/**
* Creates a new root block for the B-tree. The new root will have two children: the old root, and
* the specified block. Since the root must always be in block 0 of the file, the contents of the
* old root will get transferred to a new block.
*
* @param e the directory entry to be added as a child of the new root
*/
public void makeNewRoot(DirEntry e) {
Constant firstval = contents.getDataVal(0);
int level = contents.getFlag();
Block newblk = contents.split(0, level); // ie, transfer all the records
DirEntry oldroot = new DirEntry(firstval, newblk.number());
insertEntry(oldroot);
insertEntry(e);
contents.setFlag(level + 1);
}
private DirEntry insertEntry(DirEntry e) {
int newslot = 1 + contents.findSlotBefore(e.dataVal());
contents.insertDir(newslot, e.dataVal(), e.blockNumber());
if (!contents.isFull()) return null;
// else page is full, so split it
int level = contents.getFlag();
int splitpos = contents.getNumRecs() / 2;
Constant splitval = contents.getDataVal(splitpos);
Block newblk = contents.split(splitpos, level);
return new DirEntry(splitval, newblk.number());
}
private Block findChildBlock(Constant searchkey) {
int slot = contents.findSlotBefore(searchkey);
if (contents.getDataVal(slot + 1).equals(searchkey)) slot++;
int blknum = contents.getChildNum(slot);
return new Block(filename, blknum);
}