/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2002,2008 Oracle.  All rights reserved.
 *
 * $Id: ChecksumValidator.java,v 1.36 2008/01/17 17:36:20 cwl Exp $
 */

package com.sleepycat.je.log;

import java.nio.ByteBuffer;
import java.util.zip.Checksum;

import com.sleepycat.je.dbi.EnvironmentImpl;
import com.sleepycat.je.utilint.Adler32;
import com.sleepycat.je.utilint.DbLsn;

/**
 * Checksum validator is used to check checksums on log entries.
 */
class ChecksumValidator {
    private static final boolean DEBUG = false;

    private Checksum cksum;

    ChecksumValidator() {
        cksum = Adler32.makeChecksum();
    }

    void reset() {
        cksum.reset();
    }

    /**
     * Add this byte buffer to the checksum. Assume the byte buffer is already
     * positioned at the data.
     * @param buf target buffer
     * @param length of data
     */
    void update(EnvironmentImpl env,
		ByteBuffer buf,
		int length,
		boolean anticipateChecksumErrors)
        throws DbChecksumException {

        if (buf == null) {
            throw new DbChecksumException
		((anticipateChecksumErrors ? null : env),
		 "null buffer given to checksum validation, probably " +
		 " result of 0's in log file. " + anticipateChecksumErrors);
        }

        int bufStart = buf.position();

        if (DEBUG) {
	    System.out.println("bufStart = " + bufStart +
			       " length = " + length);
        }

        if (buf.hasArray()) {
            cksum.update(buf.array(), bufStart + buf.arrayOffset(), length);
        } else {
            for (int i = bufStart; i < (length + bufStart); i++) {
                cksum.update(buf.get(i));
            }
        }
    }

    void validate(EnvironmentImpl env,
                  long expectedChecksum,
                  long lsn)
        throws DbChecksumException {

        if (expectedChecksum != cksum.getValue()) {
            throw new DbChecksumException
		(env,
		 "Location " + DbLsn.getNoFormatString(lsn) +
		 " expected " + expectedChecksum + " got " + cksum.getValue());
        }
    }

    void validate(EnvironmentImpl env,
                  long expectedChecksum,
                  long fileNum,
                  long fileOffset,
		  boolean anticipateChecksumErrors)
        throws DbChecksumException {

        if (expectedChecksum != cksum.getValue()) {
            long problemLsn = DbLsn.makeLsn(fileNum, fileOffset);

	    /*
	     * Pass null for env so that RunRecoveryException() does not
	     * invalidate the environment.
	     */
            throw new DbChecksumException
		((anticipateChecksumErrors ? null : env),
		 "Location " + DbLsn.getNoFormatString(problemLsn) +
		 " expected " + expectedChecksum + " got " +
		 cksum.getValue());
        }
    }
}
