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  1. /* ----------------------------------------------------------------------------    
  2. * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
  3. *    
  4. * $Date:        19. March 2015
  5. * $Revision:    V.1.4.5  
  6. *    
  7. * Project:          CMSIS DSP Library    
  8. * Title:                arm_q31_to_q7.c    
  9. *    
  10. * Description:  Converts the elements of the Q31 vector to Q7 vector.    
  11. *    
  12. * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  13. *  
  14. * Redistribution and use in source and binary forms, with or without
  15. * modification, are permitted provided that the following conditions
  16. * are met:
  17. *   - Redistributions of source code must retain the above copyright
  18. *     notice, this list of conditions and the following disclaimer.
  19. *   - Redistributions in binary form must reproduce the above copyright
  20. *     notice, this list of conditions and the following disclaimer in
  21. *     the documentation and/or other materials provided with the
  22. *     distribution.
  23. *   - Neither the name of ARM LIMITED nor the names of its contributors
  24. *     may be used to endorse or promote products derived from this
  25. *     software without specific prior written permission.
  26. *
  27. * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28. * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  29. * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  30. * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  31. * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  32. * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  33. * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  34. * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  35. * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36. * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  37. * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  38. * POSSIBILITY OF SUCH DAMAGE.    
  39. * ---------------------------------------------------------------------------- */
  40.  
  41. #include "arm_math.h"
  42.  
  43. /**    
  44.  * @ingroup groupSupport    
  45.  */
  46.  
  47. /**    
  48.  * @addtogroup q31_to_x    
  49.  * @{    
  50.  */
  51.  
  52. /**    
  53.  * @brief Converts the elements of the Q31 vector to Q7 vector.    
  54.  * @param[in]       *pSrc points to the Q31 input vector    
  55.  * @param[out]      *pDst points to the Q7 output vector  
  56.  * @param[in]       blockSize length of the input vector    
  57.  * @return none.    
  58.  *    
  59.  * \par Description:    
  60.  *    
  61.  * The equation used for the conversion process is:    
  62.  *  
  63.  * <pre>    
  64.  *      pDst[n] = (q7_t) pSrc[n] >> 24;   0 <= n < blockSize.    
  65.  * </pre>    
  66.  *  
  67.  */
  68.  
  69.  
  70. void arm_q31_to_q7(
  71.   q31_t * pSrc,
  72.   q7_t * pDst,
  73.   uint32_t blockSize)
  74. {
  75.   q31_t *pIn = pSrc;                             /* Src pointer */
  76.   uint32_t blkCnt;                               /* loop counter */
  77.  
  78. #ifndef ARM_MATH_CM0_FAMILY
  79.  
  80.   /* Run the below code for Cortex-M4 and Cortex-M3 */
  81.   q31_t in1, in2, in3, in4;
  82.   q7_t out1, out2, out3, out4;
  83.  
  84.   /*loop Unrolling */
  85.   blkCnt = blockSize >> 2u;
  86.  
  87.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
  88.    ** a second loop below computes the remaining 1 to 3 samples. */
  89.   while(blkCnt > 0u)
  90.   {
  91.     /* C = (q7_t) A >> 24 */
  92.     /* convert from q31 to q7 and then store the results in the destination buffer */
  93.     in1 = *pIn++;
  94.     in2 = *pIn++;
  95.     in3 = *pIn++;
  96.     in4 = *pIn++;
  97.  
  98.     out1 = (q7_t) (in1 >> 24);
  99.     out2 = (q7_t) (in2 >> 24);
  100.     out3 = (q7_t) (in3 >> 24);
  101.     out4 = (q7_t) (in4 >> 24);
  102.  
  103.     *__SIMD32(pDst)++ = __PACKq7(out1, out2, out3, out4);
  104.  
  105.     /* Decrement the loop counter */
  106.     blkCnt--;
  107.   }
  108.  
  109.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
  110.    ** No loop unrolling is used. */
  111.   blkCnt = blockSize % 0x4u;
  112.  
  113. #else
  114.  
  115.   /* Run the below code for Cortex-M0 */
  116.  
  117.   /* Loop over blockSize number of values */
  118.   blkCnt = blockSize;
  119.  
  120. #endif /* #ifndef ARM_MATH_CM0_FAMILY */
  121.  
  122.   while(blkCnt > 0u)
  123.   {
  124.     /* C = (q7_t) A >> 24 */
  125.     /* convert from q31 to q7 and then store the results in the destination buffer */
  126.     *pDst++ = (q7_t) (*pIn++ >> 24);
  127.  
  128.     /* Decrement the loop counter */
  129.     blkCnt--;
  130.   }
  131.  
  132. }
  133.  
  134. /**    
  135.  * @} end of q31_to_x group    
  136.  */
  137.