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/* ----------------------------------------------------------------------    

* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    

*    

* $Date:        19. March 2015

* $Revision:    V.1.4.5

*    

* 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

*  

* Redistribution and use in source and binary forms, with or without

* modification, are permitted provided that the following conditions

* are met:

*   - Redistributions of source code must retain the above copyright

*     notice, this list of conditions and the following disclaimer.

*   - Redistributions in binary form must reproduce the above copyright

*     notice, this list of conditions and the following disclaimer in

*     the documentation and/or other materials provided with the

*     distribution.

*   - Neither the name of ARM LIMITED nor the names of its contributors

*     may be used to endorse or promote products derived from this

*     software without specific prior written permission.

*

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS

* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE

* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,

* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,

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* POSSIBILITY OF SUCH DAMAGE.

* -------------------------------------------------------------------- */

#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.        

 *

 * The functions support in-place computation allowing the source and destination

 * pointers to reference the same memory buffer.

 */

/**        

 * @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 = (shiftBits & 0x80);             /* Sign of shiftBits */

#ifndef ARM_MATH_CM0_FAMILY

  q31_t in1, in2, in3, in4;                      /* Temporary input variables */

  q31_t out1, out2, out3, out4;                  /* Temporary output variables */

  /*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)

    {

      /* C = A  << shiftBits */

      /* Shift the input and then store the results in the destination buffer. */

      in1 = *pSrc;

      in2 = *(pSrc + 1);

      out1 = in1 << shiftBits;

      in3 = *(pSrc + 2);

      out2 = in2 << shiftBits;

      in4 = *(pSrc + 3);

      if(in1 != (out1 >> shiftBits))

        out1 = 0x7FFFFFFF ^ (in1 >> 31);

      if(in2 != (out2 >> shiftBits))

        out2 = 0x7FFFFFFF ^ (in2 >> 31);

      *pDst = out1;

      out3 = in3 << shiftBits;

      *(pDst + 1) = out2;

      out4 = in4 << shiftBits;

      if(in3 != (out3 >> shiftBits))

        out3 = 0x7FFFFFFF ^ (in3 >> 31);

      if(in4 != (out4 >> shiftBits))

        out4 = 0x7FFFFFFF ^ (in4 >> 31);

      *(pDst + 2) = out3;

      *(pDst + 3) = out4;

      /* Update destination pointer to process next sampels */

      pSrc += 4u;

      pDst += 4u;

      /* Decrement the loop counter */

      blkCnt--;

    }

  }

  else

  {

    /* 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 >>  shiftBits */

      /* Shift the input and then store the results in the destination buffer. */

      in1 = *pSrc;

      in2 = *(pSrc + 1);

      in3 = *(pSrc + 2);

      in4 = *(pSrc + 3);

      *pDst = (in1 >> -shiftBits);

      *(pDst + 1) = (in2 >> -shiftBits);

      *(pDst + 2) = (in3 >> -shiftBits);

      *(pDst + 3) = (in4 >> -shiftBits);

      pSrc += 4u;

      pDst += 4u;

      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_FAMILY */

  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        

 */