#include <stdio.h>
#include <stdlib.h>
#include "tcp.h"
#include "demux.h"

// Demux.c 
// This files implements the software demultiplexer that gets packets
// to the user space immediately.

#define MAX_ENTRIES 128
TableEntry DemuxTable[MAX_ENTRIES];

#define NUMBER_OF_HINTS 2
int Hints[NUMBER_OF_HINTS];  // Most recently looked up table entries

// Q operations.  Put here, instead of header file, because tcp
// file uses same ops but without pointers to the Q structure
#define HEAD(Q) (Q->head)
#define TAIL(Q) (Q->tail)
#define NOT_EMPTY(Q) (Q->head!=Q->tail)
#define Q_FULL(Q) (Q->head==(Q->tail+1)%MAX_Q_SIZE)
#define ENQ(Q) (Q->tail=(Q->tail+1)%MAX_Q_SIZE)
#define DEQ(Q) (Q->head=(Q->head+1)%MAX_Q_SIZE)

// Initialize the demux table.  If Q is NULL, table entry is empty
void InitTable()
{
 	int i;
 	for (i=0; i<MAX_ENTRIES; i++) {
 		DemuxTable[i].SourceIP=0;
		DemuxTable[i].Ports=0;
		DemuxTable[i].ProtocolType=0;
		DemuxTable[i].UserQ=NULL;
		
 		}
}

// Puts a new socket into the table, returns if it was successful
BOOL CreateSocket(unsigned long int SourceIP,
	unsigned long int DestPort, 
	unsigned long int SourcePort,
	unsigned short int ProtocolType,
	Q *UserQ)   // Where incoming packets are put
{
	int TableLoc;
	// Find empty spot
	for (TableLoc=0; TableLoc<MAX_ENTRIES; TableLoc++) {
		if (DemuxTable[TableLoc].UserQ==NULL) {
 			DemuxTable[TableLoc].SourceIP=SourceIP;
			DemuxTable[TableLoc].Ports=SourcePort<<16 | DestPort;
			DemuxTable[TableLoc].ProtocolType=ProtocolType;
			DemuxTable[TableLoc].UserQ=UserQ;
			return TRUE;
               }
		}
	return FALSE;
}

// Removes an entry from the table, returns if it was successful
BOOL FreeSocket(unsigned long int SourceIP,
	unsigned long int DestPort, 
	unsigned long int SourcePort,
	unsigned short int ProtocolType)
{
	int TableLoc;
	
	DestPort=SourcePort<<16 | DestPort;
	// Find spot in table
	for (TableLoc=0; TableLoc<MAX_ENTRIES; TableLoc++) {
		if (DemuxTable[TableLoc].SourceIP==SourceIP &&
			     DemuxTable[TableLoc].Ports==DestPort &&
				DemuxTable[TableLoc].ProtocolType==ProtocolType) {
			DemuxTable[TableLoc].UserQ=NULL;
			return TRUE;
               }
		}
	return FALSE;
}

// This would put the packet on the OS queue, and let it deal with it
char *HandleUncommonPacket(TCPIP_Packet *InPacket)
{ return NULL; }  

// Actual demux routine
// NI's that use VCI's would be similar, but with simpler comparisons
// A well designed NI with VCI's would actually copy the data directly
//   to the receiver's buffer
void Demux(TCPIP_Packet *Packet)  // Assume it is a TCP packet...cast to 
{						    // UDP if necessary
	register int i;
	register Q *queue;
 	// Check to make sure that the packet is not a fragment
 	// If so, we have to send it off to the default OS handler
 	if ((Packet->flags_offset & 0x3FFF) != 0) {
 	     HandleUncommonPacket(Packet);
 		return;
 		}

 	// Check incoming packet for type (we already know it is IP)
 	if ((Packet->ttl_proto & 0x00ff) == TCP_PROTO_NUMBER) {
		// Check hint 0
 		i=Hints[0];
 		if (Packet->source_IP==DemuxTable[i].SourceIP &&
 	    	          Packet->ports==DemuxTable[i].Ports) {
 			queue=DemuxTable[i].UserQ;
 			// Push on user Q
 			if (Q_FULL(queue)) {
 				// HandleQOverflow(queue, Packet);
 				return;
 				}
 			queue->data[TAIL(queue)]=Packet;
 			ENQ(queue);
			return;
			} 			
		// Check hint 1
 		i=Hints[1];
 		if (Packet->source_IP==DemuxTable[i].SourceIP &&
 	    	          Packet->ports==DemuxTable[i].Ports) {
 			queue=DemuxTable[i].UserQ;
 			// Push on user Q
 			if (Q_FULL(queue)) {
 				// HandleQOverflow(queue, Packet);
 				return;
 				}
 			queue->data[TAIL(queue)]=Packet;
 			ENQ(queue);
			return;
			} 			
		// Do a full search 		
 		for (i=0; i<MAX_ENTRIES; i++) {
	 		if (Packet->source_IP==DemuxTable[i].SourceIP &&
 	    	          	Packet->ports==DemuxTable[i].Ports) {
 				queue=DemuxTable[i].UserQ;
 				// Push on user Q
	 			if (Q_FULL(queue)) {
 					// HandleQOverflow(queue, Packet);
 					return;
 					}
 				queue->data[TAIL(queue)]=Packet;
 				ENQ(queue);
				// Update hints
				Hints[1]=Hints[0];
				Hints[0]=i;
				return;
				} 			
			} 			
 			// Drop packet
 		}
	// Handle UDP or other packet type
}