suneido.database.immudb.DbGood.java Source code

Introduction

Here is the source code for suneido.database.immudb.DbGood.java

Source

/* Copyright 2015 (c) Suneido Software Corp. All rights reserved.
 * Licensed under GPLv2.
 */

package suneido.database.immudb;

import java.io.File;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import com.google.common.primitives.Longs;

import suneido.util.Errlog;

/**
 * jSuneido checks the database at startup.
 * It normally does a fast check of the last part of the database.
 * But if the database is not shut down properly,
 * or signs of corruption are detected,
 * then next time it starts we want to do a full check.
 * To record that the database was shut down properly
 * a file (suneido.dbc) is written containing a hash of the database size.
 * At startup we check this file.
 * So if we crash after writing to the db then we'll do a full check.
 * If the db isn't modified then the size will stay the same
 * and we don't need a full check even if we crash.
 */
public class DbGood {

    public static void create(String filename, long size) {
        try {
            Files.write(Paths.get(filename), hash(size));
        } catch (Throwable e) {
            Errlog.error("DbGood.create", e);
        }
    }

    public static boolean check(String filename, long size) {
        try {
            return new File(filename).canRead()
                    && Arrays.equals(hash(size), Files.readAllBytes(Paths.get(filename)));
        } catch (Throwable e) {
            Errlog.error("DbGood.check", e);
            return false;
        }
    }

    private static byte[] hash(long size) throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA-1");
        md.update(Longs.toByteArray(size));
        return md.digest();
    }

}