A B+Tree with many features.

At the moment, the on-disk format is NOT stable. It will almost certainly change in the future. Please do not use the BTree to store data across invocations of the JVM.

At the moment, the BTree does not support deleting or replacing values.

There are three kinds of classes in this package:

- The {@see com.sun.electric.database.geometry.btree.BTree}<K,V,S> class itself, which provides the B+Tree data structure parameterized over a key type (K), value type (V), and optional summary (see below) type (S).
- Subclasses of {@see com.sun.electric.database.geometry.btree.NodeCursor}, which are package-private. These act like smart "pointers" to individual pages within the BTree and help to simplify BTree.java.
- The {@see com.sun.electric.database.geometry.btree.PageStorage} class and subclasses. A PageStorage is sort of like a `HashMap<Integer,byte[]>` with a few extra features and restrictions. A CachingPageStorage is like a PageStorage that lets you write directly to the byte[]'s that are resident in memory.

The subpackage unboxed provides "unboxed" versions of many data structures; please take a brief look at it first.