public static byte[] Decode(FileStream inStream, int length) // doc ra 1 mang byte[] co chieu dai la Length trong file Stego
{
int byteIndex = 0; // chay trong mang byte[]
int bitIndex = 0; // chay trong 8 bit cua tung byte
byte[] arrResult = new byte[length];
int byteRead; // byte doc vao tu file Stego
while ((byteRead = inStream.ReadByte()) != -1)
{
byte bit = BitWise.Extract((byte)byteRead, 0); // lay ra 1 bit vi tri thu 0;
// thay the bit nay vao trong Byte result[byteIndex] hien tai,o vi tri byteIndex
BitWise.Replace(ref arrResult[byteIndex], bitIndex++, bit);
if (bitIndex == 8) // ta da thu duoc 1 byte
{
bitIndex = 0;
byteIndex++;
}
if (byteIndex == length)
{
break; // ta da lay du noi dung thong diep
}
}
return(arrResult);
}
public static void Encode(FileStream inStream, byte[] message, FileStream outStream)
{
int byteRead; //1 byte doc vao tu inStream ( phai dung kieu int do ReadByte() tra ve kieu byte)
byte byteWrite; // 1 byte de viet vao ouStream
int i = 0; // chay trong mang byte Message
int j = 0; //chay tung bit trong 1 byte Message[i]
while ((byteRead = inStream.ReadByte()) != -1) // trong khi con chua ket thuc Stream
{
byteWrite = (byte)byteRead; // cast (ep kieu)
if (i < message.Length) // thong diep van con
{
byte bit = BitWise.Extract(message[i], j++); // trich 1 bit tu vi tri j tu message[i] ra
BitWise.Replace(ref byteWrite, 0, bit); // thay the bit vao vi tri 0 (LSB)
if (j == 8)
{
j = 0; i++;
} // da trich het 8 bit cua message[i]
}
//viet ra ouStream (co nhung truong hop nhung Byte cuoi khong bi thay doi
outStream.WriteByte(byteWrite);
}
if (i < message.Length) //i chua chay het mang Messsage[]
{
throw new Exception("Thong diep qua lon de giau");
}
}