text: /*-----------------------------------------------------------------------------    
  * Copyright (C) 2010 ARM Limited. All rights reserved.    
  *    
  * $Date:        15. February 2012  
  * $Revision: 	V1.1.0  
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:		arm_fir_interpolate_q15.c    
  *    
  * Description:	Q15 FIR interpolation.    
  *    
  * 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 1.0.10 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 FIR_Interpolate    
   * @{    
   */
  
  /**    
   * @brief Processing function for the Q15 FIR interpolator.    
   * @param[in] *S        points to an instance of the Q15 FIR interpolator 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 input samples to process per call.    
   * @return none.    
   *    
   * <b>Scaling and Overflow Behavior:</b>    
   * \par    
   * The function is implemented using a 64-bit internal accumulator.    
   * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.    
   * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.    
   * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.    
   * After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.    
   * Lastly, the accumulator is saturated to yield a result in 1.15 format.    
   */
  
  #ifndef ARM_MATH_CM0
  
    /* Run the below code for Cortex-M4 and Cortex-M3 */
  
  void arm_fir_interpolate_q15(
    const arm_fir_interpolate_instance_q15 * S,
    q15_t * pSrc,
    q15_t * pDst,
    uint32_t blockSize)
  {
    q15_t *pState = S->pState;                     /* State pointer                                            */
    q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer                                      */
    q15_t *pStateCurnt;                            /* Points to the current sample of the state                */
    q15_t *ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers     */
    q63_t sum0;                                    /* Accumulators                                             */
    q15_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */
    uint32_t i, blkCnt, j, tapCnt;                 /* Loop counters                                            */
    uint16_t phaseLen = S->phaseLength;            /* Length of each polyphase filter component */
    uint32_t blkCntN2;
    q63_t acc0, acc1;
    q15_t x1;
  
    /* S->pState buffer contains previous frame (phaseLen - 1) samples */
    /* pStateCurnt points to the location where the new input data should be written */
    pStateCurnt = S->pState + ((q31_t) phaseLen - 1);
  
    /* Initialise  blkCnt */
    blkCnt = blockSize / 2;
    blkCntN2 = blockSize - (2 * blkCnt);
  
    /* Samples loop unrolled by 2 */
    while(blkCnt > 0u)
    {
      /* Copy new input sample into the state buffer */
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
  
      /* Address modifier index of coefficient buffer */
      j = 1u;
  
      /* Loop over the Interpolation factor. */
      i = (S->L);
  
      while(i > 0u)
      {
        /* Set accumulator to zero */
        acc0 = 0;
        acc1 = 0;
  
        /* Initialize state pointer */
        ptr1 = pState;
  
        /* Initialize coefficient pointer */
        ptr2 = pCoeffs + (S->L - j);
  
        /* Loop over the polyPhase length. Unroll by a factor of 4.        
         ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
        tapCnt = phaseLen >> 2u;
  
        x0 = *(ptr1++);
  
        while(tapCnt > 0u)
        {
  
          /* Read the input sample */
          x1 = *(ptr1++);
  
          /* Read the coefficient */
          c0 = *(ptr2);
  
          /* Perform the multiply-accumulate */
          acc0 += (q63_t) x0 *c0;
          acc1 += (q63_t) x1 *c0;
  
  
          /* Read the coefficient */
          c0 = *(ptr2 + S->L);
  
          /* Read the input sample */
          x0 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          acc0 += (q63_t) x1 *c0;
          acc1 += (q63_t) x0 *c0;
  
  
          /* Read the coefficient */
          c0 = *(ptr2 + S->L * 2);
  
          /* Read the input sample */
          x1 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          acc0 += (q63_t) x0 *c0;
          acc1 += (q63_t) x1 *c0;
  
          /* Read the coefficient */
          c0 = *(ptr2 + S->L * 3);
  
          /* Read the input sample */
          x0 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          acc0 += (q63_t) x1 *c0;
          acc1 += (q63_t) x0 *c0;
  
  
          /* Upsampling is done by stuffing L-1 zeros between each sample.        
           * So instead of multiplying zeros with coefficients,        
           * Increment the coefficient pointer by interpolation factor times. */
          ptr2 += 4 * S->L;
  
