table/builder.go
func (b Builder) keyDiff(newKey []byte) []byte {
	var i int
	for i = 0; i < len(newKey) && i < len(b.baseKey); i++ {
		if newKey[i] != b.baseKey[i] {
			break
		}
	}
	return newKey[i:]
}
func (b Builder) keyDiff(newKey []byte) []byte {
	var i int
	for i = 0; i < len(newKey) && i < len(b.baseKey); i++ {
		if newKey[i] != b.baseKey[i] {
			break
		}
	}
	return newKey[i:]
}
// keyDiff returns a suffix of newKey that is different from b.baseKey.