text: /* ----------------------------------------------------------------------    
  * Copyright (C) 2010 ARM Limited. All rights reserved.    
  *    
  * $Date: 14/06/07 1:57a $Revision: 	V1.1.0  
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:		arm_conv_partial_q31.c    
  *    
  * Description:	Partial convolution of Q31 sequences.    
  *    
  * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  *  
  * Version 1.1.0 2012/02/15 
  *    Updated with more optimizations, bug fixes and minor API changes.  
  *  
  * Version 1.0.11 2011/10/18  
  *    Bug Fix in conv, correlation, partial convolution.  
  * 
  * Version 1.0.10 2011/7/15  
  *    Big Endian support added and Merged M0 and M3/M4 Source code.   
  *    
  * Version 1.0.3 2010/11/29   
  *    Re-organized the CMSIS folders and updated documentation.    
  *     
  * Version 1.0.2 2010/11/11    
  *    Documentation updated.     
  *    
  * Version 1.0.1 2010/10/05     
  *    Production release and review comments incorporated.    
  *    
  * Version 1.0.0 2010/09/20     
  *    Production release and review comments incorporated    
  *    
  * Version 0.0.7  2010/06/10     
  *    Misra-C changes done    
  *    
  * -------------------------------------------------------------------- */
  
  #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
  
    /* 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);
      blockSize3 = (blockSize3 > 0) ? blockSize3 : 0;
      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 */
      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      */
  
  }
  
  /**    
   * @} end of PartialConv group    
   */
  