/* ----------------------------------------------------------------------
* 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
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*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
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*   - 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
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* -------------------------------------------------------------------- */

#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
 */
