Question

ip数据报首部检验和的c语言或者C++程序

麻烦给写一个，谢谢，急用

Answer 1

/* Check sum calulation. data in buff, size, InSum is initial sum */
WORD CheckSum(WORD DT_XDATA * buff,WORD size,DWORD InSum) REENTRANT_SIG
{
/* TO DO:in packet memory high part of short is in low memory. add all data in
form of 16 bits get a result of 32 bits, add high 16 bits to low 16 bits two
times. get a 16 bits result then complement it. */

DWORD cksum = InSum;

/* sum all word except the last odd byte(if size is a odd num) */
WORD DT_XDATA * EndBuf = buff + size/2;
while(buff < EndBuf)
{
/* net order is equeal as host order in mirochip, so no need to change */
cksum += *(buff++);
}

/**((WORD xdata *)CheckSumInParam) = size;
*((WORD xdata *)(CheckSumInParam+2)) = buff;
asmAddCheckSum();
cksum = CheckSumOutParm;
*/

/* if has last odd byte. use this byte as the high part of 16 bits, and add. */
if((size & 0x0001) != 0)
cksum += (*buff) & 0xff00;

cksum = (cksum >> 16) + (cksum & 0xffff);
cksum += (cksum >>16);
return (WORD)(~cksum);
}

Answer 2

计科（软件）。。。

Answer 3

hhh