arm_float_to_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_float_to_q31.c  
00009 *  
00010 * Description:  Processing function for the Conversion from float to Q31  
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  
00027 #include "arm_math.h" 
00028  
00029 /**  
00030  * @ingroup groupSupport  
00031  */ 
00032  
00033 /**  
00034  * @defgroup float_to_x  Convert 32-bit floating point value  
00035  */ 
00036  
00037 /**  
00038  * @addtogroup float_to_x  
00039  * @{  
00040  */ 
00041  
00042 /**  
00043  * @brief Converts the elements of the floating-point vector to Q31 vector.  
00044  * @param[in]       *pSrc points to the floating-point input vector  
00045  * @param[out]      *pDst points to the Q31 output vector 
00046  * @param[in]       blockSize length of the input vector  
00047  * @return none.  
00048  *  
00049  *\par Description:  
00050  * \par 
00051  * The equation used for the conversion process is:  
00052  * 
00053  * <pre>  
00054  *  pDst[n] = (q31_t)(pSrc[n] * 2147483648);   0 <= n < blockSize.  
00055  * </pre>  
00056  * <b>Scaling and Overflow Behavior:</b>  
00057  * \par  
00058  * The function uses saturating arithmetic.  
00059  * Results outside of the allowable Q31 range[0x80000000 0x7FFFFFFF] will be saturated.  
00060  * 
00061  * \note In order to apply rounding, the library should be rebuilt with the ROUNDING macro   
00062  * defined in the preprocessor section of project options.   
00063  */ 
00064  
00065  
00066 void arm_float_to_q31( 
00067   float32_t * pSrc, 
00068   q31_t * pDst, 
00069   uint32_t blockSize) 
00070 { 
00071   float32_t *pIn = pSrc;                         /* Src pointer */ 
00072   uint32_t blkCnt;                               /* loop counter */ 
00073  
00074 #ifdef ARM_MATH_ROUNDING 
00075  
00076   float32_t in; 
00077  
00078 #endif 
00079  
00080  
00081   /*loop Unrolling */ 
00082   blkCnt = blockSize >> 2u; 
00083  
00084   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00085    ** a second loop below computes the remaining 1 to 3 samples. */ 
00086   while(blkCnt > 0u) 
00087   { 
00088 #ifdef ARM_MATH_ROUNDING 
00089     /* C = A * 32768 */ 
00090     /* convert from float to Q31 and then store the results in the destination buffer */ 
00091     in = *pIn++; 
00092     in = (in * 2147483648.0f); 
00093     in += in > 0 ? 0.5 : -0.5; 
00094     *pDst++ = clip_q63_to_q31((q63_t) (in)); 
00095  
00096     in = *pIn++; 
00097     in = (in * 2147483648.0f); 
00098     in += in > 0 ? 0.5 : -0.5; 
00099     *pDst++ = clip_q63_to_q31((q63_t) (in)); 
00100  
00101     in = *pIn++; 
00102     in = (in * 2147483648.0f); 
00103     in += in > 0 ? 0.5 : -0.5; 
00104     *pDst++ = clip_q63_to_q31((q63_t) (in)); 
00105  
00106     in = *pIn++; 
00107     in = (in * 2147483648.0f); 
00108     in += in > 0 ? 0.5 : -0.5; 
00109     *pDst++ = clip_q63_to_q31((q63_t) (in)); 
00110  
00111 #else 
00112  
00113     /* C = A * 2147483648 */ 
00114     /* convert from float to Q31 and then store the results in the destination buffer */ 
00115     *pDst++ = clip_q63_to_q31((q63_t) (*pIn++ * 2147483648.0f)); 
00116     *pDst++ = clip_q63_to_q31((q63_t) (*pIn++ * 2147483648.0f)); 
00117     *pDst++ = clip_q63_to_q31((q63_t) (*pIn++ * 2147483648.0f)); 
00118     *pDst++ = clip_q63_to_q31((q63_t) (*pIn++ * 2147483648.0f)); 
00119  
00120 #endif 
00121  
00122     /* Decrement the loop counter */ 
00123     blkCnt--; 
00124   } 
00125  
00126   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00127    ** No loop unrolling is used. */ 
00128   blkCnt = blockSize % 0x4u; 
00129  
00130   while(blkCnt > 0u) 
00131   { 
00132 #ifdef ARM_MATH_ROUNDING 
00133  
00134     /* C = A * 2147483648 */ 
00135     /* convert from float to Q31 and then store the results in the destination buffer */ 
00136     in = *pIn++; 
00137     in = (in * 2147483648.0f); 
00138     in += in > 0 ? 0.5 : -0.5; 
00139     *pDst++ = clip_q63_to_q31((q63_t) (in)); 
00140  
00141 #else 
00142  
00143     /* C = A * 2147483648 */ 
00144     /* convert from float to Q31 and then store the results in the destination buffer */ 
00145     *pDst++ = clip_q63_to_q31((q63_t) (*pIn++ * 2147483648.0f)); 
00146  
00147 #endif 
00148  
00149     /* Decrement the loop counter */ 
00150     blkCnt--; 
00151   } 
00152 } 
00153  
00154 /**  
00155  * @} end of float_to_x group  
00156  */