extern float xx[16384];
extern float ww[8192];



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 gen_w_r2(ww, 8192)£»
 bit_rev(xx, 4196)£»
 DSPF_sp_cfftr2_dit(xx,ww, 8192)£» 
 bit_rev(xx, 8192);


void gen_w_r2(float*w, int n)
{
	int i;
	float pi = 4.0 *atan(1.0);
	float e = pi *2.0 / n;

	for(i = 0; i < (n >> 1); i++)
	{
		w[2*i] = cos(i*e);
		w[2*i + 1] = sin(i*e);
	}	
}
void bit_rev(float*x, int n)
{
     int i, j, k;
     float rtemp, itemp;
     j = 0;
     for(i=1; i < (n-1); i++)
     {
        k = n >> 1;
        while(k <= j)
        {
             j -= k;
             k >>= 1;
        }
        j += k;
        if(i < j)
        {
           rtemp    = x[j*2];
           x[j*2]   = x[i*2];
           x[i*2]   = rtemp;
           itemp    = x[j*2+1];
           x[j*2+1] = x[i*2+1];
           x[i*2+1] = itemp;
        }
    }
}

void DSPF_sp_cfftr2_dit(float *x, float *w, short n)                     

 {                                                                   
         short n2, ie, ia, i, j, k, m;                                    
         float rtemp, itemp, c, s;                                        
                                                                          
         n2 = n;                                                          
         ie = 1;                                                          
                                                                          
         for(k=n; k > 1; k >>= 1)                                         
         {                                                                
            n2 >>= 1;                                                     
            ia = 0;                                                       
            for(j=0; j < ie; j++)                                         
            {                                                             
               c = w[2*j];                                                
               s = w[2*j+1];                                              
               for(i=0; i < n2; i++)                                      
               {                                                          
                  m = ia + n2;                                            
                  rtemp     = c*x[2*m]   + s*x[2*m+1];                
                  itemp     = c*x[2*m+1] - s*x[2*m];                  
                  x[2*m]    = x[2*ia]   - rtemp;                          
                  x[2*m+1]  = x[2*ia+1] - itemp;                          
                  x[2*ia]   = x[2*ia]   + rtemp;                          
                  x[2*ia+1] = x[2*ia+1] + itemp;                          
                  ia++;                                                   
               }                                                          
               ia += n2;                                                  
            }                                                             
            ie <<= 1;                                                     
         }                                                               
 }