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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_scale_q7.c
  4.  * Description:  Multiplies a Q7 vector by a scalar
  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 groupMath
  33.  */
  34.  
  35. /**
  36.  * @addtogroup scale
  37.  * @{
  38.  */
  39.  
  40. /**
  41.  * @brief Multiplies a Q7 vector by a scalar.
  42.  * @param[in]       *pSrc points to the input vector
  43.  * @param[in]       scaleFract fractional portion of the scale value
  44.  * @param[in]       shift number of bits to shift the result by
  45.  * @param[out]      *pDst points to the output vector
  46.  * @param[in]       blockSize number of samples in the vector
  47.  * @return none.
  48.  *
  49.  * <b>Scaling and Overflow Behavior:</b>
  50.  * \par
  51.  * The input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.7 format.
  52.  * These are multiplied to yield a 2.14 intermediate result and this is shifted with saturation to 1.7 format.
  53.  */
  54.  
  55. void arm_scale_q7(
  56.   q7_t * pSrc,
  57.   q7_t scaleFract,
  58.   int8_t shift,
  59.   q7_t * pDst,
  60.   uint32_t blockSize)
  61. {
  62.   int8_t kShift = 7 - shift;                     /* shift to apply after scaling */
  63.   uint32_t blkCnt;                               /* loop counter */
  64.  
  65. #if defined (ARM_MATH_DSP)
  66.  
  67. /* Run the below code for Cortex-M4 and Cortex-M3 */
  68.   q7_t in1, in2, in3, in4, out1, out2, out3, out4;      /* Temporary variables to store input & output */
  69.  
  70.  
  71.   /*loop Unrolling */
  72.   blkCnt = blockSize >> 2U;
  73.  
  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.     /* Reading 4 inputs from memory */
  80.     in1 = *pSrc++;
  81.     in2 = *pSrc++;
  82.     in3 = *pSrc++;
  83.     in4 = *pSrc++;
  84.  
  85.     /* C = A * scale */
  86.     /* Scale the inputs and then store the results in the temporary variables. */
  87.     out1 = (q7_t) (__SSAT(((in1) * scaleFract) >> kShift, 8));
  88.     out2 = (q7_t) (__SSAT(((in2) * scaleFract) >> kShift, 8));
  89.     out3 = (q7_t) (__SSAT(((in3) * scaleFract) >> kShift, 8));
  90.     out4 = (q7_t) (__SSAT(((in4) * scaleFract) >> kShift, 8));
  91.  
  92.     /* Packing the individual outputs into 32bit and storing in
  93.      * destination buffer in single write */
  94.     *__SIMD32(pDst)++ = __PACKq7(out1, out2, out3, out4);
  95.  
  96.     /* Decrement the loop counter */
  97.     blkCnt--;
  98.   }
  99.  
  100.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  101.    ** No loop unrolling is used. */
  102.   blkCnt = blockSize % 0x4U;
  103.  
  104.   while (blkCnt > 0U)
  105.   {
  106.     /* C = A * scale */
  107.     /* Scale the input and then store the result in the destination buffer. */
  108.     *pDst++ = (q7_t) (__SSAT(((*pSrc++) * scaleFract) >> kShift, 8));
  109.  
  110.     /* Decrement the loop counter */
  111.     blkCnt--;
  112.   }
  113.  
  114. #else
  115.  
  116.   /* Run the below code for Cortex-M0 */
  117.  
  118.   /* Initialize blkCnt with number of samples */
  119.   blkCnt = blockSize;
  120.  
  121.   while (blkCnt > 0U)
  122.   {
  123.     /* C = A * scale */
  124.     /* Scale the input and then store the result in the destination buffer. */
  125.     *pDst++ = (q7_t) (__SSAT((((q15_t) * pSrc++ * scaleFract) >> kShift), 8));
  126.  
  127.     /* Decrement the loop counter */
  128.     blkCnt--;
  129.   }
  130.  
  131. #endif /* #if defined (ARM_MATH_DSP) */
  132.  
  133. }
  134.  
  135. /**
  136.  * @} end of scale group
  137.  */
  138.