Add database iteration to restricted backend

Needed for cardinal state dump

restricted/database.go

@@ -123,5 +123,51 @@ type Database interface {
 	Writer
 	Stater
 	Compacter
+	Iteratee
 	io.Closer
 }
+
+
+// Iterator iterates over a database's key/value pairs in ascending key order.
+//
+// When it encounters an error any seek will return false and will yield no key/
+// value pairs. The error can be queried by calling the Error method. Calling
+// Release is still necessary.
+//
+// An iterator must be released after use, but it is not necessary to read an
+// iterator until exhaustion. An iterator is not safe for concurrent use, but it
+// is safe to use multiple iterators concurrently.
+type Iterator interface {
+	// Next moves the iterator to the next key/value pair. It returns whether the
+	// iterator is exhausted.
+	Next() bool
+
+	// Error returns any accumulated error. Exhausting all the key/value pairs
+	// is not considered to be an error.
+	Error() error
+
+	// Key returns the key of the current key/value pair, or nil if done. The caller
+	// should not modify the contents of the returned slice, and its contents may
+	// change on the next call to Next.
+	Key() []byte
+
+	// Value returns the value of the current key/value pair, or nil if done. The
+	// caller should not modify the contents of the returned slice, and its contents
+	// may change on the next call to Next.
+	Value() []byte
+
+	// Release releases associated resources. Release should always succeed and can
+	// be called multiple times without causing error.
+	Release()
+}
+
+// Iteratee wraps the NewIterator methods of a backing data store.
+type Iteratee interface {
+	// NewIterator creates a binary-alphabetical iterator over a subset
+	// of database content with a particular key prefix, starting at a particular
+	// initial key (or after, if it does not exist).
+	//
+	// Note: This method assumes that the prefix is NOT part of the start, so there's
+	// no need for the caller to prepend the prefix to the start
+	NewIterator(prefix []byte, start []byte) Iterator
+}