          /* Decrement the loop counter */
          tapCnt--;
        }
  
        /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
        tapCnt = phaseLen % 0x4u;
  
        while(tapCnt > 0u)
        {
  
          /* Read the input sample */
          x1 = *(ptr1++);
  
          /* Read the coefficient */
          c0 = *(ptr2);
  
          /* Perform the multiply-accumulate */
          acc0 += (q63_t) x0 *c0;
          acc1 += (q63_t) x1 *c0;
  
          /* Increment the coefficient pointer by interpolation factor times. */
          ptr2 += S->L;
  
          /* update states for next sample processing */
          x0 = x1;
  
          /* Decrement the loop counter */
          tapCnt--;
        }
  
        /* The result is in the accumulator, store in the destination buffer. */
        *pDst = (q15_t) (__SSAT((acc0 >> 15), 16));
        *(pDst + S->L) = (q15_t) (__SSAT((acc1 >> 15), 16));
  
        pDst++;
  
        /* Increment the address modifier index of coefficient buffer */
        j++;
  
        /* Decrement the loop counter */
        i--;
      }
  
      /* Advance the state pointer by 1        
       * to process the next group of interpolation factor number samples */
      pState = pState + 2;
  
      pDst += S->L;
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
    /* If the blockSize is not a multiple of 2, compute any remaining output samples here.        
     ** No loop unrolling is used. */
    blkCnt = blkCntN2;
  
    /* Loop over the blockSize. */
    while(blkCnt > 0u)
    {
      /* Copy new input sample into the state buffer */
      *pStateCurnt++ = *pSrc++;
  
      /* Address modifier index of coefficient buffer */
      j = 1u;
  
      /* Loop over the Interpolation factor. */
      i = S->L;
      while(i > 0u)
      {
        /* Set accumulator to zero */
        sum0 = 0;
  
        /* Initialize state pointer */
        ptr1 = pState;
  
        /* Initialize coefficient pointer */
        ptr2 = pCoeffs + (S->L - j);
  
        /* Loop over the polyPhase length. Unroll by a factor of 4.        
         ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
        tapCnt = phaseLen >> 2;
        while(tapCnt > 0u)
        {
  
          /* Read the coefficient */
          c0 = *(ptr2);
  
          /* Upsampling is done by stuffing L-1 zeros between each sample.        
           * So instead of multiplying zeros with coefficients,        
           * Increment the coefficient pointer by interpolation factor times. */
          ptr2 += S->L;
  
          /* Read the input sample */
          x0 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          sum0 += (q63_t) x0 *c0;
  
          /* Read the coefficient */
          c0 = *(ptr2);
  
          /* Increment the coefficient pointer by interpolation factor times. */
          ptr2 += S->L;
  
          /* Read the input sample */
          x0 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          sum0 += (q63_t) x0 *c0;
  
          /* Read the coefficient */
          c0 = *(ptr2);
  
          /* Increment the coefficient pointer by interpolation factor times. */
          ptr2 += S->L;
  
          /* Read the input sample */
          x0 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          sum0 += (q63_t) x0 *c0;
  
          /* Read the coefficient */
          c0 = *(ptr2);
  
          /* Increment the coefficient pointer by interpolation factor times. */
          ptr2 += S->L;
  
          /* Read the input sample */
          x0 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          sum0 += (q63_t) x0 *c0;
  
          /* Decrement the loop counter */
          tapCnt--;
        }
  
        /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
        tapCnt = phaseLen & 0x3u;
  
        while(tapCnt > 0u)
        {
          /* Read the coefficient */
          c0 = *(ptr2);
  
          /* Increment the coefficient pointer by interpolation factor times. */
          ptr2 += S->L;
  
          /* Read the input sample */
          x0 = *(ptr1++);
  
          /* Perform the multiply-accumulate */
          sum0 += (q63_t) x0 *c0;
  
          /* Decrement the loop counter */
          tapCnt--;
        }
  
        /* The result is in the accumulator, store in the destination buffer. */
        *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));
  
        j++;
  
