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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_q15_to_q7.c
* Description: Converts the elements of the Q15 vector to Q7 vector
*
* $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 groupSupport
*/
/**
* @addtogroup q15_to_x
* @{
*/
/**
* @brief Converts the elements of the Q15 vector to Q7 vector.
* @param[in] *pSrc points to the Q15 input vector
* @param[out] *pDst points to the Q7 output vector
* @param[in] blockSize length of the input vector
* @return none.
*
* \par Description:
*
* The equation used for the conversion process is:
*
* <pre>
* pDst[n] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize.
* </pre>
*
*/
void arm_q15_to_q7(
q15_t * pSrc,
q7_t * pDst,
uint32_t blockSize)
{
q15_t *pIn = pSrc; /* Src pointer */
uint32_t blkCnt; /* loop counter */
#if defined (ARM_MATH_DSP)
/* Run the below code for Cortex-M4 and Cortex-M3 */
q31_t in1, in2;
q31_t out1, out2;
/*loop Unrolling */
blkCnt = blockSize >> 2U;
/* 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 = (q7_t) A >> 8 */
/* convert from q15 to q7 and then store the results in the destination buffer */
in1 = *__SIMD32(pIn)++;
in2 = *__SIMD32(pIn)++;
#ifndef ARM_MATH_BIG_ENDIAN
out1 = __PKHTB(in2, in1, 16);
out2 = __PKHBT(in2, in1, 16);
#else
out1 = __PKHTB(in1, in2, 16);
out2 = __PKHBT(in1, in2, 16);
#endif // #ifndef ARM_MATH_BIG_ENDIAN
/* rotate packed value by 24 */
out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);
/* anding with 0xff00ff00 to get two 8 bit values */
out1 = out1 & 0xFF00FF00;
/* anding with 0x00ff00ff to get two 8 bit values */
out2 = out2 & 0x00FF00FF;
/* oring two values(contains two 8 bit values) to get four packed 8 bit values */
out1 = out1 | out2;
/* store 4 samples at a time to destiantion buffer */
*__SIMD32(pDst)++ = out1;
/* Decrement the loop counter */
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 */
/* Loop over blockSize number of values */
blkCnt = blockSize;
#endif /* #if defined (ARM_MATH_DSP) */
while (blkCnt > 0U)
{
/* C = (q7_t) A >> 8 */
/* convert from q15 to q7 and then store the results in the destination buffer */
*pDst++ = (q7_t) (*pIn++ >> 8);
/* Decrement the loop counter */
blkCnt--;
}
}
/**
* @} end of q15_to_x group
*/
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