/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_shift_q31.c
* Description: Shifts the elements of a Q31 vector by a specified number of bits
*
* $Date: 27. January 2017
* $Revision: V.1.5.1
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2017 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 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 */
#if defined (ARM_MATH_DSP)
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 /* #if defined (ARM_MATH_DSP) */
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
*/