func ReadDatabaseVersion(db DatabaseReader) *uint64 {
	var version uint64
	enc, _ := db.Get(databaseVerisionKey)
	if len(enc) == 0 {
		return nil
	}
	if err := rlp.DecodeBytes(enc, &version); err != nil {
		return nil
	}
	return &version
}
ReadDatabaseVersion retrieves the version number of the database.
package rawdb
import (
	"encoding/json"
	"github.com/dappledger/AnnChain/eth/common"
	"github.com/dappledger/AnnChain/eth/log"
	"github.com/dappledger/AnnChain/eth/params"
	"github.com/dappledger/AnnChain/eth/rlp"
)