Package org.aksw.commons.io.block.impl

Class PageManagerForFileChannel

java.lang.Object

org.aksw.commons.io.block.impl.PageManagerForFileChannel

All Implemented Interfaces:

BlockSource, PageManager

public class PageManagerForFileChannel
extends Object
implements PageManager

Field Summary

Fields

Modifier and Type	Field	Description
protected FileChannel	channel
protected long	channelSize	We rely on the channel's size being constant.
static final int	DEFAULT_PAGE_SIZE
protected com.google.common.cache.Cache<Long,org.aksw.commons.util.ref.Ref<Page>>	pageCache	The cache is crucial to the implementation.
protected int	pageSize

Constructor Summary

Constructors

Constructor	Description
PageManagerForFileChannel(FileChannel channel, long channelSize, int pageSize)

Method Summary

Modifier and Type	Method	Description
static PageManagerForFileChannel	create(FileChannel channel)
static PageManagerForFileChannel	create(FileChannel channel, int pageSize)
long	getEndPos()	The maximum position in the underlying buffer
int	getPageSize()	The pageSize.
org.aksw.commons.util.ref.Ref<Page>	getRefForPage(long page)
static ByteBuffer	map(FileChannel channel, FileChannel.MapMode mapMode, long start, long length)
org.aksw.commons.util.ref.Ref<Page>	requestBufferForPage(long page)

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.aksw.commons.io.block.api.PageManager

contentAtOrAfter, contentAtOrBefore, getSizeOfBlock, hasBlockAfter, hasBlockBefore, size

Field Details

DEFAULT_PAGE_SIZE

public static final int DEFAULT_PAGE_SIZE

See Also:

• Constant Field Values

pageCache

protected com.google.common.cache.Cache<Long,org.aksw.commons.util.ref.Ref<Page>> pageCache

The cache is crucial to the implementation. Setting its size to 0 will cause excessive allocation of pages and thus a timely OutOfMemory error.

channel

protected FileChannel channel

channelSize

protected long channelSize

We rely on the channel's size being constant. A growing size should work, a shrinking one will cause exceptions.

pageSize

protected int pageSize

Constructor Details

PageManagerForFileChannel

public PageManagerForFileChannel(FileChannel channel,
 long channelSize,
 int pageSize)

Method Details

create

public static PageManagerForFileChannel create(FileChannel channel)
                                        throws IOException

Throws:

IOException

create

public static PageManagerForFileChannel create(FileChannel channel,
 int pageSize)
                                        throws IOException

Throws:

IOException

getPageSize

public int getPageSize()

Description copied from interface: PageManager

The pageSize. Must never change during the life time of a page manager.

Specified by:

getPageSize in interface PageManager

Returns:

requestBufferForPage

public org.aksw.commons.util.ref.Ref<Page> requestBufferForPage(long page)

Specified by:

requestBufferForPage in interface PageManager

map

public static ByteBuffer map(FileChannel channel,
 FileChannel.MapMode mapMode,
 long start,
 long length)
                      throws IOException

Throws:

IOException

getRefForPage

public org.aksw.commons.util.ref.Ref<Page> getRefForPage(long page)
                                                  throws IOException

Throws:

IOException

getEndPos

public long getEndPos()

Description copied from interface: PageManager

The maximum position in the underlying buffer

Specified by:

getEndPos in interface PageManager

Returns: