/* ----------------------------------------------------------------------
* 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_conv_partial_q31.c
*
* Description:  Partial convolution of Q31 sequences.
*
* 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,
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* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup PartialConv
 * @{
 */

/**
 * @brief Partial convolution of Q31 sequences.
 * @param[in]       *pSrcA points to the first input sequence.
 * @param[in]       srcALen length of the first input sequence.
 * @param[in]       *pSrcB points to the second input sequence.
 * @param[in]       srcBLen length of the second input sequence.
 * @param[out]      *pDst points to the location where the output result is written.
 * @param[in]       firstIndex is the first output sample to start with.
 * @param[in]       numPoints is the number of output points to be computed.
 * @return Returns either ARM_MATH_SUCCESS if the function completed correctly or ARM_MATH_ARGUMENT_ERROR if the requested subset is not in the range [0 srcALen+srcBLen-2].
 *
 * See <code>arm_conv_partial_fast_q31()</code> for a faster but less precise implementation of this function for Cortex-M3 and Cortex-M4.
 */

arm_status arm_conv_partial_q31(
    q31_t * pSrcA,
    uint32_t srcALen,
    q31_t * pSrcB,
    uint32_t srcBLen,
    q31_t * pDst,
    uint32_t firstIndex,
    uint32_t numPoints)
{


#ifndef ARM_MATH_CM0_FAMILY

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

    q31_t *pIn1;                                   /* inputA pointer               */
    q31_t *pIn2;                                   /* inputB pointer               */
    q31_t *pOut = pDst;                            /* output pointer               */
    q31_t *px;                                     /* Intermediate inputA pointer  */
    q31_t *py;                                     /* Intermediate inputB pointer  */
    q31_t *pSrc1, *pSrc2;                          /* Intermediate pointers        */
    q63_t sum, acc0, acc1, acc2;                   /* Accumulator                  */
    q31_t x0, x1, x2, c0;
    uint32_t j, k, count, check, blkCnt;
    int32_t blockSize1, blockSize2, blockSize3;    /* loop counter                 */
    arm_status status;                             /* status of Partial convolution */


    /* Check for range of output samples to be calculated */
    if((firstIndex + numPoints) > ((srcALen + (srcBLen - 1u))))
    {
        /* Set status as ARM_MATH_ARGUMENT_ERROR */
        status = ARM_MATH_ARGUMENT_ERROR;
    }
    else
    {

        /* The algorithm implementation is based on the lengths of the inputs. */
        /* srcB is always made to slide across srcA. */
        /* So srcBLen is always considered as shorter or equal to srcALen */
        if(srcALen >= srcBLen)
        {
            /* Initialization of inputA pointer */
            pIn1 = pSrcA;

            /* Initialization of inputB pointer */
            pIn2 = pSrcB;
        }
        else
        {
            /* Initialization of inputA pointer */
            pIn1 = pSrcB;

            /* Initialization of inputB pointer */
            pIn2 = pSrcA;

            /* srcBLen is always considered as shorter or equal to srcALen */
            j = srcBLen;
            srcBLen = srcALen;
            srcALen = j;
        }

        /* Conditions to check which loopCounter holds
         * the first and last indices of the output samples to be calculated. */
        check = firstIndex + numPoints;
        blockSize3 = ((int32_t)check > (int32_t)srcALen) ? (int32_t)check - (int32_t)srcALen : 0;
        blockSize3 = ((int32_t)firstIndex > (int32_t)srcALen - 1) ? blockSize3 - (int32_t)firstIndex + (int32_t)srcALen : blockSize3;
        blockSize1 = (((int32_t) srcBLen - 1) - (int32_t) firstIndex);
        blockSize1 = (blockSize1 > 0) ? ((check > (srcBLen - 1u)) ? blockSize1 :
                                         (int32_t) numPoints) : 0;
        blockSize2 = (int32_t) check - ((blockSize3 + blockSize1) +
                                        (int32_t) firstIndex);
        blockSize2 = (blockSize2 > 0) ? blockSize2 : 0;

        /* conv(x,y) at n = x[n] * y[0] + x[n-1] * y[1] + x[n-2] * y[2] + ...+ x[n-N+1] * y[N -1] */
        /* The function is internally
         * divided into three stages according to the number of multiplications that has to be
         * taken place between inputA samples and inputB samples. In the first stage of the
         * algorithm, the multiplications increase by one for every iteration.
         * In the second stage of the algorithm, srcBLen number of multiplications are done.
         * In the third stage of the algorithm, the multiplications decrease by one
         * for every iteration. */

        /* Set the output pointer to point to the firstIndex
         * of the output sample to be calculated. */
        pOut = pDst + firstIndex;

