/*
retorna o tipo de frame verificando o campo de controlo
*/
char * verifyFrameType(char * frame) {
switch(frame[2]) {
case C_SET:
return "set";
break;
case C_DISC:
return "disc";
break;
case C_UA:
return "ua";
break;
case RR(1):
return "rr1";
break;
case RR(0):
return "rr0";
break;
case REJ(0):
return "rej0";
break;
case REJ(1):
return "rej1";
break;
case C_I0:
return "I0";
break;
case C_I1:
return "I1";
break;
}
}
/*
Cria e envia uma trama do tipo type (Não funcional para tipo I)
*/
int buildFrame(int flag, char * type) {
info->frameSend[0] = F;
if (type == "set")
info->frameSend[2] = C_SET;
else if (type == "ua")
info->frameSend[2] = C_UA;
else if (type == "disc")
info->frameSend[2] = C_DISC;
else if (!strcmp(type, "rr1"))
info->frameSend[2] = RR(1);
else if (!strcmp(type,"rr0"))
info->frameSend[2] = RR(0);
else if (!strcmp(type,"rej0"))
info->frameSend[2] = REJ(0);
else if (!strcmp(type,"rej1"))
info->frameSend[2] = REJ(0);
else
return 0;
info->frameSend[1] = campo_endereco(info->flag, info->frameSend[2]);
info->frameSend[3] = info->frameSend[1]^info->frameSend[2];
info->frameSend[4] = F;
info->frameSendLength = 5;
//printf("Trama composta %s: 0x%x 0x%x 0x%x 0x%x 0x%x \n", type, info->frameSend[0], info->frameSend[1], info->frameSend[2], info->frameSend[3], info->frameSend[4]);
return 1;
}
int llwrite(int fd, unsigned char* buffer, int length){
//printf("entrei no llwrite\n");
char *bufferStuffed;
char header[] = { FLAG, 0x03, I(ll.sequenceNumber), header[1]^header[2] };
char dataBCC = generateBCC((char*)buffer, length);
char* toStuff = malloc(length+1);
memcpy(toStuff, buffer, length);
toStuff[length] = dataBCC;
int n= byteStuffing(toStuff, length+1, &bufferStuffed);
//int k;
//puts("");
//for (k=0;k<n;k++){
//printf("\n%d\n", bufferStuffed[k]);
//}
// puts("");
char* message = (char*) malloc(n+6);
memcpy(message, header, 4);
memcpy(message+4, bufferStuffed, n);
message[n+4] = FLAG;
int wrote = 0;
while(!wrote)
wrote = write(fd, message, n+5);
stats.dataFramesTransmitted++;
//puts("message sent\n");
free(message);
free(bufferStuffed);
alarm(ll.timeOut);
Command command = receiveCommand(fd);
//was asked for new frame
if (command.command == RR(!ll.sequenceNumber)){
ll.sequenceNumber = (!ll.sequenceNumber);
retries = 0;
//puts("fui confirmado");
alarm(0);
return length;
}
//frame was rejected, resend
if (command.command == REJ(ll.sequenceNumber) || (command.command == NONE && ll.numTransmissions > retries)){
if (command.command == NONE){
stats.timeouts++;
//printf("\nNumber of retries: %d\n", retries);
alarm(0);
}
//puts("byte was rejected,resending or no response\n");
stats.rejs++;
return llwrite(fd, buffer, length);
}
else{
//puts("eu esperei mas o reader nao me quis responder :(");
return -1;
}
return length;
}
int llread(int fd, unsigned char **buffer){
//printf("preparing to read frame\n");
Command command = receiveCommand(fd);
//puts("llread:received command");
int repeated;
if (command.command == I(ll.sequenceNumber))
repeated = 0;
else if (command.command == I(!ll.sequenceNumber))
repeated = 1;
else if (command.command == DISC){
//printf("llread: disconnecting\n");
while(!sendByte(fd, 0x01, DISC)){}
//puts("llread: disc confirmation sent\n");
