private IPLocation GetIPInfo(FileStream fs, BinaryReader reader, long offset, IPAddress ipToLoc, Byte[] ipBytes)
{
fs.Position = offset;
//To confirm that the given ip is within the range of record IP range
byte[] endIP = reader.ReadBytes(4);
uint endIpVal = BitConverter.ToUInt32(endIP, 0);
uint ipVal = BitConverter.ToUInt32(ipBytes, 0);
if (endIpVal < ipVal)
{
return(null);
}
string country;
string zone;
//Read the Redirection pattern byte
Byte pattern = reader.ReadByte();
if (pattern == RedirectMode.Mode_1)
{
Byte[] countryOffsetBytes = reader.ReadBytes(IPFormat.RecOffsetLength);
uint countryOffset = IPFormat.ToUint(countryOffsetBytes);
if (countryOffset == 0)
{
return(GetUnknownLocation(ipToLoc));
}
fs.Position = countryOffset;
if (fs.ReadByte() == RedirectMode.Mode_2)
{
return(ReadMode2Record(fs, reader, ipToLoc));
}
else
{
fs.Position--;
country = ReadString(reader);
zone = ReadZone(fs, reader, Convert.ToUInt32(fs.Position));
}
}
else if (pattern == RedirectMode.Mode_2)
{
return(ReadMode2Record(fs, reader, ipToLoc));
}
else
{
fs.Position--;
country = ReadString(reader);
zone = ReadZone(fs, reader, Convert.ToUInt32(fs.Position));
}
return(new IPLocation(ipToLoc, country, zone));
}
//When it is in Mode 2
private IPLocation ReadMode2Record(FileStream fs, BinaryReader reader, IPAddress ip)
{
uint countryOffset = IPFormat.ToUint(reader.ReadBytes(IPFormat.RecOffsetLength));
uint curOffset = Convert.ToUInt32(fs.Position);
if (countryOffset == 0)
{
return(GetUnknownLocation(ip));
}
fs.Position = countryOffset;
string country = ReadString(reader);
string zone = ReadZone(fs, reader, curOffset);
return(new IPLocation(ip, country, zone));
}
//Retrieve the zone info
private string ReadZone(FileStream fs, BinaryReader reader, uint offset)
{
fs.Position = offset;
byte b = reader.ReadByte();
if (b == RedirectMode.Mode_1 || b == RedirectMode.Mode_2)
{
uint zoneOffset = IPFormat.ToUint(reader.ReadBytes(3));
if (zoneOffset == 0)
{
return(IPFormat.UnknownZone);
}
return(ReadZone(fs, reader, zoneOffset));
}
else
{
fs.Position--;
return(ReadString(reader));
}
}