/**
* Remove the value which is associated with the given key. If the key does not exist, this method
* simply ignores the operation.
*
* @param key key whose associated value is to be removed
* @return object which was associated with the given key, or <code>null</code> if no association
* existed with given key.
*/
Object remove(Object key) throws IOException {
int hash = hashCode(key);
long child_recid = _children[hash];
if (child_recid == 0) {
// not bucket/page --> not found
return null;
} else {
HashNode node = (HashNode) _recman.fetch(child_recid, tree.SERIALIZER);
// System.out.println("HashDirectory.remove() child is : "+node);
if (node instanceof HashDirectory) {
// recurse into next directory level
HashDirectory dir = (HashDirectory) node;
dir.setPersistenceContext(_recman, child_recid);
Object existing = dir.remove(key);
if (existing != null) {
if (dir.isEmpty()) {
// delete empty directory
_recman.delete(child_recid);
_children[hash] = 0;
_recman.update(_recid, this, tree.SERIALIZER);
}
}
return existing;
} else {
// node is a bucket
HashBucket bucket = (HashBucket) node;
Object existing = bucket.removeElement(key);
if (existing != null) {
if (bucket.getElementCount() >= 1) {
_recman.update(child_recid, bucket, tree.SERIALIZER);
} else {
// delete bucket, it's empty
_recman.delete(child_recid);
_children[hash] = 0;
_recman.update(_recid, this, tree.SERIALIZER);
}
}
return existing;
}
}
}
/**
* Returns the value which is associated with the given key. Returns <code>null</code> if there is
* not association for this key.
*
* @param key key whose associated value is to be returned
*/
V get(K key) throws IOException {
int hash = hashCode(key);
long child_recid = _children[hash];
if (child_recid == 0) {
// not bucket/page --> not found
return null;
} else {
HashNode<K, V> node = (HashNode<K, V>) _recman.fetch(child_recid, tree.SERIALIZER);
// System.out.println("HashDirectory.get() child is : "+node);
if (node instanceof HashDirectory) {
// recurse into next directory level
HashDirectory<K, V> dir = (HashDirectory<K, V>) node;
dir.setPersistenceContext(_recman, child_recid);
return dir.get(key);
} else {
// node is a bucket
HashBucket<K, V> bucket = (HashBucket) node;
return bucket.getValue(key);
}
}
}
/**
* Associates the specified value with the specified key.
*
* @param key key with which the specified value is to be assocated.
* @param value value to be associated with the specified key.
* @return object which was previously associated with the given key, or <code>null</code> if no
* association existed.
*/
Object put(Object key, Object value) throws IOException {
if (value == null) {
return remove(key);
}
int hash = hashCode(key);
long child_recid = _children[hash];
if (child_recid == 0) {
// no bucket/page here yet, let's create a bucket
HashBucket bucket = new HashBucket(tree, _depth + 1);
// insert (key,value) pair in bucket
Object existing = bucket.addElement(key, value);
long b_recid = _recman.insert(bucket, tree.SERIALIZER);
_children[hash] = b_recid;
_recman.update(_recid, this, tree.SERIALIZER);
// System.out.println("Added: "+bucket);
return existing;
} else {
HashNode node = (HashNode) _recman.fetch(child_recid, tree.SERIALIZER);
if (node instanceof HashDirectory) {
// recursive insert in next directory level
HashDirectory dir = (HashDirectory) node;
dir.setPersistenceContext(_recman, child_recid);
return dir.put(key, value);
} else {
// node is a bucket
HashBucket bucket = (HashBucket) node;
if (bucket.hasRoom()) {
Object existing = bucket.addElement(key, value);
_recman.update(child_recid, bucket, tree.SERIALIZER);
// System.out.println("Added: "+bucket);
return existing;
} else {
// overflow, so create a new directory
if (_depth == MAX_DEPTH) {
throw new RuntimeException("Cannot create deeper directory. " + "Depth=" + _depth);
}
HashDirectory dir = new HashDirectory(tree, (byte) (_depth + 1));
long dir_recid = _recman.insert(dir, tree.SERIALIZER);
dir.setPersistenceContext(_recman, dir_recid);
_children[hash] = dir_recid;
_recman.update(_recid, this, tree.SERIALIZER);
// discard overflown bucket
_recman.delete(child_recid);
// migrate existing bucket elements
ArrayList keys = bucket.getKeys();
ArrayList values = bucket.getValues();
int entries = keys.size();
for (int i = 0; i < entries; i++) {
dir.put(keys.get(i), values.get(i));
}
// (finally!) insert new element
return dir.put(key, value);
}
}
}
}