1;

            stageCnt--;

        }

        /* y(n) = fN(n) */
        *pDst++ = __SSAT(fcurnt1, 16);


        blkCnt--;

    }

#else

    /* Run the below code for Cortex-M0 */

    q31_t fcurnt, fnext, gcurnt, gnext;            /* temporary variables */
    uint32_t numStages = S->numStages;             /* Length of the filter */
    uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

    pState = &S->pState[0];

    blkCnt = blockSize;

    while(blkCnt > 0u)
    {
        /* f0(n) = x(n) */
        fcurnt = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* read g0(n-1) from state buffer */
        gcurnt = *px;

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext = ((gcurnt * (*pk)) >> 15u) + fcurnt;
        fnext = __SSAT(fnext, 16);


        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext = ((fcurnt * (*pk++)) >> 15u) + gcurnt;
        gnext = __SSAT(gnext, 16);

        /* save f0(n) in state buffer */
        *px++ = (q15_t) fcurnt;

        /* f1(n) is saved in fcurnt
           for next stage processing */
        fcurnt = fnext;

        stageCnt = (numStages - 1u);

        /* stage loop */
        while(stageCnt > 0u)
        {
            /* read g1(n-1) from state buffer */
            gcurnt = *px;

            /* save g0(n-1) in state buffer */
            *px++ = (q15_t) gnext;

            /* Sample processing for K2, K3.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext = ((gcurnt * (*pk)) >> 15u) + fcurnt;
            fnext = __SSAT(fnext, 16);

            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext = ((fcurnt * (*pk++)) >> 15u) + gcurnt;
            gnext = __SSAT(gnext, 16);


            /* f1(n) is saved in fcurnt
               for next stage processing */
            fcurnt = fnext;

            stageCnt--;

        }

        /* y(n) = fN(n) */
        *pDst++ = __SSAT(fcurnt, 16);


        blkCnt--;

    }

#endif /*   #ifndef ARM_MATH_CM0_FAMILY */

}

/**
 * @} end of FIR_Lattice group
 */
