/** * 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); } } } }