org.h2.store.DataHandler Maven / Gradle / Ivy
/*
* Copyright 2004-2014 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.store;
import org.h2.api.JavaObjectSerializer;
import org.h2.message.DbException;
import org.h2.util.SmallLRUCache;
import org.h2.util.TempFileDeleter;
import org.h2.value.CompareMode;
/**
* A data handler contains a number of callback methods, mostly related to CLOB
* and BLOB handling. The most important implementing class is a database.
*/
public interface DataHandler {
/**
* Get the database path.
*
* @return the database path
*/
String getDatabasePath();
/**
* Open a file at the given location.
*
* @param name the file name
* @param mode the mode
* @param mustExist whether the file must already exist
* @return the file
*/
FileStore openFile(String name, String mode, boolean mustExist);
/**
* Check if the simulated power failure occurred.
* This call will decrement the countdown.
*
* @throws DbException if the simulated power failure occurred
*/
void checkPowerOff() throws DbException;
/**
* Check if writing is allowed.
*
* @throws DbException if it is not allowed
*/
void checkWritingAllowed() throws DbException;
/**
* Get the maximum length of a in-place large object
*
* @return the maximum size
*/
int getMaxLengthInplaceLob();
/**
* Get the compression algorithm used for large objects.
*
* @param type the data type (CLOB or BLOB)
* @return the compression algorithm, or null
*/
String getLobCompressionAlgorithm(int type);
/**
* Get the temp file deleter mechanism.
*
* @return the temp file deleter
*/
TempFileDeleter getTempFileDeleter();
/**
* Get the synchronization object for lob operations.
*
* @return the synchronization object
*/
Object getLobSyncObject();
/**
* Get the lob file list cache if it is used.
*
* @return the cache or null
*/
SmallLRUCache getLobFileListCache();
/**
* Get the lob storage mechanism to use.
*
* @return the lob storage mechanism
*/
LobStorageInterface getLobStorage();
/**
* Read from a lob.
*
* @param lobId the lob id
* @param hmac the message authentication code
* @param offset the offset within the lob
* @param buff the target buffer
* @param off the offset within the target buffer
* @param length the number of bytes to read
* @return the number of bytes read
*/
int readLob(long lobId, byte[] hmac, long offset, byte[] buff, int off,
int length);
/**
* Return the serializer to be used for java objects being stored in
* column of type OTHER.
*
* @return the serializer to be used for java objects being stored in
* column of type OTHER
*/
JavaObjectSerializer getJavaObjectSerializer();
/**
* Return compare mode.
*
* @return Compare mode.
*/
CompareMode getCompareMode();
}