        /* --------------------------
         * Initializations of stage1
         * -------------------------*/

        /* sum = x[0] * y[0]
         * sum = x[0] * y[1] + x[1] * y[0]
         * ....
         * sum = x[0] * y[srcBlen - 1] + x[1] * y[srcBlen - 2] +...+ x[srcBLen - 1] * y[0]
         */

        /* In this stage the MAC operations are increased by 1 for every iteration.
           The count variable holds the number of MAC operations performed.
           Since the partial convolution starts from firstIndex
           Number of Macs to be performed is firstIndex + 1 */
        count = 1u + firstIndex;

        /* Working pointer of inputA */
        px = pIn1;

        /* Working pointer of inputB */
        pSrc2 = pIn2 + firstIndex;
        py = pSrc2;

        /* ------------------------
         * Stage1 process
         * ----------------------*/

        /* The first loop starts here */
        while(blockSize1 > 0)
        {
            /* Accumulator is made zero for every iteration */
            sum = 0;

            /* Apply loop unrolling and compute 4 MACs simultaneously. */
            k = count >> 2u;

            /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
             ** a second loop below computes MACs for the remaining 1 to 3 samples. */
            while(k > 0u)
            {
                /* x[0] * y[srcBLen - 1] */
                sum += (q63_t) * px++ * (*py--);
                /* x[1] * y[srcBLen - 2] */
                sum += (q63_t) * px++ * (*py--);
                /* x[2] * y[srcBLen - 3] */
                sum += (q63_t) * px++ * (*py--);
                /* x[3] * y[srcBLen - 4] */
                sum += (q63_t) * px++ * (*py--);

                /* Decrement the loop counter */
                k--;
            }

            /* If the count is not a multiple of 4, compute any remaining MACs here.
             ** No loop unrolling is used. */
            k = count % 0x4u;

            while(k > 0u)
            {
                /* Perform the multiply-accumulate */
                sum += (q63_t) * px++ * (*py--);

                /* Decrement the loop counter */
                k--;
            }

            /* Store the result in the accumulator in the destination buffer. */
            *pOut++ = (q31_t)(sum >> 31);

            /* Update the inputA and inputB pointers for next MAC calculation */
            py = ++pSrc2;
            px = pIn1;

            /* Increment the MAC count */
            count++;

            /* Decrement the loop counter */
            blockSize1--;
        }

        /* --------------------------
         * Initializations of stage2
         * ------------------------*/

        /* sum = x[0] * y[srcBLen-1] + x[1] * y[srcBLen-2] +...+ x[srcBLen-1] * y[0]
         * sum = x[1] * y[srcBLen-1] + x[2] * y[srcBLen-2] +...+ x[srcBLen] * y[0]
         * ....
         * sum = x[srcALen-srcBLen-2] * y[srcBLen-1] + x[srcALen] * y[srcBLen-2] +...+ x[srcALen-1] * y[0]
         */

        /* Working pointer of inputA */
        if((int32_t)firstIndex - (int32_t)srcBLen + 1 > 0)
        {
            px = pIn1 + firstIndex - srcBLen + 1;
        }
        else
        {
            px = pIn1;
        }

        /* Working pointer of inputB */
        pSrc2 = pIn2 + (srcBLen - 1u);
        py = pSrc2;

        /* count is index by which the pointer pIn1 to be incremented */
        count = 0u;

        /* -------------------
         * Stage2 process
         * ------------------*/

        /* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed.
         * So, to loop unroll over blockSize2,
         * srcBLen should be greater than or equal to 4 */
        if(srcBLen >= 4u)
        {
            /* Loop unroll over blkCnt */

            blkCnt = blockSize2 / 3;
            while(blkCnt > 0u)
            {
                /* Set all accumulators to zero */
                acc0 = 0;
                acc1 = 0;
                acc2 = 0;

                /* read x[0], x[1] samples */
                x0 = *(px++);
                x1 = *(px++);

                /* Apply loop unrolling and compute 3 MACs simultaneously. */
                k = srcBLen / 3;

                /* First part of the processing with loop unrolling.  Compute 3 MACs at a time.
                 ** a second loop below computes MACs for the remaining 1 to 2 samples. */
                do
                {
                    /* Read y[srcBLen - 1] sample */
                    c0 = *(py);

                    /* Read x[2] sample */
                    x2 = *(px);

                    /* Perform the multiply-accumulates */
                    /* acc0 +=  x[0] * y[srcBLen - 1] */
                    acc0 += (q63_t) x0 * c0;
                    /* acc1 +=  x[1] * y[srcBLen - 1] */
                    acc1 += (q63_t) x1 * c0;
                    /* acc2 +=  x[2] * y[srcBLen - 1] */
                    acc2 += (q63_t) x2 * c0;

