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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_sub_q15.c
* Description: Q15 vector subtraction
*
* $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
*/
/**
@addtogroup BasicSub
@{
*/
/**
@brief Q15 vector subtraction.
@param[in] pSrcA points to the first input vector
@param[in] pSrcB points to the second input vector
@param[out] pDst points to the output vector
@param[in] blockSize number of samples in each vector
@return none
@par Scaling and Overflow Behavior
The function uses saturating arithmetic.
Results outside of the allowable Q15 range [0x8000 0x7FFF] are saturated.
*/
void arm_sub_q15(
const q15_t * pSrcA,
const q15_t * pSrcB,
q15_t * pDst,
uint32_t blockSize)
{
uint32_t blkCnt; /* Loop counter */
#if defined (ARM_MATH_LOOPUNROLL)
#if defined (ARM_MATH_DSP)
q31_t inA1, inA2;
q31_t inB1, inB2;
#endif
/* Loop unrolling: Compute 4 outputs at a time */
blkCnt = blockSize >> 2U;
while (blkCnt > 0U)
{
/* C = A - B */
#if defined (ARM_MATH_DSP)
/* read 2 times 2 samples at a time from sourceA */
inA1 = read_q15x2_ia ((q15_t **) &pSrcA);
inA2 = read_q15x2_ia ((q15_t **) &pSrcA);
/* read 2 times 2 samples at a time from sourceB */
inB1 = read_q15x2_ia ((q15_t **) &pSrcB);
inB2 = read_q15x2_ia ((q15_t **) &pSrcB);
/* Subtract and store 2 times 2 samples at a time */
write_q15x2_ia (&pDst, __QSUB16(inA1, inB1));
write_q15x2_ia (&pDst, __QSUB16(inA2, inB2));
#else
*pDst++ = (q15_t) __SSAT(((q31_t) *pSrcA++ - *pSrcB++), 16);
*pDst++ = (q15_t) __SSAT(((q31_t) *pSrcA++ - *pSrcB++), 16);
*pDst++ = (q15_t) __SSAT(((q31_t) *pSrcA++ - *pSrcB++), 16);
*pDst++ = (q15_t) __SSAT(((q31_t) *pSrcA++ - *pSrcB++), 16);
#endif
/* 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) */
while (blkCnt > 0U)
{
/* C = A - B */
/* Subtract and store result in destination buffer. */
#if defined (ARM_MATH_DSP)
*pDst++ = (q15_t) __QSUB16(*pSrcA++, *pSrcB++);
#else
*pDst++ = (q15_t) __SSAT(((q31_t) *pSrcA++ - *pSrcB++), 16);
#endif
/* Decrement loop counter */
blkCnt--;
}
}
/**
@} end of BasicSub group
*/
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