File content as of revision 1:fdd22bb7aa52:

/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. May 2012
* $Revision:     V1.1.0
*
* Project:         CMSIS DSP Library
* Title:        arm_scale_q31.c
*
* Description:    Multiplies a Q31 vector by a scalar.
*
* 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 groupMath
 */

/**
 * @addtogroup scale
 * @{
 */

/**
 * @brief Multiplies a Q31 vector by a scalar.
 * @param[in]       *pSrc points to the input vector
 * @param[in]       scaleFract fractional portion of the scale value
 * @param[in]       shift number of bits to shift the result by
 * @param[out]      *pDst points to the output vector
 * @param[in]       blockSize number of samples in the vector
 * @return none.
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.31 format.
 * These are multiplied to yield a 2.62 intermediate result and this is shifted with saturation to 1.31 format.
 */

void arm_scale_q31(
  q31_t * pSrc,
  q31_t scaleFract,
  int8_t shift,
  q31_t * pDst,
  uint32_t blockSize)
{
  int8_t kShift = shift + 1;                     /* Shift to apply after scaling */
  int8_t sign = (kShift & 0x80);
  uint32_t blkCnt;                               /* loop counter */
  q31_t in, out;

#ifndef ARM_MATH_CM0

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

  q31_t in1, in2, in3, in4;                      /* temporary input variables */
  q31_t out1, out2, out3, out4;                  /* temporary output variabels */


  /*loop Unrolling */
  blkCnt = blockSize >> 2u;

  if(sign == 0u)
  {
    /* 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 four inputs from source */
      in1 = *pSrc;
      in2 = *(pSrc + 1);
      in3 = *(pSrc + 2);
      in4 = *(pSrc + 3);

      /* multiply input with scaler value */
      in1 = ((q63_t) in1 * scaleFract) >> 32;
      in2 = ((q63_t) in2 * scaleFract) >> 32;
      in3 = ((q63_t) in3 * scaleFract) >> 32;
      in4 = ((q63_t) in4 * scaleFract) >> 32;

      /* apply shifting */
      out1 = in1 << kShift;
      out2 = in2 << kShift;

      /* saturate the results. */
      if(in1 != (out1 >> kShift))
        out1 = 0x7FFFFFFF ^ (in1 >> 31);

      if(in2 != (out2 >> kShift))
        out2 = 0x7FFFFFFF ^ (in2 >> 31);

      out3 = in3 << kShift;
      out4 = in4 << kShift;

      *pDst = out1;
      *(pDst + 1) = out2;

      if(in3 != (out3 >> kShift))
        out3 = 0x7FFFFFFF ^ (in3 >> 31);

      if(in4 != (out4 >> kShift))
        out4 = 0x7FFFFFFF ^ (in4 >> 31);

      /* Store result destination */
      *(pDst + 2) = out3;
      *(pDst + 3) = out4;

      /* Update pointers to process next sampels */
      pSrc += 4u;
      pDst += 4u;

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

  }
  else
  {
    kShift = -kShift;

    /* 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 four inputs from source */
      in1 = *pSrc;
      in2 = *(pSrc + 1);
      in3 = *(pSrc + 2);
      in4 = *(pSrc + 3);

      /* multiply input with scaler value */
      in1 = ((q63_t) in1 * scaleFract) >> 32;
      in2 = ((q63_t) in2 * scaleFract) >> 32;
      in3 = ((q63_t) in3 * scaleFract) >> 32;
      in4 = ((q63_t) in4 * scaleFract) >> 32;

      /* apply shifting */
      out1 = in1 >> kShift;
      out2 = in2 >> kShift;

      out3 = in3 >> kShift;
      out4 = in4 >> kShift;

      /* Store result destination */
      *pDst = out1;
      *(pDst + 1) = out2;

      *(pDst + 2) = out3;
      *(pDst + 3) = out4;

      /* Update pointers to process next sampels */
      pSrc += 4u;
      pDst += 4u;

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

#else

  /* Run the below code for Cortex-M0 */
  if(sign != 0u)
    kShift = -kShift;

  /* Initialize blkCnt with number of samples */
  blkCnt = blockSize;

#endif /* #ifndef ARM_MATH_CM0 */

  while(blkCnt > 0u)
  {
    /* C = A * scale */
    /* Scale the input and then store the result in the destination buffer. */
    in = *pSrc++;
    in = ((q63_t) in * scaleFract) >> 32;

    if(sign == 0)
    {
      out = in << kShift;
      if(in != (out >> kShift))
        out = 0x7FFFFFFF ^ (in >> 31);
    }
    else
    {
      out = in >> kShift;
    }

    *pDst++ = out;

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

/**
 * @} end of scale group
 */