/*									tab:4
 *
 *
 * Copyright (C) 2004 by North Carolina State University.  
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without written agreement is
 * hereby granted, provided that the above copyright notice, the following
 * two paragraphs and the author appear in all copies of this software.
 * 
 * IN NO EVENT SHALL THE NORTH CAROLINA STATE UNIVERSITY BE LIABLE TO ANY PARTY 
 * FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING 
 * OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE NORTH
 * CAROLINA STATE UNIVERSITY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * THE NORTH CAROLINA STATE UNIVERSITY SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE NORTH CAROLINA STATE UNIVERSITY HAS NO OBLIGATION 
 * TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
 *
 * Authors: Rongfang Li
 * Date:    4/25/04
 */

includes PolyOne;

module ComputeKeyM16 {   /* used to evaluate key  */
  provides{
	 interface ComputeKey;
  }
}

implementation {  
 
  uint16_t f_poly16(uint16_t *b,uint16_t x){         
     
	uint16_t b2,s2=0;
	uint32_t s1=0;	
	uint32_t s;
	uint8_t i,j;
	uint16_t md0,mdv;

//	dbg(DBG_USR1,"c= %d\n",*b);
//	dbg(DBG_USR1,"x= %d\n",x);

	for(i=T+1;i>0;i--){             
       
		j=i-1;
	
		if(s2) s=(uint32_t )x<<16;
		else s=s1*x;

		md0=s&0xffff;
		mdv=s>>16;

		if(md0>=mdv) s=md0-mdv;
		else         s=65536u+1+md0-mdv;   

		if(b[j]!=0){  /* b[j] is between 1 and 65535 */
			s = s+b[j];
//			dbg(DBG_USR1,"poly+= %d\n",s);
		} else{  /* b[j] is 0 or 65536  */     
			b2=j>>4;  /* j div 16 is the right shift j by 4 bits */
			j=j&15;   /* j mod 16, is the least 4 bits of j  */         
			b2=b[T+1+b2]>>j;  /* get the 9th bit of b[j] */
			b2 = b2&1; 
	 
			if(b2){  /* b[j] is 65536  */
	  			s = s+65536u;
//				dbg(DBG_USR1,"poly+= %d\n",s);
			}
	 
	/* else b[i-1]=0, nothing need to do. */
		} 

		md0=s&0xffff;
		mdv=s>>16;
	
		if(md0>=mdv) s=md0-mdv;
		else s=65536u+1+md0-mdv;   

		s1=s&0xffff;
		s2=s>>16;                  
    	}                     
    	return (uint16_t)s1;                    
  }   
  command void ComputeKey.compute(uint8_t *array, uint16_t ID, uint8_t *key)
  {
  	PolyShare *ptr;
  	uint16_t *key16;
  	
  	key16=(uint16_t *)key;
  	ptr=(PolyShare *)array;
  	
	key16[0] = f_poly16(ptr->poly_ceft1, ID);
	key16[1] = f_poly16(ptr->poly_ceft2, ID);
	key16[2] = f_poly16(ptr->poly_ceft3, ID);
	key16[3] = f_poly16(ptr->poly_ceft4, ID);
//	dbg(DBG_USR1,"key=%d  %d  %d  %d\n",key16[0],key16[1],key16[2],key16[3]);
  }

}