hardware/arduino/sam/system/CMSIS/CMSIS/DSP_Lib/Source/BasicMathFunctions/arm_shift_q31.c

/* ----------------------------------------------------------------------   
* Copyright (C) 2010 ARM Limited. All rights reserved.   
*   
* $Date:        15. July 2011  
* $Revision: 	V1.0.10  
*   
* Project: 	    CMSIS DSP Library   
* Title:		arm_shift_q31.c   
*   
* Description:	Shifts the elements of a Q31 vector by a specified number of bits.   
*   
* 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 0.0.7  2010/06/10    
*    Misra-C changes done   
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**   
 * @ingroup groupMath   
 */
/**   
 * @defgroup shift Vector Shift   
 *   
 * Shifts the elements of a fixed-point vector by a specified number of bits.   
 * There are separate functions for Q7, Q15, and Q31 data types.   
 * The underlying algorithm used is:   
 *   
 * <pre>   
 *     pDst[n] = pSrc[n] << shift,   0 <= n < blockSize.   
 * </pre>   
 *   
 * If <code>shift</code> is positive then the elements of the vector are shifted to the left.   
 * If <code>shift</code> is negative then the elements of the vector are shifted to the right.   
 */

/**   
 * @addtogroup shift   
 * @{   
 */

/**   
 * @brief  Shifts the elements of a Q31 vector a specified number of bits.   
 * @param[in]  *pSrc points to the input vector   
 * @param[in]  shiftBits number of bits to shift.  A positive value shifts left; a negative value shifts right.   
 * @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 function uses saturating arithmetic.   
 * Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] will be saturated.   
 */

void arm_shift_q31(
  q31_t * pSrc,
  int8_t shiftBits,
  q31_t * pDst,
  uint32_t blockSize)
{
  uint32_t blkCnt;                               /* loop counter */
  uint8_t sign;                                  /* Sign of shiftBits */
  /* Getting the sign of shiftBits */
  sign = (shiftBits & 0x80);


#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 (>> or <<) shiftBits */
    /* Shift the input and then store the results in the destination buffer. */
    *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
      (*pSrc++ >> -shiftBits);
    *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
      (*pSrc++ >> -shiftBits);
    *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
      (*pSrc++ >> -shiftBits);
    *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
      (*pSrc++ >> -shiftBits);

    /* 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 */


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

#endif /* #ifndef ARM_MATH_CM0 */


  while(blkCnt > 0u)
  {
    /* C = A (>> or <<) shiftBits */
    /* Shift the input and then store the result in the destination buffer. */
    *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
      (*pSrc++ >> -shiftBits);

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

}

/**   
 * @} end of shift group   
 */