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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_shift_q31.c
* Description: Shifts the elements of a Q31 vector by a specified number of bits
*
* $Date: 18. March 2019
* $Revision: V1.6.0
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "arm_math.h"
/**
@ingroup groupMath
*/
/**
@defgroup BasicShift 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 BasicShift
@{
*/
/**
@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
@par Scaling and Overflow Behavior
The function uses saturating arithmetic.
Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] are saturated.
*/
void arm_shift_q31(
const 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 */
#if defined (ARM_MATH_LOOPUNROLL)
q31_t in, out; /* Temporary variables */
/* Loop unrolling: Compute 4 outputs at a time */
blkCnt = blockSize >> 2U;
/* If the shift value is positive then do right shift else left shift */
if (sign == 0U)
{
while (blkCnt > 0U)
{
/* C = A << shiftBits */
/* Shift input and store result in destination buffer. */
in = *pSrc++;
out = in << shiftBits;
if (in != (out >> shiftBits))
out = 0x7FFFFFFF ^ (in >> 31);
*pDst++ = out;
in = *pSrc++;
out = in << shiftBits;
if (in != (out >> shiftBits))
out = 0x7FFFFFFF ^ (in >> 31);
*pDst++ = out;
in = *pSrc++;
out = in << shiftBits;
if (in != (out >> shiftBits))
out = 0x7FFFFFFF ^ (in >> 31);
*pDst++ = out;
in = *pSrc++;
out = in << shiftBits;
if (in != (out >> shiftBits))
out = 0x7FFFFFFF ^ (in >> 31);
*pDst++ = out;
/* Decrement loop counter */
blkCnt--;
}
}
else
{
while (blkCnt > 0U)
{
/* C = A >> shiftBits */
/* Shift input and store results in destination buffer. */
*pDst++ = (*pSrc++ >> -shiftBits);
*pDst++ = (*pSrc++ >> -shiftBits);
*pDst++ = (*pSrc++ >> -shiftBits);
*pDst++ = (*pSrc++ >> -shiftBits);
/* Decrement loop counter */
blkCnt--;
}
}
/* Loop unrolling: Compute remaining outputs */
blkCnt = blockSize % 0x4U;
#else
/* Initialize blkCnt with number of samples */
blkCnt = blockSize;
#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
/* If the shift value is positive then do right shift else left shift */
if (sign == 0U)
{
while (blkCnt > 0U)
{
/* C = A << shiftBits */
/* Shift input and store result in destination buffer. */
*pDst++ = clip_q63_to_q31((q63_t) *pSrc++ << shiftBits);
/* Decrement loop counter */
blkCnt--;
}
}
else
{
while (blkCnt > 0U)
{
/* C = A >> shiftBits */
/* Shift input and store result in destination buffer. */
*pDst++ = (*pSrc++ >> -shiftBits);
/* Decrement loop counter */
blkCnt--;
}
}
}
/**
@} end of BasicShift group
*/
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