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/* ----------------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 15. February 2012
* $Revision: V1.1.0
*
* 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
*
* Version 1.1.0 2012/02/15
* Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
* Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
* Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
* Documentation updated.
*
* Version 1.0.1 2010/10/05
* Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
* Production release and review comments incorporated.
* ---------------------------------------------------------------------------- */
#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:
*
* <pre>
* pDst[n] = (q15_t) pSrc[n] >> 16; 0 <= n < blockSize.
* </pre>
*
*/
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
/* 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 */
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
*/
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