Database

Responsible for database operations. This module is where the blockchain's state persistence is managed. The module defines three primary traits (Database, DatabaseCommit, and DatabaseRef), a structure RefDBWrapper, and their associated methods.

The Database trait defines an interface for mutable interaction with the database. It has a generic associated type Error to handle different kinds of errors that might occur during these interactions. It provides methods to retrieve basic account information (basic), retrieve account code by its hash (code_by_hash), retrieve the storage value of an address at a certain index (storage), and retrieve the block hash for a certain block number (block_hash).

The DatabaseCommit trait defines a single commit method for committing changes to the database. The changes are a map between Ethereum-like addresses (type Address) and accounts.

The DatabaseRef trait is similar to the Database trait but is designed for read-only or immutable interactions. It has the same Error associated type and the same set of methods as Database, but these methods take &self instead of &mut self, indicating that they do not mutate the database.

The RefDBWrapper structure is a wrapper around a reference to a DatabaseRef type. It implements the Database trait, essentially providing a way to treat a DatabaseRef as a Database by forwarding the Database methods to the corresponding DatabaseRef methods.