H2 Database Engine 2.3.232 · org.h2.store.fs.niomapped.FileNioMapped

Modifier and Type	Field and Description
private FileChannel	channel
private long	fileLength
private static final int	GC_TIMEOUT_MS
private MappedByteBuffer	mapped
private final FileChannel.MapMode	mode
private final String	name

Access	Constructor and Description
pack-priv	FileNioMapped(String fileName, String mode)

Method Summary

Modifier and Type	Method and Description
private static void	checkFileSizeLimit(long length)
public void	force(boolean If `true` then this method is required to force changes to both the file's content and metadata to be written to storage; otherwise, it need only force content changes to be written metaData) Overrides org.h2.store.fs.FileBase.force. Forces any updates to this channel's file to be written to the storage device that contains it.
public void	implCloseChannel() Overrides org.h2.store.fs.FileBase.implCloseChannel. Closes this channel.
protected void	implTruncate(long the new size newLength) Implements abstract org.h2.store.fs.FileBaseDefault.implTruncate. The truncate implementation.
public synchronized int	read(ByteBuffer The buffer into which bytes are to be transferred dst, long The file position at which the transfer is to begin; must be non-negative pos) Overrides org.h2.store.fs.FileBase.read. Reads a sequence of bytes from this channel into the given buffer, starting at the given file position.
private void	reMap() Re-map byte buffer into memory, called when file size has changed or file was created.
public synchronized void	setFileLength(long newLength)
public synchronized long	size() Implements abstract java.nio.channels.FileChannel.size. Implements java.nio.channels.SeekableByteChannel.size. Returns the current size of this channel's file.
public String	toString() Overrides java.lang.Object.toString. Returns a string representation of the object.
public synchronized FileLock	tryLock(long The position at which the locked region is to start; must be non-negative position, long The size of the locked region; must be non-negative, and the sum `position` + `size` must be non-negative. A value of zero means to lock all bytes from the specified starting position to the end of the file, regardless of whether the file is subsequently extended or truncated size, boolean `true` to request a shared lock, `false` to request an exclusive lock shared) Overrides org.h2.store.fs.FileBase.tryLock. Attempts to acquire a lock on the given region of this channel's file.
private void	unMap()
public synchronized int	write(ByteBuffer The buffer from which bytes are to be transferred src, long The file position at which the transfer is to begin; must be non-negative position) Overrides org.h2.store.fs.FileBase.write. Writes a sequence of bytes to this channel from the given buffer, starting at the given file position.

Inherited from org.h2.store.fs.FileBaseDefault:: position position read truncate write

channel	back to summary
private FileChannel channel

fileLength	back to summary
private long fileLength

GC_TIMEOUT_MS	back to summary
private static final int GC_TIMEOUT_MS

mapped	back to summary
private MappedByteBuffer mapped

mode	back to summary
private final FileChannel.MapMode mode

name	back to summary
private final String name

FileNioMapped	back to summary
pack-priv FileNioMapped(String fileName, String mode) throws IOException

Method Detail

checkFileSizeLimit	back to summary
private static void checkFileSizeLimit(long length) throws IOException

force back to summary

force	back to summary
public void force(boolean metaData) throws IOException Overrides org.h2.store.fs.FileBase.force. Doc from java.nio.channels.FileChannel.force. Forces any updates to this channel's file to be written to the storage device that contains it. If this channel's file resides on a local storage device then when this method returns it is guaranteed that all changes made to the file since this channel was created, or since this method was last invoked, will have been written to that device. This is useful for ensuring that critical information is not lost in the event of a system crash. If the file does not reside on a local device then no such guarantee is made. The `metaData` parameter can be used to limit the number of I/O operations that this method is required to perform. Passing `false` for this parameter indicates that only updates to the file's content need be written to storage; passing `true` indicates that updates to both the file's content and metadata must be written, which generally requires at least one more I/O operation. Whether this parameter actually has any effect is dependent upon the underlying operating system and is therefore unspecified. Invoking this method may cause an I/O operation to occur even if the channel was only opened for reading. Some operating systems, for example, maintain a last-access time as part of a file's metadata, and this time is updated whenever the file is read. Whether or not this is actually done is system-dependent and is therefore unspecified. This method is only guaranteed to force changes that were made to this channel's file via the methods defined in this class, or the methods defined by `java.io.FileOutputStream` or `java.io.RandomAccessFile` when the channel was obtained with the `getChannel` method. It may or may not force changes that were made by modifying the content of a `mapped byte buffer` obtained by invoking the `map` method. Invoking the `force` method of the mapped byte buffer will force changes made to the buffer's content to be written. Parameters metaData:boolean If `true` then this method is required to force changes to both the file's content and metadata to be written to storage; otherwise, it need only force content changes to be written Annotations @Override Exceptions IOException: If some other I/O error occurs

public void force(boolean metaData) throws IOException

Overrides org.h2.store.fs.FileBase.force.

