com.mckoi.store

Class JournalledFileStore

java.lang.Object

com.mckoi.store.AbstractStore

com.mckoi.store.JournalledFileStore

All Implemented Interfaces:

Store

public final class JournalledFileStore
extends AbstractStore

An implementation of AbstractStore that persists to an underlying data format via a robust journalling system that supports check point and crash recovery. Note that this object is a bridge between the Store API and the journalled behaviour defined in LoggingBufferManager, JournalledSystem and the StoreDataAccessor implementations.

Note that access to the resources is abstracted via a 'resource_name' string. The LoggingBufferManager object converts the resource name into a concrete object that accesses the actual data.

Author:

Tobias Downer

Field Summary

Fields inherited from class com.mckoi.store.AbstractStore

BIN_AREA_OFFSET, BIN_ENTRIES, DATA_AREA_OFFSET, FIXED_AREA_OFFSET, free_bin_list, header_buf, MAGIC, read_only, total_allocated_space, wilderness_pointer

Constructor Summary

Constructors

Constructor and Description
JournalledFileStore(String resource_name, LoggingBufferManager buffer_manager, boolean read_only) Constructs the ScatteringFileStore.

Method Summary

Modifier and Type	Method and Description
boolean	delete() Deletes this store from the file system.
protected long	endOfDataAreaPointer() Returns a pointer to the end of the current data area.
boolean	exists() Returns true if this store exists in the file system.
protected void	internalClose() Internally closes the backing area.
protected void	internalOpen(boolean read_only) Internally opens the backing area.
void	lockForWrite() It is often useful to guarentee that a certain sequence of updates to a store is completed and not broken in the middle.
protected int	readByteArrayFrom(long position, byte[] buf, int off, int len) Reads a byte array from the given position in the file.
protected int	readByteFrom(long position) Reads a byte from the given position in the file.
protected void	setDataAreaSize(long new_size) Sets the size of the data area.
String	toString()
void	unlockForWrite() See the 'lockForWrite' method description.
protected void	writeByteArrayTo(long position, byte[] buf, int off, int len) Writes a byte array to the given position in the file.
protected void	writeByteTo(long position, int b) Writes a byte to the given position in the file.

Methods inherited from class com.mckoi.store.AbstractStore

checkPointer, close, coalescArea, createArea, deleteArea, expandDataArea, findAllocatedAreasNotIn, getAllAreas, getArea, getAreaHeader, getAreaInputStream, getMutableArea, getNextAreaHeader, getPreviousAreaHeader, isValidBoundarySize, lastCloseClean, open, openScanAndFix, readBins, reboundArea, splitArea, statsScan, totalAllocatedSinceStart, writeAllBins, writeBinIndex

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

JournalledFileStore

public JournalledFileStore(String resource_name,
                           LoggingBufferManager buffer_manager,
                           boolean read_only)

Constructs the ScatteringFileStore.

Method Detail

delete

public boolean delete()
               throws IOException

Deletes this store from the file system. This operation should only be used when the store is NOT open.

Throws:

IOException

exists

public boolean exists()
               throws IOException

Returns true if this store exists in the file system.

Throws:

IOException

lockForWrite

public void lockForWrite()

Description copied from interface: Store

It is often useful to guarentee that a certain sequence of updates to a store is completed and not broken in the middle. For example, when inserting data into a table you don't want a record to be partially written when a check point is made. You want the entire sequence of modifications to be completed before the check point can run. This means that if a crash occurs, a check point will not recover to a possible corrupt file.

To achieve this, the 'lockForWrite' and 'unlockForWrite' methods are available. When 'lockForWrite' has been called, a check point can not created until there are no write locks obtained on the table.

unlockForWrite

public void unlockForWrite()

Description copied from interface: Store

See the 'lockForWrite' method description.

internalOpen

protected void internalOpen(boolean read_only)
                     throws IOException

Internally opens the backing area. If 'read_only' is true then the store is opened in read only mode.

Specified by:

internalOpen in class AbstractStore

Throws:

IOException

internalClose

protected void internalClose()
                      throws IOException

Internally closes the backing area.

Specified by:

internalClose in class AbstractStore

Throws:

IOException

readByteFrom

protected int readByteFrom(long position)
                    throws IOException

Description copied from class: AbstractStore

Reads a byte from the given position in the file.

Specified by:

readByteFrom in class AbstractStore

Throws:

IOException

readByteArrayFrom

protected int readByteArrayFrom(long position,
                                byte[] buf,
                                int off,
                                int len)
                         throws IOException

Description copied from class: AbstractStore

Reads a byte array from the given position in the file. Returns the number of bytes read.

Specified by:

readByteArrayFrom in class AbstractStore

Throws:

IOException

writeByteTo

protected void writeByteTo(long position,
                           int b)
                    throws IOException

Description copied from class: AbstractStore

Writes a byte to the given position in the file.

Specified by:

writeByteTo in class AbstractStore

Throws:

IOException

writeByteArrayTo

protected void writeByteArrayTo(long position,
                                byte[] buf,
                                int off,
                                int len)
                         throws IOException

Description copied from class: AbstractStore

Writes a byte array to the given position in the file.

Specified by:

writeByteArrayTo in class AbstractStore

Throws:

IOException

endOfDataAreaPointer

protected long endOfDataAreaPointer()
                             throws IOException

Description copied from class: AbstractStore

Returns a pointer to the end of the current data area.

Specified by:

endOfDataAreaPointer in class AbstractStore

Throws:

IOException

setDataAreaSize

protected void setDataAreaSize(long new_size)
                        throws IOException

Description copied from class: AbstractStore

Sets the size of the data area.

Specified by:

setDataAreaSize in class AbstractStore

Throws:

IOException

toString

public String toString()

Overrides:

toString in class Object