/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_q31_to_q15.c
* Description: Converts the elements of the Q31 vector to Q15 vector
*
* $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 groupSupport
*/
/**
@addtogroup q31_to_x
@{
*/
/**
@brief Converts the elements of the Q31 vector to Q15 vector.
@param[in] pSrc points to the Q31 input vector
@param[out] pDst points to the Q15 output vector
@param[in] blockSize number of samples in each vector
@return none
@par Details
The equation used for the conversion process is:
<pre>
pDst[n] = (q15_t) pSrc[n] >> 16; 0 <= n < blockSize.
</pre>
*/
void arm_q31_to_q15(
const q31_t * pSrc,
q15_t * pDst,
uint32_t blockSize)
{
uint32_t blkCnt; /* Loop counter */
const q31_t *pIn = pSrc; /* Source pointer */
#if defined (ARM_MATH_LOOPUNROLL) && defined (ARM_MATH_DSP)
q31_t in1, in2, in3, in4;
q31_t out1, out2;
#endif
#if defined (ARM_MATH_LOOPUNROLL)
/* Loop unrolling: Compute 4 outputs at a time */
blkCnt = blockSize >> 2U;
while (blkCnt > 0U)
{
/* C = (q15_t) (A >> 16) */
/* Convert from q31 to q15 and store result in destination buffer */
#if defined (ARM_MATH_DSP)
in1 = *pIn++;
in2 = *pIn++;
in3 = *pIn++;
in4 = *pIn++;
/* pack two higher 16-bit values from two 32-bit values */
#ifndef ARM_MATH_BIG_ENDIAN
out1 = __PKHTB(in2, in1, 16);
out2 = __PKHTB(in4, in3, 16);
#else
out1 = __PKHTB(in1, in2, 16);
out2 = __PKHTB(in3, in4, 16);
#endif /* #ifdef ARM_MATH_BIG_ENDIAN */
write_q15x2_ia (&pDst, out1);
write_q15x2_ia (&pDst, out2);
#else
*pDst++ = (q15_t) (*pIn++ >> 16);
*pDst++ = (q15_t) (*pIn++ >> 16);
*pDst++ = (q15_t) (*pIn++ >> 16);
*pDst++ = (q15_t) (*pIn++ >> 16);
#endif /* #if defined (ARM_MATH_DSP) */
/* 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 = (q15_t) (A >> 16) */
/* Convert from q31 to q15 and store result in destination buffer */
*pDst++ = (q15_t) (*pIn++ >> 16);
/* Decrement loop counter */
blkCnt--;
}
}
/**
@} end of q31_to_x group
*/