Doc from java.nio.channels.FileChannel.force.

Forces any updates to this channel's file to be written to the storage device that contains it.

If this channel's file resides on a local storage device then when this method returns it is guaranteed that all changes made to the file since this channel was created, or since this method was last invoked, will have been written to that device. This is useful for ensuring that critical information is not lost in the event of a system crash.

If the file does not reside on a local device then no such guarantee is made.

The metaData parameter can be used to limit the number of I/O operations that this method is required to perform. Passing false for this parameter indicates that only updates to the file's content need be written to storage; passing true indicates that updates to both the file's content and metadata must be written, which generally requires at least one more I/O operation. Whether this parameter actually has any effect is dependent upon the underlying operating system and is therefore unspecified.

Invoking this method may cause an I/O operation to occur even if the channel was only opened for reading. Some operating systems, for example, maintain a last-access time as part of a file's metadata, and this time is updated whenever the file is read. Whether or not this is actually done is system-dependent and is therefore unspecified.

This method is only guaranteed to force changes that were made to this channel's file via the methods defined in this class, or the methods defined by java.io.FileOutputStream or java.io.RandomAccessFile when the channel was obtained with the getChannel method. It may or may not force changes that were made by modifying the content of a mapped byte buffer obtained by invoking the map method. Invoking the force method of the mapped byte buffer will force changes made to the buffer's content to be written.

Parameters

metaData:boolean: If true then this method is required to force changes to both the file's content and metadata to be written to storage; otherwise, it need only force content changes to be written

Annotations

@Override

Exceptions

IOException:: If some other I/O error occurs

implCloseChannel back to summary

implCloseChannel	back to summary
public void implCloseChannel() throws IOException Overrides org.h2.store.fs.FileBase.implCloseChannel. Doc from java.nio.channels.spi.AbstractInterruptibleChannel.implCloseChannel. Closes this channel. This method is invoked by the `close` method in order to perform the actual work of closing the channel. This method is only invoked if the channel has not yet been closed, and it is never invoked more than once. An implementation of this method must arrange for any other thread that is blocked in an I/O operation upon this channel to return immediately, either by throwing an exception or by returning normally. Annotations @Override Exceptions IOException: If an I/O error occurs while closing the channel

public void implCloseChannel() throws IOException

Overrides org.h2.store.fs.FileBase.implCloseChannel.

Doc from java.nio.channels.spi.AbstractInterruptibleChannel.implCloseChannel.

Closes this channel.

This method is invoked by the close method in order to perform the actual work of closing the channel. This method is only invoked if the channel has not yet been closed, and it is never invoked more than once.

An implementation of this method must arrange for any other thread that is blocked in an I/O operation upon this channel to return immediately, either by throwing an exception or by returning normally.

Annotations

@Override

Exceptions

IOException:: If an I/O error occurs while closing the channel

implTruncate	back to summary
protected void implTruncate(long newLength) throws IOException Implements abstract org.h2.store.fs.FileBaseDefault.implTruncate. Doc from org.h2.store.fs.FileBaseDefault.implTruncate. The truncate implementation. Parameters newLength:long the new size Annotations @Override Exceptions IOException: on failure

implTruncate

back to summary

protected void implTruncate(long newLength) throws IOException

Implements abstract org.h2.store.fs.FileBaseDefault.implTruncate.

Doc from org.h2.store.fs.FileBaseDefault.implTruncate.

The truncate implementation.

