text: /* ----------------------------------------------------------------------    
  * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
  *    
  * $Date: 16/06/16 3:44p $Revision: 	V.1.4.5
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:		arm_sub_q31.c    
  *    
  * Description:	Q31 vector subtraction.    
  *    
  * 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 groupMath    
   */
  
  /**    
   * @addtogroup BasicSub    
   * @{    
   */
  
  /**    
   * @brief Q31 vector subtraction.    
   * @param[in]       *pSrcA points to the first input vector    
   * @param[in]       *pSrcB points to the second input vector    
   * @param[out]      *pDst points to the output vector    
   * @param[in]       blockSize number of samples in each vector    
   * @return none.    
   *    
   * <b>Scaling and Overflow Behavior:</b>    
   * \par    
   * The function uses saturating arithmetic.    
   * Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] will be saturated.    
   */
  
  void arm_sub_q31(
    q31_t * pSrcA,
    q31_t * pSrcB,
    q31_t * pDst,
    uint32_t blockSize)
  {
    uint32_t blkCnt;                               /* loop counter */
  
  
  #ifndef ARM_MATH_CM0_FAMILY
  
  /* Run the below code for Cortex-M4 and Cortex-M3 */
    q31_t inA1, inA2, inA3, inA4;
    q31_t inB1, inB2, inB3, inB4;
  
    /*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 = A - B */
      /* Subtract and then store the results in the destination buffer. */
      inA1 = *pSrcA++;
      inA2 = *pSrcA++;
      inB1 = *pSrcB++;
      inB2 = *pSrcB++;
  
      inA3 = *pSrcA++;
      inA4 = *pSrcA++;
      inB3 = *pSrcB++;
      inB4 = *pSrcB++;
  
      *pDst++ = __QSUB(inA1, inB1);
      *pDst++ = __QSUB(inA2, inB2);
      *pDst++ = __QSUB(inA3, inB3);
      *pDst++ = __QSUB(inA4, inB4);
  
      /* 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;
  
    while(blkCnt > 0u)
    {
      /* C = A - B */
      /* Subtract and then store the result in the destination buffer. */
      *pDst++ = __QSUB(*pSrcA++, *pSrcB++);
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
  #else
  
    /* Run the below code for Cortex-M0 */
  
    /* Initialize blkCnt with number of samples */
    blkCnt = blockSize;
  
    while(blkCnt > 0u)
    {
      /* C = A - B */
      /* Subtract and then store the result in the destination buffer. */
      *pDst++ = (q31_t) clip_q63_to_q31((q63_t) * pSrcA++ - *pSrcB++);
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
  #endif /* #ifndef ARM_MATH_CM0_FAMILY */
  
  }
  
  /**    
   * @} end of BasicSub group    
   */
  