www.pudn.com > fast.zip > cancel.h

struct canceller 
  { canceller(float d)	{ delta = d; reset(); } 
    void reset(); 
    void insert(complex);		/* put new Tx value into canceller	     */ 
    complex get();			/* get predicted echo value		     */ 
    void update(complex);		/* given eps, update coeffs		     */ 
    void print(char*);			/* print coeffs				     */ 
 
private: 
    const int size = 2048;			/* power of 2, large enough so (size + ebeg - TRDELAY) is +ve	*/ 
    const int ebeg = -60;			/* start of near-end echo response (samples)			*/ 
    const int eend =  30;			/* end of near-end echo response (samples)			*/ 
    const int ncs = (eend-ebeg) / (SYMBLEN/2);	/* num. of coeffs						*/ 
    complex coeffs[ncs];			/* vectors of coefficients					*/ 
    complex in[size];				/* circular buffer for input samples				*/ 
    int next;					/* ptr to next place to insert					*/ 
    float delta; 
  };