/// <summary>
/// 读取目标IP的信息
/// </summary>
/// <param name="fs"></param>
/// <param name="reader"></param>
/// <param name="offset"></param>
/// <param name="ipToLoc"></param>
/// <param name="ipBytes"></param>
/// <returns></returns>
private IPLocation GetIPInfo(FileStream fs, BinaryReader reader, long offset, IPAddress ipToLoc, byte[] ipBytes)
{
fs.Position = offset;
//确认目标IP在记录的IP范围内
var endIP = reader.ReadBytes(4);
var endIpVal = BitConverter.ToUInt32(endIP, 0);
var ipVal = BitConverter.ToUInt32(ipBytes, 0);
if (endIpVal < ipVal)
{
return(null);
}
string country;
string zone;
//读取重定向模式字节
var pattern = reader.ReadByte();
if (pattern == RedirectMode.Mode_1)
{
var countryOffsetBytes = reader.ReadBytes(IPFormat.RecOffsetLength);
var countryOffset = IPFormat.ToUint(countryOffsetBytes);
if (countryOffset == 0)
{
return(GetUnknownLocation(ipToLoc));
}
fs.Position = countryOffset;
if (fs.ReadByte() == RedirectMode.Mode_2)
{
return(ReadMode2Record(fs, reader, ipToLoc));
}
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));
}
/// <summary>
/// 按模式2读取记录
/// </summary>
/// <param name="fs"></param>
/// <param name="reader"></param>
/// <param name="ip"></param>
/// <returns></returns>
private IPLocation ReadMode2Record(FileStream fs, BinaryReader reader, IPAddress ip)
{
var countryOffset = IPFormat.ToUint(reader.ReadBytes(IPFormat.RecOffsetLength));
var curOffset = Convert.ToUInt32(fs.Position);
if (countryOffset == 0)
{
return(GetUnknownLocation(ip));
}
fs.Position = countryOffset;
var country = ReadString(reader);
var zone = ReadZone(fs, reader, curOffset);
return(new IPLocation(ip, country, zone));
}
/// <summary>
/// 读取区域信息
/// </summary>
/// <param name="fs"></param>
/// <param name="reader"></param>
/// <param name="offset"></param>
/// <returns></returns>
private string ReadZone(FileStream fs, BinaryReader reader, uint offset)
{
fs.Position = offset;
var b = reader.ReadByte();
if (b == RedirectMode.Mode_1 || b == RedirectMode.Mode_2)
{
var zoneOffset = IPFormat.ToUint(reader.ReadBytes(3));
if (zoneOffset == 0)
{
return(IPFormat.UnknownZone);
}
return(ReadZone(fs, reader, zoneOffset));
}
fs.Position--;
return(ReadString(reader));
}