text: /* ----------------------------------------------------------------------    
  * Copyright (C) 2010 ARM Limited. All rights reserved.    
  *    
  * $Date: 14/06/07 1:57a $Revision: 	V1.1.0  
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:	    arm_cfft_radix4_init_q31.c    
  *    
  * Description:	Radix-4 Decimation in Frequency Q31 FFT & IFFT initialization function    
  *    
  * 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.    
  *    
  * Version 0.0.5  2010/04/26     
  * 	 incorporated review comments and updated with latest CMSIS layer    
  *    
  * Version 0.0.3  2010/03/10     
  *    Initial version    
  * -------------------------------------------------------------------- */
  
  #include "arm_math.h"
  #include "arm_common_tables.h"
  
  /**    
   * @ingroup groupTransforms    
   */
  
  /**    
   * @addtogroup Radix4_CFFT_CIFFT    
   * @{    
   */
  
  /**    
  *    
  * @brief  Initialization function for the Q31 CFFT/CIFFT.   
  * @param[in,out] *S             points to an instance of the Q31 CFFT/CIFFT structure.   
  * @param[in]     fftLen         length of the FFT.   
  * @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        The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLen</code> is not a supported value.   
  *    
  * \par Description:   
  * \par    
  * The parameter <code>ifftFlag</code> controls whether a forward or inverse transform is computed.    
  * Set(=1) ifftFlag for calculation of CIFFT otherwise  CFFT is calculated   
  * \par    
  * The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order.    
  * Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.    
  * \par    
  * The parameter <code>fftLen</code>	Specifies length of CFFT/CIFFT process. Supported FFT Lengths are 16, 64, 256, 1024.    
  * \par    
  * This Function also initializes Twiddle factor table pointer and Bit reversal table pointer.    
  */
  
  arm_status arm_cfft_radix4_init_q31(
    arm_cfft_radix4_instance_q31 * S,
    uint16_t fftLen,
    uint8_t ifftFlag,
    uint8_t bitReverseFlag)
  {
    /*  Initialise the default arm status */
    arm_status status = ARM_MATH_SUCCESS;
    /*  Initialise the FFT length */
    S->fftLen = fftLen;
    /*  Initialise the Twiddle coefficient pointer */
    S->pTwiddle = (q31_t *) twiddleCoefQ31;
    /*  Initialise the Flag for selection of CFFT or CIFFT */
    S->ifftFlag = ifftFlag;
    /*  Initialise the Flag for calculation Bit reversal or not */
    S->bitReverseFlag = bitReverseFlag;
  
    /*  Initializations of Instance structure depending on the FFT length */
    switch (S->fftLen)
    {
      /*  Initializations of structure parameters for 4096 point FFT */
    case 4096u:
      /*  Initialise the twiddle coef modifier value */
      S->twidCoefModifier = 1u;
      /*  Initialise the bit reversal table modifier */
      S->bitRevFactor = 1u;
      /*  Initialise the bit reversal table pointer */
      S->pBitRevTable = (uint16_t *) armBitRevTable;
      break;
  
      /*  Initializations of structure parameters for 1024 point FFT */
    case 1024u:
      /*  Initialise the twiddle coef modifier value */
      S->twidCoefModifier = 4u;
      /*  Initialise the bit reversal table modifier */
      S->bitRevFactor = 4u;
      /*  Initialise the bit reversal table pointer */
      S->pBitRevTable = (uint16_t *) & armBitRevTable[3];
      break;
  
    case 256u:
      /*  Initializations of structure parameters for 256 point FFT */
      S->twidCoefModifier = 16u;
      S->bitRevFactor = 16u;
      S->pBitRevTable = (uint16_t *) & armBitRevTable[15];
      break;
  
    case 64u:
      /*  Initializations of structure parameters for 64 point FFT */
      S->twidCoefModifier = 64u;
      S->bitRevFactor = 64u;
      S->pBitRevTable = (uint16_t *) & armBitRevTable[63];
      break;
  
    case 16u:
      /*  Initializations of structure parameters for 16 point FFT */
      S->twidCoefModifier = 256u;
      S->bitRevFactor = 256u;
      S->pBitRevTable = (uint16_t *) & armBitRevTable[255];
      break;
  
    default:
      /*  Reporting argument error if fftSize is not valid value */
      status = ARM_MATH_ARGUMENT_ERROR;
      break;
    }
  
    return (status);
  }
  
  /**    
   * @} end of Radix4_CFFT_CIFFT group    
   */
  