        /* Decrement the loop counter */
        i--;
      }
  
      /* Advance the state pointer by 1        
       * to process the next group of interpolation factor number samples */
      pState = pState + 1;
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
  
    /* Processing is complete.    
     ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.    
     ** This prepares the state buffer for the next function call. */
  
    /* Points to the start of the state buffer */
    pStateCurnt = S->pState;
  
    i = ((uint32_t) phaseLen - 1u) >> 2u;
  
    /* copy data */
    while(i > 0u)
    {
  #ifndef UNALIGNED_SUPPORT_DISABLE
  
      *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
      *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
  
  #else
  
      *pStateCurnt++ = *pState++;
  	*pStateCurnt++ = *pState++;
  	*pStateCurnt++ = *pState++;
  	*pStateCurnt++ = *pState++;
  	
  #endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/
  	
  	/* Decrement the loop counter */
      i--;
    }
  
    i = ((uint32_t) phaseLen - 1u) % 0x04u;
  
    while(i > 0u)
    {
      *pStateCurnt++ = *pState++;
  
      /* Decrement the loop counter */
      i--;
    }
  }
  
  #else
  
    /* Run the below code for Cortex-M0 */
  
  void arm_fir_interpolate_q15(
    const arm_fir_interpolate_instance_q15 * S,
    q15_t * pSrc,
    q15_t * pDst,
    uint32_t blockSize)
  {
    q15_t *pState = S->pState;                     /* State pointer                                            */
    q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer                                      */
    q15_t *pStateCurnt;                            /* Points to the current sample of the state                */
    q15_t *ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers     */
    q63_t sum;                                     /* Accumulator */
    q15_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */
    uint32_t i, blkCnt, tapCnt;                    /* Loop counters                                            */
    uint16_t phaseLen = S->phaseLength;            /* Length of each polyphase filter component */
  
  
    /* S->pState buffer contains previous frame (phaseLen - 1) samples */
    /* pStateCurnt points to the location where the new input data should be written */
    pStateCurnt = S->pState + (phaseLen - 1u);
  
    /* Total number of intput samples */
    blkCnt = blockSize;
  
    /* Loop over the blockSize. */
    while(blkCnt > 0u)
    {
      /* Copy new input sample into the state buffer */
      *pStateCurnt++ = *pSrc++;
  
      /* Loop over the Interpolation factor. */
      i = S->L;
  
      while(i > 0u)
      {
        /* Set accumulator to zero */
        sum = 0;
  
        /* Initialize state pointer */
        ptr1 = pState;
  
        /* Initialize coefficient pointer */
        ptr2 = pCoeffs + (i - 1u);
  
        /* Loop over the polyPhase length */
        tapCnt = (uint32_t) phaseLen;
  
        while(tapCnt > 0u)
        {
          /* Read the coefficient */
          c0 = *ptr2;
  
          /* Increment the coefficient pointer by interpolation factor times. */
          ptr2 += S->L;
  
          /* Read the input sample */
          x0 = *ptr1++;
  
          /* Perform the multiply-accumulate */
          sum += ((q31_t) x0 * c0);
  
          /* Decrement the loop counter */
          tapCnt--;
        }
  
        /* Store the result after converting to 1.15 format in the destination buffer */
        *pDst++ = (q15_t) (__SSAT((sum >> 15), 16));
  
        /* Decrement the loop counter */
        i--;
      }
  
      /* Advance the state pointer by 1           
       * to process the next group of interpolation factor number samples */
      pState = pState + 1;
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
    /* Processing is complete.         
     ** Now copy the last phaseLen - 1 samples to the start of the state buffer.       
     ** This prepares the state buffer for the next function call. */
  
    /* Points to the start of the state buffer */
    pStateCurnt = S->pState;
  
    i = (uint32_t) phaseLen - 1u;
  
    while(i > 0u)
    {
      *pStateCurnt++ = *pState++;
  
      /* Decrement the loop counter */
      i--;
    }
  
  }
  
  #endif /*   #ifndef ARM_MATH_CM0 */
  
  
   /**    
    * @} end of FIR_Interpolate group    
    */
  