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# arm_scale_q15.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        29. November 2010
    00005 * $Revision:    V1.0.3
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_scale_q15.c
    00009 *
    00010 * Description:  Multiplies a Q15 vector by a scalar.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.3 2010/11/29
    00015 *    Re-organized the CMSIS folders and updated documentation.
    00016 *
    00017 * Version 1.0.2 2010/11/11
    00018 *    Documentation updated.
    00019 *
    00020 * Version 1.0.1 2010/10/05
    00021 *    Production release and review comments incorporated.
    00022 *
    00023 * Version 1.0.0 2010/09/20
    00024 *    Production release and review comments incorporated
    00025 *
    00026 * Version 0.0.7  2010/06/10
    00027 *    Misra-C changes done
    00028 * -------------------------------------------------------------------- */
    00029
    00030 #include "arm_math.h"
    00031
    00057 void arm_scale_q15(
    00058   q15_t * pSrc,
    00059   q15_t scaleFract,
    00060   int8_t shift,
    00061   q15_t * pDst,
    00062   uint32_t blockSize)
    00063 {
    00064   int8_t kShift = 15 - shift;                    /* shift to apply after scaling */
    00065   uint32_t blkCnt;                               /* loop counter */
    00066   q15_t in1, in2;                                /* Temporary variables */
    00067
    00068
    00069   /*loop Unrolling */
    00070   blkCnt = blockSize >> 2u;
    00071
    00072   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00073    ** a second loop below computes the remaining 1 to 3 samples. */
    00074   while(blkCnt > 0u)
    00075   {
    00076     /* Reading 2 inputs from memory */
    00077     in1 = *pSrc++;
    00078     in2 = *pSrc++;
    00079     /* C = A * scale */
    00080     /* Scale the inputs and then store the 2 results in the destination buffer
    00081      * in single cycle by packing the outputs */
    00082     *__SIMD32(pDst)++ =
    00083       __PKHBT(__SSAT((in1 * scaleFract) >> kShift, 16),
    00084               __SSAT((in2 * scaleFract) >> kShift, 16), 16);
    00085
    00086     in1 = *pSrc++;
    00087     in2 = *pSrc++;
    00088
    00089     *__SIMD32(pDst)++ =
    00090       __PKHBT(__SSAT((in1 * scaleFract) >> kShift, 16),
    00091               __SSAT((in2 * scaleFract) >> kShift, 16), 16);
    00092
    00093     /* Decrement the loop counter */
    00094     blkCnt--;
    00095   }
    00096
    00097   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00098    ** No loop unrolling is used. */
    00099   blkCnt = blockSize % 0x4u;
    00100
    00101   while(blkCnt > 0u)
    00102   {
    00103     /* C = A * scale */
    00104     /* Scale the input and then store the result in the destination buffer. */
    00105     *pDst++ = (q15_t) (__SSAT(((*pSrc++) * scaleFract) >> kShift, 16));
    00106
    00107     /* Decrement the loop counter */
    00108     blkCnt--;
    00109   }
    00110 }
    00111

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