text: /* ----------------------------------------------------------------------
  * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
  *
  * $Date: 16/10/14 6:01p $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,
  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * 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
   */
  