                    /* Read y[srcBLen - 2] sample */
                    c0 = *(py - 1u);

                    /* Read x[3] sample */
                    x0 = *(px + 1u);

                    /* Perform the multiply-accumulate */
                    /* acc0 +=  x[1] * y[srcBLen - 2] */
                    acc0 += (q63_t) x1 * c0;
                    /* acc1 +=  x[2] * y[srcBLen - 2] */
                    acc1 += (q63_t) x2 * c0;
                    /* acc2 +=  x[3] * y[srcBLen - 2] */
                    acc2 += (q63_t) x0 * c0;

                    /* Read y[srcBLen - 3] sample */
                    c0 = *(py - 2u);

                    /* Read x[4] sample */
                    x1 = *(px + 2u);

                    /* Perform the multiply-accumulates */
                    /* acc0 +=  x[2] * y[srcBLen - 3] */
                    acc0 += (q63_t) x2 * c0;
                    /* acc1 +=  x[3] * y[srcBLen - 2] */
                    acc1 += (q63_t) x0 * c0;
                    /* acc2 +=  x[4] * y[srcBLen - 2] */
                    acc2 += (q63_t) x1 * c0;


                    px += 3u;

                    py -= 3u;

                }
                while(--k);

                /* If the srcBLen is not a multiple of 3, compute any remaining MACs here.
                 ** No loop unrolling is used. */
                k = srcBLen - (3 * (srcBLen / 3));

                while(k > 0u)
                {
                    /* Read y[srcBLen - 5] sample */
                    c0 = *(py--);

                    /* Read x[7] sample */
                    x2 = *(px++);

                    /* Perform the multiply-accumulates */
                    /* acc0 +=  x[4] * y[srcBLen - 5] */
                    acc0 += (q63_t) x0 * c0;
                    /* acc1 +=  x[5] * y[srcBLen - 5] */
                    acc1 += (q63_t) x1 * c0;
                    /* acc2 +=  x[6] * y[srcBLen - 5] */
                    acc2 += (q63_t) x2 * c0;

                    /* Reuse the present samples for the next MAC */
                    x0 = x1;
                    x1 = x2;

                    /* Decrement the loop counter */
                    k--;
                }

                /* Store the result in the accumulator in the destination buffer. */
                *pOut++ = (q31_t)(acc0 >> 31);
                *pOut++ = (q31_t)(acc1 >> 31);
                *pOut++ = (q31_t)(acc2 >> 31);

                /* Increment the pointer pIn1 index, count by 3 */
                count += 3u;

                /* Update the inputA and inputB pointers for next MAC calculation */
                px = pIn1 + count;
                py = pSrc2;

                /* Decrement the loop counter */
                blkCnt--;
            }

            /* If the blockSize2 is not a multiple of 3, compute any remaining output samples here.
             ** No loop unrolling is used. */
            blkCnt = blockSize2 - 3 * (blockSize2 / 3);

            while(blkCnt > 0u)
            {
                /* Accumulator is made zero for every iteration */
                sum = 0;

                /* Apply loop unrolling and compute 4 MACs simultaneously. */
                k = srcBLen >> 2u;

                /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
                 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
                while(k > 0u)
                {
                    /* Perform the multiply-accumulates */
                    sum += (q63_t) * px++ * (*py--);
                    sum += (q63_t) * px++ * (*py--);
                    sum += (q63_t) * px++ * (*py--);
                    sum += (q63_t) * px++ * (*py--);

                    /* Decrement the loop counter */
                    k--;
                }

                /* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
                 ** No loop unrolling is used. */
                k = srcBLen % 0x4u;

                while(k > 0u)
                {
                    /* Perform the multiply-accumulate */
                    sum += (q63_t) * px++ * (*py--);

                    /* Decrement the loop counter */
                    k--;
                }

                /* Store the result in the accumulator in the destination buffer. */
                *pOut++ = (q31_t)(sum >> 31);

                /* Increment the MAC count */
                count++;

                /* Update the inputA and inputB pointers for next MAC calculation */
                px = pIn1 + count;
                py = pSrc2;

                /* Decrement the loop counter */
                blkCnt--;
            }
        }
        else
        {
            /* If the srcBLen is not a multiple of 4,
             * the blockSize2 loop cannot be unrolled by 4 */
            blkCnt = (uint32_t) blockSize2;

            while(blkCnt > 0u)
            {
                /* Accumulator is made zero for every iteration */
                sum = 0;

                /* srcBLen number of MACS should be performed */
                k = srcBLen;

                while(k > 0u)
                {
                    /* Perform the multiply-accumulate */
                    sum += (q63_t) * px++ * (*py--);

