Jackcess 5.2.0 · io.github.spannm.jackcess.impl.PageChannel

Field Summary

Modifier and Type	Field and Description
private final boolean	autoSync whether or not to force all writes to disk immediately
private final FileChannel	channel Channel containing the database
private final boolean	closeChannel whether or not the channel should be closed by this class
private CodecHandler	codecHandler handler for the current database encoding type
public static final ByteOrder	DEFAULT_BYTE_ORDER default byte order of access mdb files
private final ByteBuffer	forceBytes dummy buffer used when allocating new pages
private final JetFormat	format Format of the database in the channel
private TempPageHolder	fullPageEncodeBufferH temp page buffer used when pages cannot be partially encoded
private UsageMap	globalUsageMap Tracks free pages in the database.
private static final byte[]	INVALID_PAGE_BYTE_HEADER invalid page header, used when deallocating old pages.
pack-priv static final int	INVALID_PAGE_NUMBER
private final ByteBuffer	invalidPageBytes buffer used when deallocating old pages.
private long	knownFileSize Cached size of the channel, in bytes.
pack-priv static final int	PAGE_GLOBAL_USAGE_MAP Global usage map always lives on page 1
pack-priv static final int	ROW_GLOBAL_USAGE_MAP Global usage map always lives at row 0
private TempBufferHolder	tempDecodeBufferH
private int	writeCount

Constructor Summary

Access	Constructor and Description
protected	PageChannel(boolean testing) Only used by unit tests
public	PageChannel(FileChannel Channel containing the database channel, boolean closeChannel, JetFormat Format of the database in the channel format, boolean autoSync)

Method Summary

Modifier and Type	Method and Description
public int	allocateNewPage() Allocates a new page in the database.
private void	applyHeaderMask(ByteBuffer buffer) Applies the XOR mask to the database header in the given buffer.
private void	assertWriting() Asserts that a write operation is in progress.
public void	close() Implements java.nio.channels.Channel.close. Closes this channel.
public static ByteBuffer	Returns: A newly-allocated buffer of the given size and DEFAULT_BYTE_ORDER byte order createBuffer(int size) Returns a newly-allocated buffer of the given size and DEFAULT_BYTE_ORDER byte order.
public static ByteBuffer	Returns: A newly-allocated buffer of the given size and byte order createBuffer(int size, ByteOrder order) Returns a newly-allocated buffer of the given size and byte order.
public ByteBuffer	Returns: A newly-allocated buffer that can be passed to readPage createPageBuffer() Returns a newly-allocated buffer that can be passed to readPage.
public void	deallocatePage(int pageNumber) Deallocate a previously used page in the database.
public void	finishWrite() Completes a "logical" write operation.
public void	flush() Implements java.io.Flushable.flush. Flushes this stream by writing any buffered output to the underlying stream.
private long	getFileSize() Returns: the current channel size, in bytes, tracked locally instead of queried from the OS on every call
public JetFormat	getFormat()
private int	getNextPageNumber(long size) Returns the next page number based on the given file size.
private long	getPageOffset(int pageNumber) Returns the offset for a page within the file.
public void	initialize(DatabaseImpl database, CodecProvider codecProvider) Does second-stage initialization, must be called after construction.
public boolean	isAutoSync()
public boolean	isOpen() Implements java.nio.channels.Channel.isOpen. Tells whether or not this channel is open.
public boolean	isWriting() Returns `true` if a logical write operation is in progress, `false` otherwise.
public static ByteBuffer	Returns: a duplicate of the current buffer narrowed to the given position and limit. mark will be set at the current position. narrowBuffer(ByteBuffer buffer, int position, int limit) Returns a duplicate of the current buffer narrowed to the given position and limit.
public void	readPage(ByteBuffer Buffer to read the page into buffer, int Number of the page to read in (starting at 0) pageNumber) Reads the given page into the buffer, decoding it if necessary.
public void	readRootPage(ByteBuffer Buffer to read the root page into buffer) Reads the root page into the buffer; this works before the channel is fully initialized.
public void	startExclusiveWrite() Begins an exclusive "logical" write operation (throws an exception if another write operation is outstanding).
public void	startWrite() Begins a "logical" write operation.
private void	validatePageNumber(int pageNumber) Validates that the given pageNumber is valid for this database.
public static ByteBuffer	wrap(byte[] bytes) Returns a ByteBuffer wrapping the given bytes and configured with the default byte order.
public void	writePage(ByteBuffer Page to write page, int Page number to write the page to pageNumber) Write a page to disk
public void	writePage(ByteBuffer Page to write page, int Page number to write the page to pageNumber, int offset within the page at which to start writing the page data pageOffset) Write a page (or part of a page) to disk

