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# arm_q31_to_q15.c

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    00001 /* ----------------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        15. July 2011
    00005 * $Revision:    V1.0.10
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_q31_to_q15.c
    00009 *
    00010 * Description:  Converts the elements of the Q31 vector to Q15 vector.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
    00013 *
    00014 * Version 1.0.10 2011/7/15
    00015 *    Big Endian support added and Merged M0 and M3/M4 Source code.
    00016 *
    00017 * Version 1.0.3 2010/11/29
    00018 *    Re-organized the CMSIS folders and updated documentation.
    00019 *
    00020 * Version 1.0.2 2010/11/11
    00021 *    Documentation updated.
    00022 *
    00023 * Version 1.0.1 2010/10/05
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 1.0.0 2010/09/20
    00027 *    Production release and review comments incorporated.
    00028 * ---------------------------------------------------------------------------- */
    00029
    00030 #include "arm_math.h"
    00031
    00059 void arm_q31_to_q15(
    00060   q31_t * pSrc,
    00061   q15_t * pDst,
    00062   uint32_t blockSize)
    00063 {
    00064   q31_t *pIn = pSrc;                             /* Src pointer */
    00065   uint32_t blkCnt;                               /* loop counter */
    00066
    00067 #ifndef ARM_MATH_CM0
    00068
    00069   /* Run the below code for Cortex-M4 and Cortex-M3 */
    00070
    00071   /*loop Unrolling */
    00072   blkCnt = blockSize >> 2u;
    00073
    00074   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00075    ** a second loop below computes the remaining 1 to 3 samples. */
    00076   while(blkCnt > 0u)
    00077   {
    00078     /* C = (q15_t) A >> 16 */
    00079     /* convert from q31 to q15 and then store the results in the destination buffer */
    00080     *pDst++ = (q15_t) (*pIn++ >> 16);
    00081     *pDst++ = (q15_t) (*pIn++ >> 16);
    00082     *pDst++ = (q15_t) (*pIn++ >> 16);
    00083     *pDst++ = (q15_t) (*pIn++ >> 16);
    00084
    00085     /* Decrement the loop counter */
    00086     blkCnt--;
    00087   }
    00088
    00089   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00090    ** No loop unrolling is used. */
    00091   blkCnt = blockSize % 0x4u;
    00092
    00093 #else
    00094
    00095   /* Run the below code for Cortex-M0 */
    00096
    00097   /* Loop over blockSize number of values */
    00098   blkCnt = blockSize;
    00099
    00100 #endif /* #ifndef ARM_MATH_CM0 */
    00101
    00102   while(blkCnt > 0u)
    00103   {
    00104     /* C = (q15_t) A >> 16 */
    00105     /* convert from q31 to q15 and then store the results in the destination buffer */
    00106     *pDst++ = (q15_t) (*pIn++ >> 16);
    00107
    00108     /* Decrement the loop counter */
    00109     blkCnt--;
    00110   }
    00111
    00112 }
    00113

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