text: /* ----------------------------------------------------------------------    
  * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
  *    
  * $Date:        31. July 2014 
  * $Revision: 	V1.4.4  
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:	    arm_cfft_q31.c   
  *    
  * Description:	Combined Radix Decimation in Frequency CFFT Floating point processing function
  *    
  * 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"
  
  extern void arm_radix4_butterfly_q31(
      q31_t * pSrc,
      uint32_t fftLen,
      q31_t * pCoef,
      uint32_t twidCoefModifier);
  
  extern void arm_radix4_butterfly_inverse_q31(
      q31_t * pSrc,
      uint32_t fftLen,
      q31_t * pCoef,
      uint32_t twidCoefModifier);
  
  extern void arm_bitreversal_32(
      uint32_t * pSrc,
      const uint16_t bitRevLen,
      const uint16_t * pBitRevTable);
      
  void arm_cfft_radix4by2_q31(
      q31_t * pSrc,
      uint32_t fftLen,
      const q31_t * pCoef);
      
  void arm_cfft_radix4by2_inverse_q31(
      q31_t * pSrc,
      uint32_t fftLen,
      const q31_t * pCoef);
  
  /**   
  * @ingroup groupTransforms   
  */
  
  /**
  * @addtogroup ComplexFFT   
  * @{   
  */
  
  /**   
  * @details   
  * @brief       Processing function for the floating-point complex FFT.
  * @param[in]      *S    points to an instance of the floating-point CFFT structure.  
  * @param[in, out] *p1   points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.  
  * @param[in]     ifftFlag       flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.  
  * @param[in]     bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.  
  * @return none.  
  */
  
  void arm_cfft_q31( 
      const arm_cfft_instance_q31 * S, 
      q31_t * p1,
      uint8_t ifftFlag,
      uint8_t bitReverseFlag)
  {
      uint32_t L = S->fftLen;
  
      if(ifftFlag == 1u)
      {
          switch (L) 
          {
          case 16: 
          case 64:
          case 256:
          case 1024:
          case 4096:
              arm_radix4_butterfly_inverse_q31  ( p1, L, (q31_t*)S->pTwiddle, 1 );
              break;
              
          case 32:
          case 128:
          case 512:
          case 2048:
              arm_cfft_radix4by2_inverse_q31  ( p1, L, S->pTwiddle );
              break;
          }  
      }
      else
      {
          switch (L) 
          {
          case 16: 
          case 64:
          case 256:
          case 1024:
          case 4096:
              arm_radix4_butterfly_q31  ( p1, L, (q31_t*)S->pTwiddle, 1 );
              break;
              
          case 32:
          case 128:
          case 512:
          case 2048:
              arm_cfft_radix4by2_q31  ( p1, L, S->pTwiddle );
              break;
          }  
      }
      
      if( bitReverseFlag )
          arm_bitreversal_32((uint32_t*)p1,S->bitRevLength,S->pBitRevTable);    
  }
  
  /**    
  * @} end of ComplexFFT group    
  */
  
  void arm_cfft_radix4by2_q31(
      q31_t * pSrc,
      uint32_t fftLen,
      const q31_t * pCoef) 
  {    
      uint32_t i, l;
      uint32_t n2, ia;
      q31_t xt, yt, cosVal, sinVal;
      q31_t p0, p1;
      
      n2 = fftLen >> 1;    
      ia = 0;
      for (i = 0; i < n2; i++)
      {
          cosVal = pCoef[2*ia];
          sinVal = pCoef[2*ia + 1];
          ia++;
          
          l = i + n2;
          xt = (pSrc[2 * i] >> 2) - (pSrc[2 * l] >> 2);
          pSrc[2 * i] = (pSrc[2 * i] >> 2) + (pSrc[2 * l] >> 2);
          
          yt = (pSrc[2 * i + 1] >> 2) - (pSrc[2 * l + 1] >> 2);
          pSrc[2 * i + 1] = (pSrc[2 * l + 1] >> 2) + (pSrc[2 * i + 1] >> 2);
          
          mult_32x32_keep32_R(p0, xt, cosVal);
          mult_32x32_keep32_R(p1, yt, cosVal);
          multAcc_32x32_keep32_R(p0, yt, sinVal); 
          multSub_32x32_keep32_R(p1, xt, sinVal);
          
          pSrc[2u * l] = p0 << 1;
          pSrc[2u * l + 1u] = p1 << 1;
      
      }
  
      // first col
      arm_radix4_butterfly_q31( pSrc, n2, (q31_t*)pCoef, 2u);
      // second col
      arm_radix4_butterfly_q31( pSrc + fftLen, n2, (q31_t*)pCoef, 2u);
  			
      for (i = 0; i < fftLen >> 1; i++)
      {
          p0 = pSrc[4*i+0];
          p1 = pSrc[4*i+1];
          xt = pSrc[4*i+2];
          yt = pSrc[4*i+3];
          
          p0 <<= 1;
          p1 <<= 1;
          xt <<= 1;
          yt <<= 1;
          
          pSrc[4*i+0] = p0;
          pSrc[4*i+1] = p1;
          pSrc[4*i+2] = xt;
          pSrc[4*i+3] = yt;
      }
  
  }
  
  void arm_cfft_radix4by2_inverse_q31(
      q31_t * pSrc,
      uint32_t fftLen,
      const q31_t * pCoef) 
  {    
      uint32_t i, l;
      uint32_t n2, ia;
      q31_t xt, yt, cosVal, sinVal;
      q31_t p0, p1;
      
      n2 = fftLen >> 1;    
      ia = 0;
      for (i = 0; i < n2; i++)
      {
          cosVal = pCoef[2*ia];
          sinVal = pCoef[2*ia + 1];
          ia++;
          
          l = i + n2;
          xt = (pSrc[2 * i] >> 2) - (pSrc[2 * l] >> 2);
          pSrc[2 * i] = (pSrc[2 * i] >> 2) + (pSrc[2 * l] >> 2);
          
          yt = (pSrc[2 * i + 1] >> 2) - (pSrc[2 * l + 1] >> 2);
          pSrc[2 * i + 1] = (pSrc[2 * l + 1] >> 2) + (pSrc[2 * i + 1] >> 2);
          
          mult_32x32_keep32_R(p0, xt, cosVal);
          mult_32x32_keep32_R(p1, yt, cosVal);
          multSub_32x32_keep32_R(p0, yt, sinVal); 
          multAcc_32x32_keep32_R(p1, xt, sinVal);
          
          pSrc[2u * l] = p0 << 1;
          pSrc[2u * l + 1u] = p1 << 1;
      
      }
  
      // first col
      arm_radix4_butterfly_inverse_q31( pSrc, n2, (q31_t*)pCoef, 2u);
      // second col
      arm_radix4_butterfly_inverse_q31( pSrc + fftLen, n2, (q31_t*)pCoef, 2u);
  			
      for (i = 0; i < fftLen >> 1; i++)
      {
          p0 = pSrc[4*i+0];
          p1 = pSrc[4*i+1];
          xt = pSrc[4*i+2];
          yt = pSrc[4*i+3];
          
          p0 <<= 1;
          p1 <<= 1;
          xt <<= 1;
          yt <<= 1;
          
          pSrc[4*i+0] = p0;
          pSrc[4*i+1] = p1;
          pSrc[4*i+2] = xt;
          pSrc[4*i+3] = yt;
      }
  }
  
  