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

autoSync	back to summary
private final boolean autoSync whether or not to force all writes to disk immediately

channel	back to summary
private final FileChannel channel Channel containing the database

closeChannel	back to summary
private final boolean closeChannel whether or not the channel should be closed by this class

codecHandler	back to summary
private CodecHandler codecHandler handler for the current database encoding type

DEFAULT_BYTE_ORDER	back to summary
public static final ByteOrder DEFAULT_BYTE_ORDER default byte order of access mdb files

forceBytes	back to summary
private final ByteBuffer forceBytes dummy buffer used when allocating new pages

format	back to summary
private final JetFormat format Format of the database in the channel

fullPageEncodeBufferH	back to summary
private TempPageHolder fullPageEncodeBufferH temp page buffer used when pages cannot be partially encoded

globalUsageMap	back to summary
private UsageMap globalUsageMap Tracks free pages in the database.

INVALID_PAGE_BYTE_HEADER	back to summary
private static final byte[] INVALID_PAGE_BYTE_HEADER invalid page header, used when deallocating old pages. data pages generally have 4 interesting bytes at the beginning which we want to reset.

INVALID_PAGE_NUMBER	back to summary
pack-priv static final int INVALID_PAGE_NUMBER

invalidPageBytes	back to summary
private final ByteBuffer invalidPageBytes buffer used when deallocating old pages. data pages generally have 4 interesting bytes at the beginning which we want to reset.

knownFileSize	back to summary
private long knownFileSize Cached size of the channel, in bytes. The file only ever grows, and only via `allocateNewPage`, so this is tracked locally to avoid an OS-level size query (e.g. `fstat`) on every single page read/write. Negative until lazily initialized.

PAGE_GLOBAL_USAGE_MAP	back to summary
pack-priv static final int PAGE_GLOBAL_USAGE_MAP Global usage map always lives on page 1

ROW_GLOBAL_USAGE_MAP	back to summary
pack-priv static final int ROW_GLOBAL_USAGE_MAP Global usage map always lives at row 0

tempDecodeBufferH	back to summary
private TempBufferHolder tempDecodeBufferH

writeCount	back to summary
private int writeCount

Constructor Detail

PageChannel	back to summary
protected PageChannel(boolean testing) Only used by unit tests

PageChannel	back to summary
public PageChannel(FileChannel channel, boolean closeChannel, JetFormat format, boolean autoSync) Parameters channel:FileChannel Channel containing the database format:JetFormat Format of the database in the channel

Method Detail

allocateNewPage	back to summary
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)`.

applyHeaderMask	back to summary
private void applyHeaderMask(ByteBuffer buffer) Applies the XOR mask to the database header in the given buffer.

assertWriting	back to summary
private void assertWriting() Asserts that a write operation is in progress.

close back to summary

close	back to summary
public void close() throws IOException Implements java.nio.channels.Channel.close. Doc from java.nio.channels.Channel.close. Closes this channel. After a channel is closed, any further attempt to invoke I/O operations upon it will cause a `ClosedChannelException` to be thrown. If this channel is already closed then invoking this method has no effect. This method may be invoked at any time. If some other thread has already invoked it, however, then another invocation will block until the first invocation is complete, after which it will return without effect. Annotations @Override Exceptions IOException: If an I/O error occurs

public void close() throws IOException

Implements java.nio.channels.Channel.close.

Doc from java.nio.channels.Channel.close.

Closes this channel.

After a channel is closed, any further attempt to invoke I/O operations upon it will cause a ClosedChannelException to be thrown.

If this channel is already closed then invoking this method has no effect.

This method may be invoked at any time. If some other thread has already invoked it, however, then another invocation will block until the first invocation is complete, after which it will return without effect.

Annotations

@Override

Exceptions

IOException:: If an I/O error occurs

createBuffer	back to summary
public static ByteBuffer createBuffer(int size) Returns a newly-allocated buffer of the given size and DEFAULT_BYTE_ORDER byte order. Returns:ByteBuffer A newly-allocated buffer of the given size and DEFAULT_BYTE_ORDER byte order

createBuffer

back to summary

public static ByteBuffer createBuffer(int size)

Returns a newly-allocated buffer of the given size and DEFAULT_BYTE_ORDER byte order.

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

createBuffer	back to summary
public static ByteBuffer createBuffer(int size, ByteOrder order) Returns a newly-allocated buffer of the given size and byte order. Returns:ByteBuffer A newly-allocated buffer of the given size and byte order

createBuffer

back to summary

public static ByteBuffer createBuffer(int size, ByteOrder order)

Returns a newly-allocated buffer of the given size and byte order.

