Go Back N C语言(有ACK)

#include <stdio.h>
#include <string.h>

#include "protocol.h"
#include "datalink.h"

#define DATA_TIMER  3000
#define ACK_TIMER 1500
#define MAX_SEQ 7

void inc(unsigned char* number)
{
	(*number)++;
	if(*number==MAX_SEQ+1)
	*number=0;
}

struct FRAME { 
    unsigned char kind; /* FRAME_DATA */
    unsigned char ack;
    unsigned char seq;
    unsigned char data[PKT_LEN]; 
    unsigned int  padding;
};

struct ACK_FRAME { 
    unsigned char kind; /* FRAME_DATA */
    unsigned char ack;
    unsigned int  padding;
};

static unsigned char frame_nr = 0;	//next frame to send
static unsigned char ack_expected = 0; 
static unsigned char buffer[MAX_SEQ+1][PKT_LEN];	//
static unsigned char nbuffered = 0;					//缓冲区大小	
static unsigned char frame_expected = 0;
static int phl_ready = 0;


static void put_frame(unsigned char *frame, int len)
{
    *(unsigned int *)(frame + len) = crc32(frame, len);
    send_frame(frame, len + 4);
    phl_ready = 0;
}

static void send_data_frame(void)
{
    struct FRAME s;

    s.kind = FRAME_DATA;
    s.seq = frame_nr;
	s.ack = (frame_expected+MAX_SEQ)%(MAX_SEQ+1);		// 另一端的ack
	memcpy(s.data, buffer[frame_nr], PKT_LEN);

    dbg_frame("Send DATA %d %d, ID %d\n", s.seq, s.ack, *(short *)s.data);

    put_frame((unsigned char *)&s, 3 + PKT_LEN);
    start_timer(frame_nr, DATA_TIMER);
	stop_ack_timer();
}

static void send_ack_frame(void)
{
    struct ACK_FRAME s;

    s.kind = FRAME_ACK;
    s.ack = (frame_expected+MAX_SEQ)%(MAX_SEQ+1);

    dbg_frame("Send ACK  %d\n", s.ack);

    put_frame((unsigned char *)&s, 2);
	stop_ack_timer();
}

int BetweenAN(unsigned char a , unsigned char b , unsigned char c)
{
	if(((a<=b)&&(b<c))||((c<a)&&(a<=b))||((b<c)&&(c<a)))
	{
		return 1;
	}
	else
	{
		return 0;
	}
}


int main(int argc, char **argv)
{
    int event, arg;
    struct FRAME f;
    int len = 0;
	unsigned char i;
    protocol_init(argc, argv); 
    lprintf("Designed by Jiang Yanjun, build: " __DATE__"  "__TIME__"\n");
	lprintf("The argc is: %d , the argv is: %s\n",argc,*argv);

    disable_network_layer();

    for (;;) {
        event = wait_for_event(&arg);

        switch (event) {
        case NETWORK_LAYER_READY:
			get_packet(buffer[frame_nr]); //取得数据
            nbuffered++;
            send_data_frame();
			inc(&frame_nr);	// next frame to send ++
            break;

        case PHYSICAL_LAYER_READY:
            phl_ready = 1;
            break;

        case FRAME_RECEIVED: 
            len = recv_frame((unsigned char *)&f, sizeof f);
            if (len < 5 || crc32((unsigned char *)&f, len) != 0) 
			{
                dbg_event("**** Receiver Error, Bad CRC Checksum\n");
                break;
            }
			else
			{
				if (f.kind == FRAME_ACK) 
					dbg_frame("Recv ACK  %d\n", f.ack);
				if (f.kind == FRAME_DATA) 
				{
					dbg_frame("Recv DATA %d %d, ID %d\n", f.seq, f.ack, *(short *)f.data);
					if (f.seq == frame_expected) 
					{
						dbg_frame("Recv DATA %d %d, ID %d\n put it to the NetWork\n", f.seq, f.ack, *(short *)f.data);
						put_packet(f.data, len - 7);
						inc(&frame_expected);  // frame expected ++
						start_ack_timer(ACK_TIMER);
					}
					else
						dbg_frame("Recv DATA %d %d, ID %d\n but it won't be put\n", f.seq, f.ack, *(short *)f.data);
				}

					while(BetweenAN(ack_expected,f.ack,frame_nr))
					{
						nbuffered--;
						stop_timer(ack_expected);
						inc(&ack_expected);
					}
				
//                send_ack_frame();
            } 

			
/*            if (f.ack == frame_nr)
			{
                stop_timer(frame_nr);
                nbuffered--;
                frame_nr = 1 - frame_nr;
            }*/
            break; 

        case DATA_TIMEOUT:
            dbg_event("---- DATA %d timeout\n", arg); 
			frame_nr=ack_expected;  //全部重发
			for(i=1;i<=nbuffered;i++)
			{
				send_data_frame();
				inc(&frame_nr);
			}

            break;

		case ACK_TIMEOUT:
			dbg_event("---- ACK %d timeout\n", arg); 
			send_ack_frame();
			break;
        }

		if (nbuffered < MAX_SEQ && phl_ready)
            enable_network_layer();
        else
            disable_network_layer();
   }
}

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