Parameters

newLength:long: the new size

Annotations

@Override

Exceptions

IOException:: on failure

read back to summary

read	back to summary
public synchronized int read(ByteBuffer dst, long pos) throws IOException Overrides org.h2.store.fs.FileBase.read. Doc from java.nio.channels.FileChannel.read. Reads a sequence of bytes from this channel into the given buffer, starting at the given file position. This method works in the same manner as the `read(ByteBuffer)` method, except that bytes are read starting at the given file position rather than at the channel's current position. This method does not modify this channel's position. If the given position is greater than or equal to the file's current size then no bytes are read. Parameters dst:ByteBuffer The buffer into which bytes are to be transferred pos:long The file position at which the transfer is to begin; must be non-negative Returns:int The number of bytes read, possibly zero, or `-1` if the given position is greater than or equal to the file's current size Annotations @Override Exceptions IOException: If some other I/O error occurs

public synchronized int read(ByteBuffer dst, long pos) throws IOException

Overrides org.h2.store.fs.FileBase.read.

Doc from java.nio.channels.FileChannel.read.

Reads a sequence of bytes from this channel into the given buffer, starting at the given file position.

This method works in the same manner as the read(ByteBuffer) method, except that bytes are read starting at the given file position rather than at the channel's current position. This method does not modify this channel's position. If the given position is greater than or equal to the file's current size then no bytes are read.

Parameters

dst:ByteBuffer: The buffer into which bytes are to be transferred
pos:long: The file position at which the transfer is to begin; must be non-negative

Returns:int

The number of bytes read, possibly zero, or -1 if the given position is greater than or equal to the file's current size

Annotations

@Override

Exceptions

IOException:: If some other I/O error occurs

reMap	back to summary
private void reMap() throws IOException Re-map byte buffer into memory, called when file size has changed or file was created.

setFileLength	back to summary
public synchronized void setFileLength(long newLength) throws IOException

size	back to summary
public synchronized long size() throws IOException Implements abstract java.nio.channels.FileChannel.size. Implements java.nio.channels.SeekableByteChannel.size. Doc from java.nio.channels.FileChannel.size. Returns the current size of this channel's file. Returns:long The current size of this channel's file, measured in bytes Annotations @Override Exceptions IOException: If some other I/O error occurs

size

back to summary

public synchronized long size() throws IOException

Implements abstract java.nio.channels.FileChannel.size.

Implements java.nio.channels.SeekableByteChannel.size.

Doc from java.nio.channels.FileChannel.size.

Returns the current size of this channel's file.

Returns:long

The current size of this channel's file, measured in bytes

Annotations

@Override

Exceptions

IOException:: If some other I/O error occurs

toString back to summary

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Doc from java.lang.Object.toString. Returns a string representation of the object. Satisfying this method's contract implies a non-`null` result must be returned. Returns:String a string representation of the object Annotations @Override

public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object. Satisfying this method's contract implies a non-null result must be returned.

Returns:String

a string representation of the object

Annotations

@Override

tryLock back to summary

tryLock	back to summary
public synchronized FileLock tryLock(long position, long size, boolean shared) throws IOException Overrides org.h2.store.fs.FileBase.tryLock. Doc from java.nio.channels.FileChannel.tryLock. Attempts to acquire a lock on the given region of this channel's file. This method does not block. An invocation always returns immediately, either having acquired a lock on the requested region or having failed to do so. If it fails to acquire a lock because an overlapping lock is held by another program then it returns `null`. If it fails to acquire a lock for any other reason then an appropriate exception is thrown. The region specified by the `position` and `size` parameters need not be contained within, or even overlap, the actual underlying file. Lock regions are fixed in size; if a locked region initially contains the end of the file and the file grows beyond the region then the new portion of the file will not be covered by the lock. If a file is expected to grow in size and a lock on the entire file is required then a region starting at zero, and no smaller than the expected maximum size of the file, should be locked. The zero-argument `tryLock()` method simply locks a region of size `Long#MAX_VALUE`. If the `position` is non-negative and the `size` is zero, then a lock of size `Long.MAX_VALUE - position` is returned. Some operating systems do not support shared locks, in which case a request for a shared lock is automatically converted into a request for an exclusive lock. Whether the newly-acquired lock is shared or exclusive may be tested by invoking the resulting lock object's `isShared` method. File locks are held on behalf of the entire Java virtual machine. They are not suitable for controlling access to a file by multiple threads within the same virtual machine. Parameters position:long The position at which the locked region is to start; must be non-negative size:long The size of the locked region; must be non-negative, and the sum `position` + `size` must be non-negative. A value of zero means to lock all bytes from the specified starting position to the end of the file, regardless of whether the file is subsequently extended or truncated shared:boolean `true` to request a shared lock, `false` to request an exclusive lock Returns:FileLock A lock object representing the newly-acquired lock, or `null` if the lock could not be acquired because another program holds an overlapping lock Annotations @Override Exceptions IOException: If some other I/O error occurs

public synchronized FileLock tryLock(long position, long size, boolean shared) throws IOException

Overrides org.h2.store.fs.FileBase.tryLock.

