/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_scale_q15.c
* Description: Multiplies a Q15 vector by a scalar
*
* $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 BasicScale
@{
*/
/**
@brief Multiplies a Q15 vector by a scalar.
@param[in] pSrc points to the input vector
@param[in] scaleFract fractional portion of the scale value
@param[in] shift number of bits to shift the result by
@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 input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.15 format.
These are multiplied to yield a 2.30 intermediate result and this is shifted with saturation to 1.15 format.
*/
void arm_scale_q15(
const q15_t *pSrc,
q15_t scaleFract,
int8_t shift,
q15_t *pDst,
uint32_t blockSize)
{
uint32_t blkCnt; /* Loop counter */
int8_t kShift = 15 - shift; /* Shift to apply after scaling */
#if defined (ARM_MATH_LOOPUNROLL)
#if defined (ARM_MATH_DSP)
q31_t inA1, inA2;
q31_t out1, out2, out3, out4; /* Temporary output variables */
q15_t in1, in2, in3, in4; /* Temporary input variables */
#endif
#endif
#if defined (ARM_MATH_LOOPUNROLL)
/* Loop unrolling: Compute 4 outputs at a time */
blkCnt = blockSize >> 2U;
while (blkCnt > 0U)
{
/* C = A * scale */
#if defined (ARM_MATH_DSP)
/* read 2 times 2 samples at a time from source */
inA1 = read_q15x2_ia ((q15_t **) &pSrc);
inA2 = read_q15x2_ia ((q15_t **) &pSrc);
/* Scale inputs and store result in temporary variables
* in single cycle by packing the outputs */
out1 = (q31_t) ((q15_t) (inA1 >> 16) * scaleFract);
out2 = (q31_t) ((q15_t) (inA1 ) * scaleFract);
out3 = (q31_t) ((q15_t) (inA2 >> 16) * scaleFract);
out4 = (q31_t) ((q15_t) (inA2 ) * scaleFract);
/* apply shifting */
out1 = out1 >> kShift;
out2 = out2 >> kShift;
out3 = out3 >> kShift;
out4 = out4 >> kShift;
/* saturate the output */
in1 = (q15_t) (__SSAT(out1, 16));
in2 = (q15_t) (__SSAT(out2, 16));
in3 = (q15_t) (__SSAT(out3, 16));
in4 = (q15_t) (__SSAT(out4, 16));
/* store result to destination */
write_q15x2_ia (&pDst, __PKHBT(in2, in1, 16));
write_q15x2_ia (&pDst, __PKHBT(in4, in3, 16));
#else
*pDst++ = (q15_t) (__SSAT(((q31_t) *pSrc++ * scaleFract) >> kShift, 16));
*pDst++ = (q15_t) (__SSAT(((q31_t) *pSrc++ * scaleFract) >> kShift, 16));
*pDst++ = (q15_t) (__SSAT(((q31_t) *pSrc++ * scaleFract) >> kShift, 16));
*pDst++ = (q15_t) (__SSAT(((q31_t) *pSrc++ * scaleFract) >> kShift, 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 * scale */
/* Scale input and store result in destination buffer. */
*pDst++ = (q15_t) (__SSAT(((q31_t) *pSrc++ * scaleFract) >> kShift, 16));
/* Decrement loop counter */
blkCnt--;
}
}
/**
@} end of BasicScale group
*/
