Category : Network Files
Archive   : KA9Q.ZIP
Filename : LCSUM.C

#include "global.h"
#if (defined(MPU8086) || defined(MPU8080) || defined(vax) || defined(iAPX286))
#define LITTLE_ENDIAN /* Low order bytes are first in memory */
#endif /* Almost all other machines are big-endian */
/*
* Word aligned linear buffer checksum routine. Called from mbuf checksum
* routine with simple args. Intent is that this routine may be replaced
* by assembly language routine for speed if so desired.
*/
int16
lcsum(wp,len)
register int16 *wp;
register int16 len;
{
int16 eac();
register int32 sum = 0;
int16 result;

while(len-- != 0)
sum += *wp++;
result = eac(sum);
#ifdef LITTLE_ENDIAN
/* Swap the result because of the (char *) to (int *) type punning */
result = (result << 8) | (result >> 8);
#endif
return result;
}