module extension(input clk,output opp);
//DECLARATIONS
reg [15:0]array1[0:127];
reg [15:0]array2[0:49];
reg [15:0]indata;
reg [15:0]insign;
reg [15:0]insign1;
reg [31:0]index[0:49];
reg a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12,a13,a14,a15,a16;
reg b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16;
reg c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14,c15,c16;
reg d1,d2,d3,d4,d5,d6,d7,d8;
reg e1,e2,e3,e4,e5,e6,e7;
integer i=0,j,k=0,l,hh,c;
wire m,n,o,p,d,e;
// INITIALIZING ARRAY TO ZERO
initial
begin
for(l=0;l<50;l=l+1)
index[l]=32'b0;
end
//READING AN INCOMING DATA FILE FROM ARRAY1
initial
begin
$readmemb("indataex.txt",array1);
$display("incoming data");
end
//READING A SIGNATURE DATA FILE FROM ARRAY2
initial
begin
$readmemb("insignex.txt",array2);
$display("signature ");
end
// READING A SINGLE DATA FROM THE MEMORY FOR EVERY CLOCK PULSE DURING RISING EDGE
always @(posedge clk)
begin
if(i<128)
begin
indata=array1[i];
i=i+1;
end
else 
indata=0;
end
// ACTION TO BE PERFORMED DURING NEGATIVE EDGE OF THE CLOCK
always @(negedge clk)
begin
indata=0;
k=0;
end
//COMPARING MSB BITS OR PREFIX MATCHING
always @(posedge clk )
begin
for(j=0;j<50;j=j+1)
begin
insign=array2[j];
if (indata != 16'b0)
begin
if(indata[15:12] == insign[15:12])
begin
index[k]=j;
//$display("index [%0d]=%b",k,index[k]);
k=k+1;
end
//else
//$display("no intrusion");
end
end
end
//KNOWING WHICH INDEX HAS MATCHED
always @(k>0)
begin
if (indata != 16'b0)
begin
for(c=0;c<50;c=c+1)
begin
if(c<k)
begin
hh=index[c];
insign1=array2[hh];
//$display("the prefix matched: array value is array2[%0d] =%b",hh,insign1);
//SUFFIX MATCHING OR LSB BITS
if(indata[3:0]==insign1[3:0])
begin
//$display("the suffix matched: array value is array2[%0d] =%b",hh,insign1);
//COMPARING CENTRE BITS
if(indata[9:6]==insign1[9:6])
begin
//$display("the centre bits matched: array value is array2[%0d] =%b",hh,insign1);
//16 BIT INCOMING DATA 
a1 = insign1[0];
a2 = insign1[1];
a3 = insign1[2];
a4 = insign1[3];
a5 = insign1[4];
a6 = insign1[5];
a7 = insign1[6];
a8 = insign1[7];
a9 = insign1[8];
a10 = insign1[9];
a11 = insign1[10];
a12 = insign1[11];
a13 = insign1[12];
a14 = insign1[13];
a15 = insign1[14];
a16 = insign1[15];
//16 BIT MATCHED SIGNATURE (PREFIX ,SUFFIX AND CENTRE BITS)
b1 = indata[0];
b2 = indata[1];
b3 = indata[2];
b4 = indata[3];
b5 = indata[4];
b6 = indata[5];
b7 = indata[6];
b8 = indata[7];
b9 = indata[8];
b10 = indata[9];
b11 = indata[10];
b12 = indata[11];
b13 = indata[12];
b14 = indata[13];
b15 = indata[14];
b16 = indata[15];
//FILTER USING XNOR GATE
assign c1= (~a1 & ~b1)|(a1 & b1);
assign c2= (~a2 & ~b2)|(a2 & b2);
assign c3= (~a3 & ~b3)|(a3 & b3);
assign c4= (~a4 & ~b4)|(a4 & b4);
assign c5= (~a5 & ~b5)|(a5 & b5);
assign c6= (~a6 & ~b6)|(a6 & b6);
assign c7= (~a7 & ~b7)|(a7 & b7);
assign c8= (~a8 & ~b8)|(a8 & b8);
assign c9= (~a9 & ~b9)|(a9 & b9);
assign c10= (~a10 & ~b10)|(a10 & b10);
assign c11= (~a11 & ~b11)|(a11 & b11);
assign c12= (~a12 & ~b12)|(a12 & b12);
assign c13= (~a13 & ~b13)|(a13 & b13);
assign c14= (~a14 & ~b14)|(a14 & b14);
assign c15= (~a15 & ~b15)|(a15 & b15);
assign c16= (~a16 & ~b16)|(a16 & b16);
// COMBINING OUTPUT FROM XNOR GATE TO AND GATE 
assign d1 = c1 & c2;
assign d2 = c3 & c4;
assign d3 = c5 & c6;
assign d4 = c7 & c8;
assign d5 = c9 & c10;
assign d6 = c11 & c12;
assign d7 = c13 & c14;
assign d8 = c15 & c16;
assign e1 = d1 & d2;
assign e2 = d3 & d4;
assign e3 = d5 & d6;
assign e4 = d7 & d8;
assign e5 = e1 & e2;
assign e6 = e3 & e4;
assign e7 = e5 & e6;
//RESULT
if(e7==1)
$display("incoming data in the array[%0d]=%b is matched with signature, intrusion detected",hh,insign1);
else
$display("no intrusion");
end
//else
//$display("no intrusion");
end
//else
//$display("no intrusion");
end
end
end
end
endmodule