protected CZ_INDEX_INFO IndexInfoAtPos(UInt32 Index_Pos)
{
CZ_INDEX_INFO Index_Info = new CZ_INDEX_INFO();
//根据索引编号计算出在文件中在偏移位置
MemStream.Seek(Index_Set + 7 * Index_Pos, SeekOrigin.Begin);
Index_Info.IpSet = GetUInt32();
Index_Info.Offset = GetOffset();
MemStream.Seek(Index_Info.Offset, SeekOrigin.Begin);
Index_Info.IpEnd = GetUInt32();
return(Index_Info);
}
public string GetLocation(string IPValue)
{
if (!IsIpDatabaseInitialized)
{
throw new Exception("IP库尚未初始化！");
}
try
{
Initialize();
UInt32 ip = IPToUInt32(IPValue);
while (true)
{
//首先初始化本轮查找的区间
//区间头
Search_Set = IndexInfoAtPos(Search_Index_Set);
//区间尾
Search_End = IndexInfoAtPos(Search_Index_End);
//判断IP是否在区间头内
if (ip >= Search_Set.IpSet && ip <= Search_Set.IpEnd)
{
return(ReadAddressInfoAtOffset(Search_Set.Offset));
}
//判断IP是否在区间尾内
if (ip >= Search_End.IpSet && ip <= Search_End.IpEnd)
{
return(ReadAddressInfoAtOffset(Search_End.Offset));
}
//计算出区间中点
Search_Mid = IndexInfoAtPos((Search_Index_End + Search_Index_Set) / 2);
//判断IP是否在中点
if (ip >= Search_Mid.IpSet && ip <= Search_Mid.IpEnd)
{
return(ReadAddressInfoAtOffset(Search_Mid.Offset));
}
//本轮没有找到，准备下一轮
if (ip < Search_Mid.IpSet)
{
//IP比区间中点要小，将区间尾设为现在的中点，将区间缩小1倍。
Search_Index_End = (Search_Index_End + Search_Index_Set) / 2;
}
else
{
//IP比区间中点要大，将区间头设为现在的中点，将区间缩小1倍。
Search_Index_Set = (Search_Index_End + Search_Index_Set) / 2;
}
}
}
catch (Exception e)
{
Common.LogIt(e.ToString());
throw;
}
}
