hardware/arduino/sam/system/CMSIS/CMSIS/DSP_Lib/Source/BasicMathFunctions/arm_mult_q15.c

/* ----------------------------------------------------------------------   
* Copyright (C) 2010 ARM Limited. All rights reserved.   
*   
* $Date:        15. July 2011  
* $Revision: 	V1.0.10  
*   
* Project: 	    CMSIS DSP Library   
* Title:	    arm_mult_q15.c   
*   
* Description:	Q15 vector multiplication.   
*   
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*  
* 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 0.0.5  2010/04/26    
*    incorporated review comments and updated with latest CMSIS layer   
*   
* Version 0.0.3  2010/03/10    
*    Initial version   
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**   
 * @ingroup groupMath   
 */

/**   
 * @addtogroup BasicMult   
 * @{   
 */


/**   
 * @brief           Q15 vector multiplication   
 * @param[in]       *pSrcA points to the first input vector   
 * @param[in]       *pSrcB points to the second input vector   
 * @param[out]      *pDst points to the output vector   
 * @param[in]       blockSize number of samples in each vector   
 * @return none.   
 *   
 * <b>Scaling and Overflow Behavior:</b>   
 * \par   
 * The function uses saturating arithmetic.   
 * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.   
 */

void arm_mult_q15(
  q15_t * pSrcA,
  q15_t * pSrcB,
  q15_t * pDst,
  uint32_t blockSize)
{
  uint32_t blkCnt;                               /* loop counters */

#ifndef ARM_MATH_CM0

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

  /* 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)
  {
    /* C = A * B */
    /* Multiply the inputs and store the result in the destination buffer */
    *pDst++ = (q15_t) __SSAT((((q31_t) (*pSrcA++) * (*pSrcB++)) >> 15), 16);
    *pDst++ = (q15_t) __SSAT((((q31_t) (*pSrcA++) * (*pSrcB++)) >> 15), 16);
    *pDst++ = (q15_t) __SSAT((((q31_t) (*pSrcA++) * (*pSrcB++)) >> 15), 16);
    *pDst++ = (q15_t) __SSAT((((q31_t) (*pSrcA++) * (*pSrcB++)) >> 15), 16);

    /* Decrement the blockSize 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 */

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

#endif /* #ifndef ARM_MATH_CM0 */


  while(blkCnt > 0u)
  {
    /* C = A * B */
    /* Multiply the inputs and store the result in the destination buffer */
    *pDst++ = (q15_t) __SSAT((((q31_t) (*pSrcA++) * (*pSrcB++)) >> 15), 16);

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

/**   
 * @} end of BasicMult group   
 */