// 通过重叠网络(在本实验中，是一个TCP连接)接收STCP段. 我们建议你使用recv()一次接收一个字节.
// 你需要查找"!&", 然后是seg_t, 最后是"!#". 这实际上需要你实现一个搜索的FSM, 可以考虑使用如下所示的FSM.
// SEGSTART1 -- 起点
// SEGSTART2 -- 接收到'!', 期待'&'
// SEGRECV -- 接收到'&', 开始接收数据
// SEGSTOP1 -- 接收到'!', 期待'#'以结束数据的接收
// 这里的假设是"!&"和"!#"不会出现在段的数据部分(虽然相当受限, 但实现会简单很多).
// 你应该以字符的方式一次读取一个字节, 将数据部分拷贝到缓冲区中返回给调用者.
//
// 注意: 还有一种处理方式可以允许"!&"和"!#"出现在段首部或段的数据部分. 具体处理方式是首先确保读取到!&，然后
// 直接读取定长的STCP段首部, 不考虑其中的特殊字符, 然后按照首部中的长度读取段数据, 最后确保以!#结尾.
//
// 注意: 在你剖析了一个STCP段之后, 你需要调用seglost()来模拟网络中数据包的丢失.
// 在sip_recvseg()的下面是seglost()的代码.
//
// 如果段丢失了, 就返回1, 否则返回0.
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
int sip_recvseg(int connection, seg_t* segPtr)
{
int state = 0,len=-1;
char c;
while(state == 0 || state == 1){
len = recv(connection,&c,sizeof(c),0);
if (len <= 0){
printf("sip recv !& failed!%d\n",len);
return 2;
}
if (state == 1)
if (c == '&') state = 2;
else if (c == '!') state = 1; else state = 0;
else;
if (state == 0)
if (c == '!') state = 1; else printf("%c",c);
}
//printf("sip recv !& success!\n");
len = recv(connection,(char*)segPtr,sizeof(stcp_hdr_t),0);
if (len < sizeof(stcp_hdr_t)){
printf("recv stcp_hdr_t failed!\n");
return 2;
}
state = 3;
//printf("sip recv header success!\n");
int datalen = segPtr->header.length;
len = recv(connection,(char*)(segPtr->data),datalen,0);
if (len < datalen){
printf("recv stcp_data failed!\n");
return 2;
}
state = 4;
//printf("sip recv data success!\n");
while(state == 4 || state == 5){
len = recv(connection,&c,sizeof(c),0);
if (len <= 0){
printf("sip recv !# failed!\n");
return 2;
}
if (state == 5)
if (c == '#') state = 6;
else if (c == '!') state = 5; else state = 4;
else;
if (state == 4)
if (c == '!') state = 5;
}
//printf("sip recv !# success!\n");
if (state == 6 && seglost() == 0) return 0; else{
printf("sip recv seglost.\n");
return 1;
}
}
//recv function
int recvf(sendseg_arg_t *ptr, int connection)
{
char buf[sizeof(sendseg_arg_t) + 2];
char c;
int idx = 0;
// state can be 0,1,2,3;
// 0 starting point
// 1 '!' received
// 2 '&' received, start receiving segment
// 3 '!' received,
// 4 '#' received, finish receiving segment
int state = 0;
while(recv(connection,&c,1,0)>0) {
if (state == 0) {
if(c=='!')
state = 1;
}
else if(state == 1) {
if(c=='&')
state = 2;
else
state = 0;
}
else if(state == 2) {
if(c=='!') {
buf[idx]=c;
idx++;
state = 3;
}
else {
buf[idx]=c;
idx++;
}
}
else if(state == 3) {
if(c=='#') {
buf[idx]=c;
memcpy(ptr, buf, idx - 1);
state = 0;
idx = 0;
//add segment error
if(seglost(&ptr->seg)>0) {
continue;
}
if(checkchecksum(&ptr->seg)<0) {
printf("checksum error,drop!\n");
continue;
}
return 1;
}
else if(c=='!') {
buf[idx]=c;
idx++;
}
else {
buf[idx]=c;
idx++;
state = 2;
}
}
}
return -1;
}
//SRT process uses this function to receive a sendseg_arg_t structure which contains a segment and its src node ID from the SNP process.
//Parameter network_conn is the TCP descriptor of the connection between the SRT process and the SNP process.
//When a segment is received, use seglost to determine if the segment should be discarded, also check the checksum.
//Return 1 if a sendseg_arg_t is succefully received, otherwise return -1.
int snp_recvseg(int network_conn, int* src_nodeID, seg_t* segPtr)
{
char buf[sizeof(sendseg_arg_t)+2];
char c;
int idx = 0;
// state can be 0,1,2,3;
// 0 starting point
// 1 '!' received
// 2 '&' received, start receiving segment
// 3 '!' received,
// 4 '#' received, finish receiving segment
int state = 0;
sendseg_arg_t *sendSegArg = (sendseg_arg_t *)malloc(sizeof(sendseg_arg_t));
// puts("in getsegToSend");
while(recv(network_conn,&c,1,0)>0) {
if (state == 0) {
if(c=='!')
state = 1;
}
else if(state == 1) {
if(c=='&')
state = 2;
else
state = 0;
}
else if(state == 2) {
if(c=='!') {
buf[idx]=c;
idx++;
state = 3;
}
else {
buf[idx]=c;
idx++;
}
}
else if(state == 3) {
if(c=='#') {
buf[idx]=c;
idx++;
memcpy(sendSegArg, buf, idx - 2);
*src_nodeID = sendSegArg->nodeID;
// printf("in getpktToSend, nextNodeID is %d\n", *nextNode);
*segPtr = sendSegArg->seg;
state = 0;
idx = 0;
if(seglost(segPtr)>0) {
printf("seg lost!\n");
continue;
}
if(checkchecksum(segPtr)<0) {
printf("checksum error, drop!\n");
continue;
}
free(sendSegArg);
return 1;
}
else if(c=='!') {
buf[idx]=c;
idx++;
}
else {
buf[idx]=c;
idx++;
state = 2;
}
}
}
free(sendSegArg);
return -1;
}
