public B_Tree.Page<Key> load(int pageNo) {
try {
ByteBuffer buffer = ByteBuffer.allocate(pageSize);
channel.read(buffer, pageNo * pageSize);
buffer.rewind();
B_Tree.Page<Key> page = new B_Tree.Page<Key>(pageNo);
List<B_Tree.KeyPointer<Key>> keyPointers = page.keyPointers;
char nodeType = buffer.getChar();
int size = buffer.getInt();
for (int i = 0; i < size; i++) {
Key key = keyAccessor.read(buffer);
if (nodeType == INTERNAL) {
int branch = buffer.getInt();
addBranch(keyPointers, key, branch);
} else if (nodeType == LEAF) {
Value value = valueAccessor.read(buffer);
addLeaf(keyPointers, key, value);
}
}
return page;
} catch (IOException ex) {
throw new RuntimeException(ex);
}
}
public void save(int pageNo, B_Tree.Page<Key> page) {
try {
ByteBuffer buffer = ByteBuffer.allocate(pageSize);
List<B_Tree.KeyPointer<Key>> ptrs = page.keyPointers;
boolean isBranch = !ptrs.isEmpty() && ptrs.get(0).t2 instanceof B_Tree.Branch;
buffer.putChar(isBranch ? INTERNAL : LEAF);
buffer.putInt(ptrs.size());
for (B_Tree.KeyPointer<Key> keyPtr : ptrs) {
keyAccessor.write(buffer, keyPtr.t1);
if (keyPtr.t2 instanceof B_Tree.Branch) {
int branch = ((B_Tree.Branch) keyPtr.t2).branch;
buffer.putInt(branch);
} else if (keyPtr.t2 instanceof B_Tree.Leaf) {
@SuppressWarnings("unchecked")
Value value = ((B_Tree.Leaf<Value>) keyPtr.t2).value;
valueAccessor.write(buffer, value);
}
}
buffer.flip();
channel.write(buffer, pageNo * pageSize);
} catch (IOException ex) {
throw new RuntimeException(ex);
}
}
