//
// $Id: Headers.cc,v 1.1.1.1 2000/03/10 16:32:19 engin Exp $
//
// Author(s): Ramesh Govindan

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <netinet/in.h>
#include "util/Types.hh"
#include "util/Trail.hh"
#include "network/Headers.hh"

U16
ICMP::cksum(int size)
{
    unsigned short* addr = (unsigned short*) this;
    int len = size;
    int nleft = len;
    u_short *w = addr;
    u_short answer;
    u_short odd_byte = 0;
    register int sum = 0;

    ASSERT((size % 2) == 0);	// For now, we assume even length

    /*
     *  Our algorithm is simple, using a 32 bit accumulator (sum),
     *  we add sequential 16 bit words to it, and at the end, fold
     *  back all the carry bits from the top 16 bits into the lower
     *  16 bits.
     */
    while( nleft > 1 )  {
        sum += *w++;
        nleft -= 2;
    }

    /* mop up an odd byte, if necessary */
    if( nleft == 1 ) {
        *(u_char *)(&odd_byte) = *(u_char *)w;
        sum += odd_byte;
    }

    /*
     * add back carry outs from top 16 bits to low 16 bits
     */
    sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
    sum += (sum >> 16);                     /* add carry */
    answer = ~sum;                          /* truncate to 16 bits */
    return (answer);
}

U16
IP::cksum()
{
    unsigned short* addr = (unsigned short*) this;
    int len = sizeof(IP);
    int nleft = len;
    u_short *w = addr;
    u_short answer;
    u_short odd_byte = 0;
    register int sum = 0;

    /*
     *  Our algorithm is simple, using a 32 bit accumulator (sum),
     *  we add sequential 16 bit words to it, and at the end, fold
     *  back all the carry bits from the top 16 bits into the lower
     *  16 bits.
     */
    while( nleft > 1 )  {
        sum += *w++;
        nleft -= 2;
    }

    /* mop up an odd byte, if necessary */
    if( nleft == 1 ) {
        *(u_char *)(&odd_byte) = *(u_char *)w;
        sum += odd_byte;
    }

    /*
     * add back carry outs from top 16 bits to low 16 bits
     */
    sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
    sum += (sum >> 16);                     /* add carry */
    answer = ~sum;                          /* truncate to 16 bits */
    return (answer);
}

U16
IGMP::cksum(int size)
{
    unsigned short* addr = (unsigned short*) this;
    int len = size;
    int nleft = len;
    u_short *w = addr;
    u_short answer;
    u_short odd_byte = 0;
    register int sum = 0;

    ASSERT((size % 2) == 0);	// For now, we assume even length

    /*
     *  Our algorithm is simple, using a 32 bit accumulator (sum),
     *  we add sequential 16 bit words to it, and at the end, fold
     *  back all the carry bits from the top 16 bits into the lower
     *  16 bits.
     */
    while( nleft > 1 )  {
        sum += *w++;
        nleft -= 2;
    }

    /* mop up an odd byte, if necessary */
    if( nleft == 1 ) {
        *(u_char *)(&odd_byte) = *(u_char *)w;
        sum += odd_byte;
    }

    /*
     * add back carry outs from top 16 bits to low 16 bits
     */
    sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
    sum += (sum >> 16);                     /* add carry */
    answer = ~sum;                          /* truncate to 16 bits */
    return (answer);
}

//  Copyright (c) 1994 by the University of Southern California.
//  All rights reserved.
//
//  Permission to use, copy, modify, and distribute this software and
//  its documentation in source and binary forms for lawful
//  non-commercial purposes and without fee is hereby granted, provided
//  that the above copyright notice appear in all copies and that both
//  the copyright notice and this permission notice appear in supporting
//  documentation, and that any documentation, advertising materials,
//  and other materials related to such distribution and use acknowledge
//  that the software was developed by the University of Southern
//  California and/or Information Sciences Institute.
//  The name of the University of Southern California may not
//  be used to endorse or promote products derived from this software
//  without specific prior written permission.
//
//  THE UNIVERSITY OF SOUTHERN CALIFORNIA DOES NOT MAKE ANY REPRESENTATIONS
//  ABOUT THE SUITABILITY OF THIS SOFTWARE FOR ANY PURPOSE.  THIS SOFTWARE IS
//  PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,
//  INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
//  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND 
//  NON-INFRINGEMENT.
//
//  IN NO EVENT SHALL USC, OR ANY OTHER CONTRIBUTOR BE LIABLE FOR ANY
//  SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES, WHETHER IN CONTRACT,
//  TORT, OR OTHER FORM OF ACTION, ARISING OUT OF OR IN CONNECTION WITH,
//  THE USE OR PERFORMANCE OF THIS SOFTWARE.
//
//  Questions concerning this software should be directed to 
//  scan@isi.edu.
//


