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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_q31_to_q7.c
  4.  * Description:  Converts the elements of the Q31 vector to Q7 vector
  5.  *
  6.  * $Date:        27. January 2017
  7.  * $Revision:    V.1.5.1
  8.  *
  9.  * Target Processor: Cortex-M cores
  10.  * -------------------------------------------------------------------- */
  11. /*
  12.  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
  13.  *
  14.  * SPDX-License-Identifier: Apache-2.0
  15.  *
  16.  * Licensed under the Apache License, Version 2.0 (the License); you may
  17.  * not use this file except in compliance with the License.
  18.  * You may obtain a copy of the License at
  19.  *
  20.  * www.apache.org/licenses/LICENSE-2.0
  21.  *
  22.  * Unless required by applicable law or agreed to in writing, software
  23.  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  24.  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  25.  * See the License for the specific language governing permissions and
  26.  * limitations under the License.
  27.  */
  28.  
  29. #include "arm_math.h"
  30.  
  31. /**
  32.  * @ingroup groupSupport
  33.  */
  34.  
  35. /**
  36.  * @addtogroup q31_to_x
  37.  * @{
  38.  */
  39.  
  40. /**
  41.  * @brief Converts the elements of the Q31 vector to Q7 vector.
  42.  * @param[in]       *pSrc points to the Q31 input vector
  43.  * @param[out]      *pDst points to the Q7 output vector
  44.  * @param[in]       blockSize length of the input vector
  45.  * @return none.
  46.  *
  47.  * \par Description:
  48.  *
  49.  * The equation used for the conversion process is:
  50.  *
  51.  * <pre>
  52.  *      pDst[n] = (q7_t) pSrc[n] >> 24;   0 <= n < blockSize.
  53.  * </pre>
  54.  *
  55.  */
  56.  
  57.  
  58. void arm_q31_to_q7(
  59.   q31_t * pSrc,
  60.   q7_t * pDst,
  61.   uint32_t blockSize)
  62. {
  63.   q31_t *pIn = pSrc;                             /* Src pointer */
  64.   uint32_t blkCnt;                               /* loop counter */
  65.  
  66. #if defined (ARM_MATH_DSP)
  67.  
  68.   /* Run the below code for Cortex-M4 and Cortex-M3 */
  69.   q31_t in1, in2, in3, in4;
  70.   q7_t out1, out2, out3, out4;
  71.  
  72.   /*loop Unrolling */
  73.   blkCnt = blockSize >> 2U;
  74.  
  75.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  76.    ** a second loop below computes the remaining 1 to 3 samples. */
  77.   while (blkCnt > 0U)
  78.   {
  79.     /* C = (q7_t) A >> 24 */
  80.     /* convert from q31 to q7 and then store the results in the destination buffer */
  81.     in1 = *pIn++;
  82.     in2 = *pIn++;
  83.     in3 = *pIn++;
  84.     in4 = *pIn++;
  85.  
  86.     out1 = (q7_t) (in1 >> 24);
  87.     out2 = (q7_t) (in2 >> 24);
  88.     out3 = (q7_t) (in3 >> 24);
  89.     out4 = (q7_t) (in4 >> 24);
  90.  
  91.     *__SIMD32(pDst)++ = __PACKq7(out1, out2, out3, out4);
  92.  
  93.     /* Decrement the loop counter */
  94.     blkCnt--;
  95.   }
  96.  
  97.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  98.    ** No loop unrolling is used. */
  99.   blkCnt = blockSize % 0x4U;
  100.  
  101. #else
  102.  
  103.   /* Run the below code for Cortex-M0 */
  104.  
  105.   /* Loop over blockSize number of values */
  106.   blkCnt = blockSize;
  107.  
  108. #endif /* #if defined (ARM_MATH_DSP) */
  109.  
  110.   while (blkCnt > 0U)
  111.   {
  112.     /* C = (q7_t) A >> 24 */
  113.     /* convert from q31 to q7 and then store the results in the destination buffer */
  114.     *pDst++ = (q7_t) (*pIn++ >> 24);
  115.  
  116.     /* Decrement the loop counter */
  117.     blkCnt--;
  118.   }
  119.  
  120. }
  121.  
  122. /**
  123.  * @} end of q31_to_x group
  124.  */
  125.