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# arm_shift_q31.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        29. November 2010
    00005 * $Revision:    V1.0.3
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_shift_q31.c
    00009 *
    00010 * Description:  Shifts the elements of a Q31 vector
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.3 2010/11/29
    00015 *    Re-organized the CMSIS folders and updated documentation.
    00016 *
    00017 * Version 1.0.2 2010/11/11
    00018 *    Documentation updated.
    00019 *
    00020 * Version 1.0.1 2010/10/05
    00021 *    Production release and review comments incorporated.
    00022 *
    00023 * Version 1.0.0 2010/09/20
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 0.0.7  2010/06/10
    00027 *    Misra-C changes done
    00028 * -------------------------------------------------------------------- */
    00029
    00030 #include "arm_math.h"
    00031
    00070 void arm_shift_q31(
    00071   q31_t * pSrc,
    00072   int8_t shiftBits,
    00073   q31_t * pDst,
    00074   uint32_t blockSize)
    00075 {
    00076   uint32_t blkCnt;                               /* loop counter */
    00077   uint32_t sign;                                 /* Sign of shiftBits */
    00078
    00079
    00080   /*loop Unrolling */
    00081   blkCnt = blockSize >> 2u;
    00082
    00083   /* Getting the sign of shiftBits */
    00084   sign = (shiftBits & 0x80000000);
    00085
    00086   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00087    ** a second loop below computes the remaining 1 to 3 samples. */
    00088   while(blkCnt > 0u)
    00089   {
    00090     /* C = A (>> or <<) shiftBits */
    00091     /* Shift the input and then store the results in the destination buffer. */
    00092     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00093                              (*pSrc++ >> -shiftBits);
    00094     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00095                              (*pSrc++ >> -shiftBits);
    00096     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00097                              (*pSrc++ >> -shiftBits);
    00098     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00099                              (*pSrc++ >> -shiftBits);
    00100
    00101     /* Decrement the loop counter */
    00102     blkCnt--;
    00103   }
    00104
    00105   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00106    ** No loop unrolling is used. */
    00107   blkCnt = blockSize % 0x4u;
    00108
    00109   while(blkCnt > 0u)
    00110   {
    00111     /* C = A (>> or <<) shiftBits */
    00112     /* Shift the input and then store the result in the destination buffer. */
    00113     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00114                              (*pSrc++ >> -shiftBits);
    00115
    00116     /* Decrement the loop counter */
    00117     blkCnt--;
    00118   }
    00119
    00120 }
    00121

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