Doc from java.nio.channels.FileChannel.tryLock.

Attempts to acquire a lock on the given region of this channel's file.

This method does not block. An invocation always returns immediately, either having acquired a lock on the requested region or having failed to do so. If it fails to acquire a lock because an overlapping lock is held by another program then it returns null. If it fails to acquire a lock for any other reason then an appropriate exception is thrown.

The region specified by the position and size parameters need not be contained within, or even overlap, the actual underlying file. Lock regions are fixed in size; if a locked region initially contains the end of the file and the file grows beyond the region then the new portion of the file will not be covered by the lock. If a file is expected to grow in size and a lock on the entire file is required then a region starting at zero, and no smaller than the expected maximum size of the file, should be locked. The zero-argument tryLock() method simply locks a region of size Long#MAX_VALUE. If the position is non-negative and the size is zero, then a lock of size Long.MAX_VALUE - position is returned.

Some operating systems do not support shared locks, in which case a request for a shared lock is automatically converted into a request for an exclusive lock. Whether the newly-acquired lock is shared or exclusive may be tested by invoking the resulting lock object's isShared method.

File locks are held on behalf of the entire Java virtual machine. They are not suitable for controlling access to a file by multiple threads within the same virtual machine.

Parameters

position:long: The position at which the locked region is to start; must be non-negative
size:long: The size of the locked region; must be non-negative, and the sum position + size must be non-negative. A value of zero means to lock all bytes from the specified starting position to the end of the file, regardless of whether the file is subsequently extended or truncated
shared:boolean: true to request a shared lock, false to request an exclusive lock

Returns:FileLock

A lock object representing the newly-acquired lock, or null if the lock could not be acquired because another program holds an overlapping lock

Annotations

@Override

Exceptions

IOException:: If some other I/O error occurs

unMap	back to summary
private void unMap() throws IOException

write back to summary

write	back to summary
public synchronized int write(ByteBuffer src, long position) throws IOException Overrides org.h2.store.fs.FileBase.write. Doc from java.nio.channels.FileChannel.write. Writes a sequence of bytes to this channel from the given buffer, starting at the given file position. This method works in the same manner as the `write(ByteBuffer)` method, except that bytes are written starting at the given file position rather than at the channel's current position. This method does not modify this channel's position. If the given position is greater than or equal to the file's current size then the file will be grown to accommodate the new bytes; the values of any bytes between the previous end-of-file and the newly-written bytes are unspecified. If the file is open in append mode, then the effect of invoking this method is unspecified. Parameters src:ByteBuffer The buffer from which bytes are to be transferred position:long The file position at which the transfer is to begin; must be non-negative Returns:int The number of bytes written, possibly zero Annotations @Override Exceptions IOException: If some other I/O error occurs

public synchronized int write(ByteBuffer src, long position) throws IOException

Overrides org.h2.store.fs.FileBase.write.

Doc from java.nio.channels.FileChannel.write.

Writes a sequence of bytes to this channel from the given buffer, starting at the given file position.

This method works in the same manner as the write(ByteBuffer) method, except that bytes are written starting at the given file position rather than at the channel's current position. This method does not modify this channel's position. If the given position is greater than or equal to the file's current size then the file will be grown to accommodate the new bytes; the values of any bytes between the previous end-of-file and the newly-written bytes are unspecified.

If the file is open in append mode, then the effect of invoking this method is unspecified.

Parameters

src:ByteBuffer: The buffer from which bytes are to be transferred
position:long: The file position at which the transfer is to begin; must be non-negative

Returns:int

The number of bytes written, possibly zero

Annotations

@Override

Exceptions

IOException:: If some other I/O error occurs

pack-priv Class FileNioMapped

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