arm_scale_q31.c

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/* ----------------------------------------------------------------------      
* Copyright (C) 2011 ARM Limited. All rights reserved. 
*      
* $Date:        15. December 2011   
* $Revision:    V2.0.0  
*      
* Project:      Cortex-R DSP Library 
* Title:        arm_scale_q31.c      
*      
* Description:  Multiplies a Q31 vector by a scalar.      
*      
* Target Processor:          Cortex-R4/R5
*
* Version 1.0.0 2011/03/08
*     Alpha release.
*
* Version 1.0.1 2011/09/30
*     Beta release.
*
* Version 2.0.0 2011/12/15
*     Final release. 
* 
* -------------------------------------------------------------------- */     
#include "arm_math.h"     
     
void arm_scale_q31(     
  q31_t * pSrc,     
  q31_t scaleFract,     
  int8_t shift,     
  q31_t * pDst,     
  uint32_t blockSize)     
{     
  int8_t kShift = 31 - shift;                    /* Shift to apply after scaling */ 
  
  uint32_t blkCnt;                               /* loop counter */     
     
     
  /*loop Unrolling */     
  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 four inputs from source */  
    *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
    *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
    *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
    *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
 
  
    /* 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;     
     
  while(blkCnt > 0u)     
  {     
    /* C = A * scale */     
    /* Scale the input and then store the result in the destination buffer. */     
    *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
  
    /* Decrement the loop counter */     
    blkCnt--;     
  }     
}