/**
* Load a persistent BTree.
*
* @param recman RecordManager used to store the persistent btree
* @param recid Record id of the BTree
*/
public static BTree load(RecordManager recman, long recid) throws IOException {
BTree btree = (BTree) recman.fetch(recid);
btree._recid = recid;
btree._recman = recman;
btree._bpageSerializer = new BPage();
btree._bpageSerializer._btree = btree;
return btree;
}
/**
* Create a new persistent BTree with the given number of entries per node.
*
* @param recman Record manager used for persistence.
* @param comparator Comparator used to order index entries
* @param keySerializer Serializer used to serialize index keys (optional)
* @param valueSerializer Serializer used to serialize index values (optional)
* @param pageSize Number of entries per page (must be even).
*/
public static BTree createInstance(
RecordManager recman,
Comparator comparator,
Serializer keySerializer,
Serializer valueSerializer,
int pageSize)
throws IOException {
BTree btree;
if (recman == null) {
throw new IllegalArgumentException("Argument 'recman' is null");
}
if (comparator == null) {
throw new IllegalArgumentException("Argument 'comparator' is null");
}
if (!(comparator instanceof Serializable)) {
throw new IllegalArgumentException("Argument 'comparator' must be serializable");
}
if (keySerializer != null && !(keySerializer instanceof Serializable)) {
throw new IllegalArgumentException("Argument 'keySerializer' must be serializable");
}
if (valueSerializer != null && !(valueSerializer instanceof Serializable)) {
throw new IllegalArgumentException("Argument 'valueSerializer' must be serializable");
}
// make sure there's an even number of entries per BPage
if ((pageSize & 1) != 0) {
throw new IllegalArgumentException("Argument 'pageSize' must be even");
}
btree = new BTree();
btree._recman = recman;
btree._comparator = comparator;
btree._keySerializer = keySerializer;
btree._valueSerializer = valueSerializer;
btree._pageSize = pageSize;
btree._bpageSerializer = new BPage();
btree._bpageSerializer._btree = btree;
btree._recid = recman.insert(btree);
return btree;
}