com.healthmarketscience.jackcess.impl
Class PageChannel

java.lang.Object
  com.healthmarketscience.jackcess.impl.PageChannel

All Implemented Interfaces:

Closeable, Flushable, Channel

public class PageChannel
extends Object
implements Channel, Flushable

Reads and writes individual pages in a database file

Author:

Tim McCune

Constructor Summary

PageChannel(FileChannel channel, boolean closeChannel, JetFormat format, boolean autoSync)

Method Summary

int	allocateNewPage() Allocates a new page in the database.
void	close()
static ByteBuffer	createBuffer(int size)
static ByteBuffer	createBuffer(int size, ByteOrder order)
ByteBuffer	createPageBuffer()
void	deallocatePage(int pageNumber) Deallocate a previously used page in the database.
void	finishWrite() Completes a "logical" write operation.
void	flush()
JetFormat	getFormat()
void	initialize(DatabaseImpl database, CodecProvider codecProvider) Does second-stage initialization, must be called after construction.
boolean	isAutoSync()
boolean	isOpen()
boolean	isWriting() Returns true if a logical write operation is in progress, false otherwise.
static ByteBuffer	narrowBuffer(ByteBuffer buffer, int position, int limit)
void	readPage(ByteBuffer buffer, int pageNumber)
void	startWrite() Begins a "logical" write operation.
static ByteBuffer	wrap(byte[] bytes) Returns a ByteBuffer wrapping the given bytes and configured with the default byte order.
void	writePage(ByteBuffer page, int pageNumber) Write a page to disk
void	writePage(ByteBuffer page, int pageNumber, int pageOffset) Write a page (or part of a page) to disk

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PageChannel

public PageChannel(FileChannel channel,
                   boolean closeChannel,
                   JetFormat format,
                   boolean autoSync)
            throws IOException

Parameters:

channel - Channel containing the database

format - Format of the database in the channel

Throws:

IOException

Method Detail

initialize

public void initialize(DatabaseImpl database,
                       CodecProvider codecProvider)
                throws IOException

Does second-stage initialization, must be called after construction.

Throws:

IOException

getFormat

public JetFormat getFormat()

isAutoSync

public boolean isAutoSync()

startWrite

public void startWrite()

Begins a "logical" write operation. See finishWrite() for more details.

finishWrite

public void finishWrite()
                 throws IOException

Completes a "logical" write operation. This method should be called in finally block which wraps a logical write operation (which is preceded by a startWrite() call). Logical write operations may be nested. If the database is configured for "auto-sync", the channel will be flushed when the outermost operation is complete,

Throws:

IOException

isWriting

public boolean isWriting()

Returns true if a logical write operation is in progress, false otherwise.

readPage

public void readPage(ByteBuffer buffer,
                     int pageNumber)
              throws IOException

Parameters:

buffer - Buffer to read the page into

pageNumber - Number of the page to read in (starting at 0)

Throws:

IOException

writePage

public void writePage(ByteBuffer page,
                      int pageNumber)
               throws IOException

Write a page to disk

Parameters:

page - Page to write

pageNumber - Page number to write the page to

Throws:

IOException

writePage

public void writePage(ByteBuffer page,
                      int pageNumber,
                      int pageOffset)
               throws IOException

Write a page (or part of a page) to disk

Parameters:

page - Page to write

pageNumber - Page number to write the page to

pageOffset - offset within the page at which to start writing the page data

Throws:

IOException

allocateNewPage

public int allocateNewPage()
                    throws IOException

Allocates a new page in the database. Data in the page is undefined until it is written in a call to writePage(ByteBuffer,int).

Throws:

IOException

deallocatePage

public void deallocatePage(int pageNumber)
                    throws IOException

Deallocate a previously used page in the database.

Throws:

IOException

createPageBuffer

public ByteBuffer createPageBuffer()

Returns:

A newly-allocated buffer that can be passed to readPage

createBuffer

public static ByteBuffer createBuffer(int size)

Returns:

A newly-allocated buffer of the given size and DEFAULT_BYTE_ORDER byte order

createBuffer

public static ByteBuffer createBuffer(int size,
                                      ByteOrder order)

Returns:

A newly-allocated buffer of the given size and byte order

flush

public void flush()
           throws IOException

Specified by:

flush in interface Flushable

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface Channel

Throws:

IOException

isOpen

public boolean isOpen()

Specified by:

isOpen in interface Channel

narrowBuffer

public static ByteBuffer narrowBuffer(ByteBuffer buffer,
                                      int position,
                                      int limit)

Returns:

a duplicate of the current buffer narrowed to the given position and limit. mark will be set at the current position.

wrap

public static ByteBuffer wrap(byte[] bytes)

Returns a ByteBuffer wrapping the given bytes and configured with the default byte order.