#ifndef __UM_SLIP_COMMON_H
  #define __UM_SLIP_COMMON_H

  #define BUF_SIZE 1500
   /* two bytes each for a (pathological) max packet of escaped chars +  *
    * terminating END char + initial END char                            */
  #define ENC_BUF_SIZE (2 * BUF_SIZE + 2)

  
  /* SLIP protocol characters. */
  #define SLIP_END             0300	/* indicates end of frame	*/
  #define SLIP_ESC             0333	/* indicates byte stuffing	*/
  #define SLIP_ESC_END         0334	/* ESC ESC_END means END 'data'	*/
  #define SLIP_ESC_ESC         0335	/* ESC ESC_ESC means ESC 'data'	*/

  static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
                               int *esc)

  {
  	int ret;
  
  	switch(c){
  	case SLIP_END:
  		*esc = 0;
  		ret=*pos;
  		*pos=0;
  		return(ret);
  	case SLIP_ESC:
  		*esc = 1;
  		return(0);
  	case SLIP_ESC_ESC:
  		if(*esc){
  			*esc = 0;
  			c = SLIP_ESC;
  		}
  		break;
  	case SLIP_ESC_END:
  		if(*esc){
  			*esc = 0;
  			c = SLIP_END;
  		}
  		break;
  	}
  	buf[(*pos)++] = c;
  	return(0);
  }
  
  static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
  {
  	unsigned char *ptr = d;
  	unsigned char c;
  
  	/*
  	 * Send an initial END character to flush out any
  	 * data that may have accumulated in the receiver
  	 * due to line noise.
  	 */
  
  	*ptr++ = SLIP_END;
  
  	/*
  	 * For each byte in the packet, send the appropriate
  	 * character sequence, according to the SLIP protocol.
  	 */
  
  	while (len-- > 0) {
  		switch(c = *s++) {
  		case SLIP_END:
  			*ptr++ = SLIP_ESC;
  			*ptr++ = SLIP_ESC_END;
  			break;
  		case SLIP_ESC:
  			*ptr++ = SLIP_ESC;
  			*ptr++ = SLIP_ESC_ESC;
  			break;
  		default:
  			*ptr++ = c;
  			break;
  		}
  	}
  	*ptr++ = SLIP_END;
  	return (ptr - d);
  }

  struct slip_proto {
  	unsigned char ibuf[ENC_BUF_SIZE];
  	unsigned char obuf[ENC_BUF_SIZE];
  	int more; /* more data: do not read fd until ibuf has been drained */
  	int pos;
  	int esc;
  };

  static inline void slip_proto_init(struct slip_proto * slip)
  {
  	memset(slip->ibuf, 0, sizeof(slip->ibuf));
  	memset(slip->obuf, 0, sizeof(slip->obuf));
  	slip->more = 0;
  	slip->pos = 0;
  	slip->esc = 0;

  }

  extern int slip_proto_read(int fd, void *buf, int len,
  			   struct slip_proto *slip);
  extern int slip_proto_write(int fd, void *buf, int len,
  			    struct slip_proto *slip);
  
  #endif