private Bucket SetBucket(byte[] key, int offset, Bucket b)
{
bool found = false;
int pos = FindPointerOrLower(b, new bytearr(key), out found);
if (found)
{
KeyPointer p = b.Pointers[pos];
int v = p.RecordNum;
// duplicate found
if (v != offset)
{
p.RecordNum = offset;
DirtyBucket(b);
}
}
else
{
if (b.Pointers.Count < _bucketItems)
{
KeyPointer k = new KeyPointer(new bytearr(key), offset);
pos++;
if (pos < b.Pointers.Count)
b.Pointers.Insert(pos, k);
else
b.Pointers.Add(k);
DirtyBucket(b);
}
else
{
int p = b.NextPageNumber;
if (p != -1)
{
b = LoadBucket(p);
SetBucket(key, offset, b);
}
else
{
Bucket newb = new Bucket(_indexfile.GetNewPageNumber());
b.NextPageNumber = newb.DiskPageNumber;
DirtyBucket(b);
SetBucket(key, offset, newb);
}
}
}
return b;
}
public Bucket LoadBucketFromPage(int page)
{
SeekPage(page);
byte[] b = new byte[_PageLength];
_file.Read(b, 0, _PageLength);
if (b[0] == _BlockHeader[0] && b[1] == _BlockHeader[1] && b[2] == _BlockHeader[2] && b[3] == _BlockHeader[3])
{
// create node here
int bucketnum = Helper.ToInt32(b, 7);
List<KeyPointer> list = new List<KeyPointer>();
List<int> dups = new List<int>();
short count = Helper.ToInt16(b, 5);
if (count > _PageNodeCount)
throw new Exception("Count > node size");
int nextpage = Helper.ToInt32(b, 11);
int index = _BlockHeader.Length;
if ((b[4] & 4) == 4)
{
int dupc = Helper.ToInt32(b, index);
index += 4;
for (int i = 0; i < dupc; i++)
{
int l = Helper.ToInt32(b, index);
dups.Add(l);
index += 4;
}
}
else
{
for (int i = 0; i < count; i++)
{
int idx = index + _rowSize*i;
byte ks = b[idx];
byte[] key = new byte[ks];
Buffer.BlockCopy(b, idx + 1, key, 0, ks);
int offset = Helper.ToInt32(b, idx + 1 + _maxKeySize);
int duppage = Helper.ToInt32(b, idx + 1 + _maxKeySize + 4);
KeyPointer kp = new KeyPointer(new bytearr(key), offset, duppage);
list.Add(kp);
}
}
Bucket n = new Bucket(b[4], bucketnum, list, dups, page, nextpage);
return n;
}
throw new Exception("Page read error");
}
public void SaveBucket(Bucket bucket)
{
int pnum = bucket.DiskPageNumber;
if (pnum > _LastPageNumber)
throw new Exception("should not be here: page out of bounds");
SeekPage(pnum);
byte[] page = new byte[_PageLength];
Buffer.BlockCopy(_BlockHeader, 0, page, 0, _BlockHeader.Length);
// bucket type
if (bucket.isBucket)
page[4] = 8;
if (bucket.isOverflow)
page[4] += 16;
// bucket count
byte[] b = Helper.GetBytes(bucket.Count, false);
Buffer.BlockCopy(b, 0, page, 5, b.Length);
// bucket number
b = Helper.GetBytes(bucket.BucketNumber, false);
Buffer.BlockCopy(b, 0, page, 7, b.Length);
// next page number
b = Helper.GetBytes(bucket.NextPageNumber, false);
Buffer.BlockCopy(b, 0, page, 11, b.Length);
int index = _BlockHeader.Length;
if (bucket.isOverflow == true)
{
b = Helper.GetBytes(bucket.Duplicates.Count, false);
Buffer.BlockCopy(b, 0, page, index, b.Length);
index += b.Length;
foreach (long p in bucket.Duplicates)
{
b = Helper.GetBytes(p, false);
Buffer.BlockCopy(b, 0, page, index, b.Length);
index += b.Length;
}
}
else
{
// bucket children
for (int i = 0; i < bucket.Count; i++)
{
KeyPointer kp = bucket.Pointers[i];
int idx = index + _rowSize*i;
byte size = (byte) kp.Key.val.Length;
if (size > _maxKeySize)
size = _maxKeySize;
// key size = 1 byte
page[idx] = size;
// key bytes
Buffer.BlockCopy(bucket.Pointers[i].Key.val, 0, page, idx + 1, page[idx]);
// offset = 4 bytes
b = Helper.GetBytes(kp.RecordNum, false);
Buffer.BlockCopy(b, 0, page, idx + 1 + _maxKeySize, b.Length);
// duplicatepage = 4 bytes
b = Helper.GetBytes(kp.DuplicatesPage, false);
Buffer.BlockCopy(b, 0, page, idx + 1 + _maxKeySize + 4, b.Length);
}
}
bucket.isOverflow = false;
_file.Write(page, 0, page.Length);
_file.Flush();
}
private Bucket CreateBucket(int bucketNumber)
{
var b = new Bucket(_indexfile.GetNewPageNumber()) {BucketNumber = bucketNumber};
// get next free indexfile pointer offset
return b;
}
private int FindPointerOrLower(Bucket b, bytearr key, out bool found)
{
found = false;
if (b.Pointers.Count == 0)
return 0;
// binary search
int lastlower = -1;
int first = 0;
int last = b.Pointers.Count - 1;
int mid = 0;
while (first <= last)
{
mid = (first + last) >> 1;
KeyPointer k = b.Pointers[mid];
int compare = Helper.Compare(k.Key, key);
if (compare < 0)
{
lastlower = mid;
first = mid + 1;
}
if (compare == 0)
{
found = true;
return mid;
}
if (compare > 0)
{
last = mid - 1;
}
}
return lastlower;
}
private void DirtyBucket(Bucket b)
{
if (b.isDirty)
return;
b.isDirty = true;
if (_cachedBuckets.ContainsKey(b.DiskPageNumber) == false)
_cachedBuckets.Add(b.DiskPageNumber, b);
}
private bool SearchBucket(Bucket b, byte[] key, ref int offset)
{
bool found = false;
int pos = FindPointerOrLower(b, new bytearr(key), out found);
if (found)
{
KeyPointer k = b.Pointers[pos];
offset = k.RecordNum;
return true;
}
else
{
if (b.NextPageNumber != -1)
{
b = LoadBucket(b.NextPageNumber);
return SearchBucket(b, key, ref offset);
}
}
return false;
}