                    /* Decrement the loop counter */
                    k--;
                }

                /* Store the result in the accumulator in the destination buffer. */
                *pOut++ = (q31_t)(sum >> 31);

                /* Increment the MAC count */
                count++;

                /* Update the inputA and inputB pointers for next MAC calculation */
                px = pIn1 + count;
                py = pSrc2;

                /* Decrement the loop counter */
                blkCnt--;
            }
        }


        /* --------------------------
         * Initializations of stage3
         * -------------------------*/

        /* sum += x[srcALen-srcBLen+1] * y[srcBLen-1] + x[srcALen-srcBLen+2] * y[srcBLen-2] +...+ x[srcALen-1] * y[1]
         * sum += x[srcALen-srcBLen+2] * y[srcBLen-1] + x[srcALen-srcBLen+3] * y[srcBLen-2] +...+ x[srcALen-1] * y[2]
         * ....
         * sum +=  x[srcALen-2] * y[srcBLen-1] + x[srcALen-1] * y[srcBLen-2]
         * sum +=  x[srcALen-1] * y[srcBLen-1]
         */

        /* In this stage the MAC operations are decreased by 1 for every iteration.
           The blockSize3 variable holds the number of MAC operations performed */
        count = srcBLen - 1u;

        /* Working pointer of inputA */
        pSrc1 = (pIn1 + srcALen) - (srcBLen - 1u);
        px = pSrc1;

        /* Working pointer of inputB */
        pSrc2 = pIn2 + (srcBLen - 1u);
        py = pSrc2;

        /* -------------------
         * Stage3 process
         * ------------------*/

        while(blockSize3 > 0)
        {
            /* Accumulator is made zero for every iteration */
            sum = 0;

            /* Apply loop unrolling and compute 4 MACs simultaneously. */
            k = count >> 2u;

            /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
             ** a second loop below computes MACs for the remaining 1 to 3 samples. */
            while(k > 0u)
            {
                sum += (q63_t) * px++ * (*py--);
                sum += (q63_t) * px++ * (*py--);
                sum += (q63_t) * px++ * (*py--);
                sum += (q63_t) * px++ * (*py--);

                /* Decrement the loop counter */
                k--;
            }

            /* If the blockSize3 is not a multiple of 4, compute any remaining MACs here.
             ** No loop unrolling is used. */
            k = count % 0x4u;

            while(k > 0u)
            {
                /* Perform the multiply-accumulate */
                sum += (q63_t) * px++ * (*py--);

                /* Decrement the loop counter */
                k--;
            }

            /* Store the result in the accumulator in the destination buffer. */
            *pOut++ = (q31_t)(sum >> 31);

            /* Update the inputA and inputB pointers for next MAC calculation */
            px = ++pSrc1;
            py = pSrc2;

            /* Decrement the MAC count */
            count--;

            /* Decrement the loop counter */
            blockSize3--;

        }

        /* set status as ARM_MATH_SUCCESS */
        status = ARM_MATH_SUCCESS;
    }

    /* Return to application */
    return (status);

#else

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

    q31_t *pIn1 = pSrcA;                           /* inputA pointer */
    q31_t *pIn2 = pSrcB;                           /* inputB pointer */
    q63_t sum;                                     /* Accumulator */
    uint32_t i, j;                                 /* loop counters */
    arm_status status;                             /* status of Partial convolution */

    /* Check for range of output samples to be calculated */
    if((firstIndex + numPoints) > ((srcALen + (srcBLen - 1u))))
    {
        /* Set status as ARM_ARGUMENT_ERROR */
        status = ARM_MATH_ARGUMENT_ERROR;
    }
    else
    {
        /* Loop to calculate convolution for output length number of values */
        for(i = firstIndex; i <= (firstIndex + numPoints - 1); i++)
        {
            /* Initialize sum with zero to carry on MAC operations */
            sum = 0;

            /* Loop to perform MAC operations according to convolution equation */
            for(j = 0; j <= i; j++)
            {
                /* Check the array limitations */
                if(((i - j) < srcBLen) && (j < srcALen))
                {
                    /* z[i] += x[i-j] * y[j] */
                    sum += ((q63_t) pIn1[j] * (pIn2[i - j]));
                }
            }

            /* Store the output in the destination buffer */
            pDst[i] = (q31_t)(sum >> 31u);
        }
        /* set status as ARM_SUCCESS as there are no argument errors */
        status = ARM_MATH_SUCCESS;
    }
    return (status);

#endif /*    #ifndef ARM_MATH_CM0_FAMILY      */

}

/**
 * @} end of PartialConv group
 */
