/**
* initialize the db file
*
* @param raf
* @
*/
private void initDbFile(RandomAccessFile raf)
{
//1. zero fill the header part
raf.seek(0L);
raf.write(new byte[8]); //super block
raf.write(new byte[dbConfig.getTotalHeaderSize()]); //header block
headerPool = new LinkedList <HeaderBlock>();
indexPool = new LinkedList <IndexBlock>();
}
/**
* get the region with a int ip address with b-tree algorithm
*
* @param ip
* @
*/
public DataBlock btreeSearch(long ip)
{
//check and load the header
if (HeaderSip == null)
{
raf.seek(8L); //pass the super block
byte[] b = new byte[dbConfig.getTotalHeaderSize()];
// byte[] b = new byte[4096];
raf.readFully(b, 0, b.Length);
//fill the header
int len = b.Length >> 3, idx = 0; //b.lenght / 8
HeaderSip = new long[len];
HeaderPtr = new int[len];
long startIp, dataPtr2;
for (int i = 0; i < b.Length; i += 8)
{
startIp = Util.getIntLong(b, i);
dataPtr2 = Util.getIntLong(b, i + 4);
if (dataPtr2 == 0)
{
break;
}
HeaderSip[idx] = startIp;
HeaderPtr[idx] = (int)dataPtr2;
idx++;
}
headerLength = idx;
}
//1. define the index block with the binary search
if (ip == HeaderSip[0])
{
return(getByIndexPtr(HeaderPtr[0]));
}
else if (ip == HeaderSip[headerLength - 1])
{
return(getByIndexPtr(HeaderPtr[headerLength - 1]));
}
int l = 0, h = headerLength, sptr = 0, eptr = 0;
while (l <= h)
{
int m = (l + h) >> 1;
//perfetc matched, just return it
if (ip == HeaderSip[m])
{
if (m > 0)
{
sptr = HeaderPtr[m - 1];
eptr = HeaderPtr[m];
}
else
{
sptr = HeaderPtr[m];
eptr = HeaderPtr[m + 1];
}
break;
}
//less then the middle value
if (ip < HeaderSip[m])
{
if (m == 0)
{
sptr = HeaderPtr[m];
eptr = HeaderPtr[m + 1];
break;
}
else if (ip > HeaderSip[m - 1])
{
sptr = HeaderPtr[m - 1];
eptr = HeaderPtr[m];
break;
}
h = m - 1;
}
else
{
if (m == headerLength - 1)
{
sptr = HeaderPtr[m - 1];
eptr = HeaderPtr[m];
break;
}
else if (ip <= HeaderSip[m + 1])
{
sptr = HeaderPtr[m];
eptr = HeaderPtr[m + 1];
break;
}
l = m + 1;
}
}
//match nothing just stop it
if (sptr == 0)
{
return(null);
}
//2. search the index blocks to define the data
int blockLen = eptr - sptr, blen = IndexBlock.getIndexBlockLength();
byte[] iBuffer = new byte[blockLen + blen]; //include the right border block
raf.seek(sptr);
raf.readFully(iBuffer, 0, iBuffer.Length);
l = 0; h = blockLen / blen;
long sip, eip, dataptr = 0;
while (l <= h)
{
int m = (l + h) >> 1;
int p = m * blen;
sip = Util.getIntLong(iBuffer, p);
if (ip < sip)
{
h = m - 1;
}
else
{
eip = Util.getIntLong(iBuffer, p + 4);
if (ip > eip)
{
l = m + 1;
}
else
{
dataptr = Util.getIntLong(iBuffer, p + 8);
break;
}
}
}
//not matched
if (dataptr == 0)
{
return(null);
}
//3. get the data
int dataLen = (int)((dataptr >> 24) & 0xFF);
int dataPtr = (int)((dataptr & 0x00FFFFFF));
raf.seek(dataPtr);
byte[] data = new byte[dataLen];
raf.readFully(data, 0, data.Length);
int city_id = (int)Util.getIntLong(data, 0);
//String region = new String(data, 4, data.Length - 4, "UTF-8");
var region = Encoding.UTF8.GetString(data, 4, data.Length);
return(new DataBlock(city_id, region, dataPtr));
}