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

createPageBuffer	back to summary
public ByteBuffer createPageBuffer() Returns a newly-allocated buffer that can be passed to readPage. Returns:ByteBuffer A newly-allocated buffer that can be passed to readPage

createPageBuffer

back to summary

public ByteBuffer createPageBuffer()

Returns a newly-allocated buffer that can be passed to readPage.

Returns:ByteBuffer: A newly-allocated buffer that can be passed to readPage

deallocatePage	back to summary
public void deallocatePage(int pageNumber) throws IOException Deallocate a previously used page in the database.

finishWrite	back to summary
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,

flush	back to summary
public void flush() throws IOException Implements java.io.Flushable.flush. Doc from java.io.Flushable.flush. Flushes this stream by writing any buffered output to the underlying stream. Annotations @Override Exceptions IOException: If an I/O error occurs

flush

back to summary

public void flush() throws IOException

Implements java.io.Flushable.flush.

Doc from java.io.Flushable.flush.

Flushes this stream by writing any buffered output to the underlying stream.

Annotations

@Override

Exceptions

IOException:: If an I/O error occurs

getFileSize	back to summary
private long getFileSize() throws IOException Returns:long the current channel size, in bytes, tracked locally instead of queried from the OS on every call

getFormat	back to summary
public JetFormat getFormat()

getNextPageNumber	back to summary
private int getNextPageNumber(long size) Returns the next page number based on the given file size.

getPageOffset	back to summary
private long getPageOffset(int pageNumber) Returns the offset for a page within the file.

initialize	back to summary
public void initialize(DatabaseImpl database, CodecProvider codecProvider) throws IOException Does second-stage initialization, must be called after construction.

isAutoSync	back to summary
public boolean isAutoSync()

isOpen	back to summary
public boolean isOpen() Implements java.nio.channels.Channel.isOpen. Doc from java.nio.channels.Channel.isOpen. Tells whether or not this channel is open. Annotations @Override

isOpen

back to summary

public boolean isOpen()

Implements java.nio.channels.Channel.isOpen.

Doc from java.nio.channels.Channel.isOpen.

Tells whether or not this channel is open.

Annotations

@Override

isWriting	back to summary
public boolean isWriting() Returns `true` if a logical write operation is in progress, `false` otherwise.

narrowBuffer	back to summary
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. Returns:ByteBuffer a duplicate of the current buffer narrowed to the given position and limit. mark will be set at the current position.

narrowBuffer

back to summary

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.

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

readPage	back to summary
public void readPage(ByteBuffer buffer, int pageNumber) throws IOException Reads the given page into the buffer, decoding it if necessary. Parameters buffer:ByteBuffer Buffer to read the page into pageNumber:int Number of the page to read in (starting at 0)

readPage

back to summary

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

Reads the given page into the buffer, decoding it if necessary.

Parameters

buffer:ByteBuffer: Buffer to read the page into
pageNumber:int: Number of the page to read in (starting at 0)

readRootPage	back to summary
public void readRootPage(ByteBuffer buffer) throws IOException Reads the root page into the buffer; this works before the channel is fully initialized. Parameters buffer:ByteBuffer Buffer to read the root page into

readRootPage

back to summary

public void readRootPage(ByteBuffer buffer) throws IOException

Reads the root page into the buffer; this works before the channel is fully initialized.

Parameters

buffer:ByteBuffer: Buffer to read the root page into

startExclusiveWrite	back to summary
public void startExclusiveWrite() Begins an exclusive "logical" write operation (throws an exception if another write operation is outstanding). See `finishWrite` for more details.

startWrite	back to summary
public void startWrite() Begins a "logical" write operation. See `finishWrite` for more details.

validatePageNumber	back to summary
private void validatePageNumber(int pageNumber) throws IOException Validates that the given pageNumber is valid for this database.

wrap	back to summary
public static ByteBuffer wrap(byte[] bytes) Returns a ByteBuffer wrapping the given bytes and configured with the default byte order.

writePage	back to summary
public void writePage(ByteBuffer page, int pageNumber) throws IOException Write a page to disk Parameters page:ByteBuffer Page to write pageNumber:int Page number to write the page to

writePage

back to summary

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

Write a page to disk

Parameters

page:ByteBuffer: Page to write
pageNumber:int: Page number to write the page to

writePage	back to summary
public void writePage(ByteBuffer page, int pageNumber, int pageOffset) throws IOException Write a page (or part of a page) to disk Parameters page:ByteBuffer Page to write pageNumber:int Page number to write the page to pageOffset:int offset within the page at which to start writing the page data

writePage

back to summary

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

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

Parameters

page:ByteBuffer: Page to write
pageNumber:int: Page number to write the page to
pageOffset:int: offset within the page at which to start writing the page data

public Class PageChannel

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail