/* ---------------------------------------------------------------------------- * Copyright (C) 2010-2013 ARM Limited. All rights reserved. * * $Date: 17. January 2013 * $Revision: V1.4.1 * * Project: CMSIS DSP Library * Title: arm_q31_to_q15.c * * Description: Converts the elements of the Q31 vector to Q15 vector. * * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * - Neither the name of ARM LIMITED nor the names of its contributors * may be used to endorse or promote products derived from this * software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ---------------------------------------------------------------------------- */ #include "arm_math.h" /** * @ingroup groupSupport */ /** * @addtogroup q31_to_x * @{ */ /** * @brief Converts the elements of the Q31 vector to Q15 vector. * @param[in] *pSrc points to the Q31 input vector * @param[out] *pDst points to the Q15 output vector * @param[in] blockSize length of the input vector * @return none. * * \par Description: * * The equation used for the conversion process is: * *
    
 * 	pDst[n] = (q15_t) pSrc[n] >> 16;   0 <= n < blockSize.    
 * 
* */ void arm_q31_to_q15( q31_t * pSrc, q15_t * pDst, uint32_t blockSize) { q31_t *pIn = pSrc; /* Src pointer */ uint32_t blkCnt; /* loop counter */ #ifndef ARM_MATH_CM0_FAMILY /* Run the below code for Cortex-M4 and Cortex-M3 */ q31_t in1, in2, in3, in4; q31_t out1, out2; /*loop Unrolling */ blkCnt = blockSize >> 2u; /* First part of the processing with loop unrolling. Compute 4 outputs at a time. ** a second loop below computes the remaining 1 to 3 samples. */ while(blkCnt > 0u) { /* C = (q15_t) A >> 16 */ /* convert from q31 to q15 and then store the results in the destination buffer */ in1 = *pIn++; in2 = *pIn++; in3 = *pIn++; in4 = *pIn++; /* pack two higher 16-bit values from two 32-bit values */ #ifndef ARM_MATH_BIG_ENDIAN out1 = __PKHTB(in2, in1, 16); out2 = __PKHTB(in4, in3, 16); #else out1 = __PKHTB(in1, in2, 16); out2 = __PKHTB(in3, in4, 16); #endif // #ifdef ARM_MATH_BIG_ENDIAN *__SIMD32(pDst)++ = out1; *__SIMD32(pDst)++ = out2; /* Decrement the loop counter */ blkCnt--; } /* If the blockSize is not a multiple of 4, compute any remaining output samples here. ** No loop unrolling is used. */ blkCnt = blockSize % 0x4u; #else /* Run the below code for Cortex-M0 */ /* Loop over blockSize number of values */ blkCnt = blockSize; #endif /* #ifndef ARM_MATH_CM0_FAMILY */ while(blkCnt > 0u) { /* C = (q15_t) A >> 16 */ /* convert from q31 to q15 and then store the results in the destination buffer */ *pDst++ = (q15_t) (*pIn++ >> 16); /* Decrement the loop counter */ blkCnt--; } } /** * @} end of q31_to_x group */