command = receiveCommand(fd);
if (command.command != UA){
//puts("llread: didnt receive UA after disc confirmation\n");
return E_GENERIC;
}
else{
//puts("llread: connection successfully closed\n");
return E_CLOSED;
}
}
if (command.command == I(0) || command.command == I(1)){
//puts("llread: received a data frame\n");
//if we never saw this frame before, consider it
stats.dataFramesTransmitted++;
if(!repeated){
//puts("llread: new data frame\n");
int length = byteDeStuffing(&(command.data), command.size);
//puts("llread: destuffing succeeded\n");
int bccOK = verifyBCC(command.data, length, command.data[length-1]);
if(getRand() < RANDOM_REJ_CHANCE){
bccOK = 0;
// puts("\n randomly rejecting good packet");
}
//Reject frames with wrong BCC
if(!bccOK){
//puts("llread: frame was damaged, rejecting and rereading\n");
stats.rejs++;
while(!sendByte(fd, 0x03, REJ(ll.sequenceNumber) )){}
return llread(fd, buffer);
}
//accept the frame and confirm it
//puts("llread: frame bcc ok, accepting\n");
*buffer = (unsigned char*) malloc(length);
memcpy(*buffer, command.data, length);
while(!sendByte(fd,0x03, RR(!ll.sequenceNumber))){}
//puts("llread: receiver ready sent, message confirmed\n");
ll.sequenceNumber = !ll.sequenceNumber;
free(command.data);
//printf("%d length\n", length);
return length;
}
//this frame is repeated. Confirm it and ask for the new frame
else{
//puts("llread: message repeated");
while(!sendByte(fd, 0x03, RR(ll.sequenceNumber))){}
return E_GENERIC;
}
}
else{
//printf("received unexpected command 0x%02x\n",command.command);
return E_GENERIC;
}
return 0;
}
void state_machine(int state, char signal, char * type) {
if (state == START) {
if (signal == F) {
state = FLAG;
SET2[0]=signal;
}
}
else if (state == FLAG) {
if (signal == F)
state = FLAG;
else if ((signal == campo_endereco(!info->flag, C_SET) && type == "set")
|| (signal == campo_endereco(!info->flag, C_UA) && type == "ua")
|| (signal == campo_endereco(!info->flag, C_DISC) && type == "disc")
|| (signal == campo_endereco(!info->flag, RR(1)) && type == "rr1")
|| (signal == campo_endereco(!info->flag, RR(0)) && type == "rr0")
|| (signal == campo_endereco(!info->flag, REJ(1)) && type == "rej1")
|| (signal == campo_endereco(!info->flag, REJ(0)) && type == "rej0")
|| (signal == campo_endereco(!info->flag, C_I0) && type == "I0")
|| (signal == campo_endereco(!info->flag, C_I1) && type == "I1")) {
state = A_STATE;
SET2[1]=signal;
}
else
state = START;
}
else if (state == A_STATE) {
if (signal == F) {
state = FLAG;
}
else if ((signal == C_SET && type == "set")
|| (signal == C_UA && type == "ua")
|| (signal == C_DISC && type == "disc")
|| (signal == RR(1) && type == "rr1")
|| (signal == RR(0) && type == "rr0")
|| (signal == REJ(1) && type == "rej1")
|| (signal == REJ(0) && type == "rej0")
|| (signal == C_I0 && type == "I0")
|| (signal == C_I1 && type == "I1")) {
state = C;
SET2[2]=signal;
}
else
state = START;
}
else if (state == C) {
if (signal == F)
state = FLAG;
else if (signal == (SET2[1]^SET2[2])) {
state = BCC_STATE;
SET2[3]=signal;
}
else
state = START;
}
else if (state == BCC_STATE) {
if (signal == F) {
state = STOP2;
SET2[4]=signal;
}
else
state = START;
}
estado = state;
//printf("estado: %d \n", estado);
}
