arm_negate_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_negate_q31.c  
00009 *  
00010 * Description:  Negates Q31 vectors.  
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 negate  
00038  * @{  
00039  */ 
00040  
00041 /**  
00042  * @brief  Negates the elements of a Q31 vector.  
00043  * @param  *pSrc points to the input vector  
00044  * @param  *pDst points to the output vector  
00045  * @param  blockSize number of samples in the vector  
00046  * @return none.  
00047  *  
00048  * <b>Scaling and Overflow Behavior:</b>  
00049  * \par  
00050  * The function uses saturating arithmetic.  
00051  * The Q31 value -1 (0x80000000) will be saturated to the maximum allowable positive value 0x7FFFFFFF.  
00052  */ 
00053  
00054 void arm_negate_q31( 
00055   q31_t * pSrc, 
00056   q31_t * pDst, 
00057   uint32_t blockSize) 
00058 { 
00059   q31_t in;                                      /* Temporary variable */ 
00060   uint32_t blkCnt;                               /* loop counter */ 
00061  
00062  
00063   /*loop Unrolling */ 
00064   blkCnt = blockSize >> 2u; 
00065  
00066   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00067    ** a second loop below computes the remaining 1 to 3 samples. */ 
00068   while(blkCnt > 0u) 
00069   { 
00070     /* C = ~A */ 
00071     /* Negate and then store the results in the destination buffer. */ 
00072     in = *pSrc++; 
00073     *pDst++ = (in == 0x80000000) ? 0x7fffffff : -in; 
00074     in = *pSrc++; 
00075     *pDst++ = (in == 0x80000000) ? 0x7fffffff : -in; 
00076     in = *pSrc++; 
00077     *pDst++ = (in == 0x80000000) ? 0x7fffffff : -in; 
00078     in = *pSrc++; 
00079     *pDst++ = (in == 0x80000000) ? 0x7fffffff : -in; 
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 */ 
00092     /* Negate and then store the result in the destination buffer. */ 
00093     in = *pSrc++; 
00094     *pDst++ = (in == 0x80000000) ? 0x7fffffff : -in; 
00095  
00096     /* Decrement the loop counter */ 
00097     blkCnt--; 
00098   } 
00099 } 
00100  
00101 /**  
00102  * @} end of negate group  
00103  */