arm_scale_q31.c

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_q31.c  
00009 *  
00010 * Description:  Multiplies a Q31 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  
00032 /**  
00033  * @ingroup groupMath  
00034  */ 
00035  
00036 /**  
00037  * @addtogroup scale  
00038  * @{  
00039  */ 
00040  
00041 /**  
00042  * @brief Multiplies a Q31 vector by a scalar.  
00043  * @param[in]       *pSrc points to the input vector  
00044  * @param[in]       scaleFract fractional portion of the scale value  
00045  * @param[in]       shift number of bits to shift the result by  
00046  * @param[out]      *pDst points to the output vector  
00047  * @param[in]       blockSize number of samples in the vector  
00048  * @return none.  
00049  *  
00050  * <b>Scaling and Overflow Behavior:</b>  
00051  * \par  
00052  * The input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.31 format.  
00053  * These are multiplied to yield a 2.62 intermediate result and this is shifted with saturation to 1.31 format.  
00054  */ 
00055  
00056 void arm_scale_q31( 
00057   q31_t * pSrc, 
00058   q31_t scaleFract, 
00059   int8_t shift, 
00060   q31_t * pDst, 
00061   uint32_t blockSize) 
00062 { 
00063   int8_t kShift = 31 - shift;                    /* Shift to apply after scaling */ 
00064   uint32_t blkCnt;                               /* loop counter */ 
00065  
00066  
00067   /*loop Unrolling */ 
00068   blkCnt = blockSize >> 2u; 
00069  
00070   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00071    ** a second loop below computes the remaining 1 to 3 samples. */ 
00072   while(blkCnt > 0u) 
00073   { 
00074     /* C = A * scale */ 
00075     /* Scale the input and then store the results in the destination buffer. */ 
00076     *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
00077     *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
00078     *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
00079     *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
00080  
00081     /* Decrement the loop counter */ 
00082     blkCnt--; 
00083   } 
00084  
00085   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00086    ** No loop unrolling is used. */ 
00087   blkCnt = blockSize % 0x4u; 
00088  
00089   while(blkCnt > 0u) 
00090   { 
00091     /* C = A * scale */ 
00092     /* Scale the input and then store the result in the destination buffer. */ 
00093     *pDst++ = clip_q63_to_q31(((q63_t) * pSrc++ * scaleFract) >> kShift); 
00094  
00095     /* Decrement the loop counter */ 
00096     blkCnt--; 
00097   } 
00098 } 
00099  
00100 /**  
00101  * @} end of scale group  
00102  */