org.tmatesoft.sqljet.core.internal.fs

Class SqlJetMemJournal

java.lang.Object

org.tmatesoft.sqljet.core.internal.fs.SqlJetMemJournal

All Implemented Interfaces:

ISqlJetFile

public class SqlJetMemJournal
extends java.lang.Object
implements ISqlJetFile

This subclass is a subclass of sqlite3_file. Each open memory-journal is an instance of this class.

Field Summary

Fields inherited from interface org.tmatesoft.sqljet.core.internal.ISqlJetFile

PENDING_BYTE, RESERVED_BYTE, SHARED_FIRST, SHARED_SIZE

Constructor Summary

Constructors

Constructor and Description
SqlJetMemJournal()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	checkReservedLock() This routine checks if there is a RESERVED lock held on the specified file by this or any other process.
void	close() Close a file.
java.util.Set<SqlJetDeviceCharacteristics>	deviceCharacteristics() Return the device characteristics for the file.
long	fileSize() Determine the current size of a file in bytes
SqlJetFileType	getFileType() Returns file type.
SqlJetLockType	getLockType() Returns lock type of file.
java.util.Set<SqlJetFileOpenPermission>	getPermissions() Returns assiciated permissions.
boolean	isMemJournal() Return true if the file-handle passed as an argument is an in-memory journal
boolean	lock(SqlJetLockType lockType) Lock the file with the lock specified by parameter locktype - one of the following: (1) SHARED (2) RESERVED (3) PENDING (4) EXCLUSIVE Sometimes when requesting one lock state, additional lock states are inserted in between.
int	read(ISqlJetMemoryPointer buffer, int amount, long offset) Read data from a file into a buffer.
int	sectorSize() Return the sector size in bytes of the underlying block device for the specified file.
void	sync(java.util.Set<SqlJetSyncFlags> syncFlags) Make sure all writes to a particular file are committed to disk.
void	truncate(long size) Truncate an open file to a specified size
boolean	unlock(SqlJetLockType lockType) Lower the locking level on file descriptor pFile to locktype.
void	write(ISqlJetMemoryPointer buffer, int amount, long offset) Write data from a buffer into a file.

Methods inherited from class java.lang.Object

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

Constructor Detail

SqlJetMemJournal

public SqlJetMemJournal()

Method Detail

isMemJournal

public boolean isMemJournal()

Description copied from interface: ISqlJetFile

Return true if the file-handle passed as an argument is an in-memory journal

Specified by:

isMemJournal in interface ISqlJetFile

read

public int read(ISqlJetMemoryPointer buffer,
       int amount,
       long offset)

Description copied from interface: ISqlJetFile

Read data from a file into a buffer.

Specified by:

read in interface ISqlJetFile

Returns:

write

public void write(ISqlJetMemoryPointer buffer,
         int amount,
         long offset)

Description copied from interface: ISqlJetFile

Write data from a buffer into a file.

Specified by:

write in interface ISqlJetFile

truncate

public void truncate(long size)

Description copied from interface: ISqlJetFile

Truncate an open file to a specified size

Specified by:

truncate in interface ISqlJetFile

close

public void close()

Description copied from interface: ISqlJetFile

Close a file.

Specified by:

close in interface ISqlJetFile

sync

public void sync(java.util.Set<SqlJetSyncFlags> syncFlags)

Description copied from interface: ISqlJetFile

Make sure all writes to a particular file are committed to disk. If dataOnly==false then both the file itself and its metadata (file size, access time, etc) are synced. If dataOnly==true then only the file data is synced. Also make sure that the directory entry for the file has been created by fsync-ing the directory that contains the file. If we do not do this and we encounter a power failure, the directory entry for the journal might not exist after we reboot. The next SqlJet to access the file will not know that the journal exists (because the directory entry for the journal was never created) and the transaction will not roll back - possibly leading to database corruption.

Specified by:

sync in interface ISqlJetFile

fileSize

public long fileSize()

Description copied from interface: ISqlJetFile

Determine the current size of a file in bytes

Specified by:

fileSize in interface ISqlJetFile

Returns:

checkReservedLock

public boolean checkReservedLock()

Description copied from interface: ISqlJetFile

This routine checks if there is a RESERVED lock held on the specified file by this or any other process. The return value is set unless an I/O error occurs during lock checking.

Specified by:

checkReservedLock in interface ISqlJetFile

Returns:

deviceCharacteristics

public java.util.Set<SqlJetDeviceCharacteristics> deviceCharacteristics()

Description copied from interface: ISqlJetFile

Return the device characteristics for the file.

Specified by:

deviceCharacteristics in interface ISqlJetFile

Returns:

getFileType

public SqlJetFileType getFileType()

Description copied from interface: ISqlJetFile

Returns file type.

Specified by:

getFileType in interface ISqlJetFile

Returns:

SqlJetFileType

getLockType

public SqlJetLockType getLockType()

Description copied from interface: ISqlJetFile

Returns lock type of file.

Specified by:

getLockType in interface ISqlJetFile

Returns:

getPermissions

public java.util.Set<SqlJetFileOpenPermission> getPermissions()

Description copied from interface: ISqlJetFile

Returns assiciated permissions.

Specified by:

getPermissions in interface ISqlJetFile

Returns:

SqlJetFileOpenPermission

lock

public boolean lock(SqlJetLockType lockType)

Description copied from interface: ISqlJetFile

Lock the file with the lock specified by parameter locktype - one of the following: (1) SHARED (2) RESERVED (3) PENDING (4) EXCLUSIVE Sometimes when requesting one lock state, additional lock states are inserted in between. The locking might fail on one of the later transitions leaving the lock state different from what it started but still short of its goal. The following chart shows the allowed transitions and the inserted intermediate states: UNLOCKED -> SHARED SHARED -> RESERVED SHARED -> (PENDING) -> EXCLUSIVE RESERVED -> (PENDING) -> EXCLUSIVE PENDING -> EXCLUSIVE This routine will only increase a lock.

Specified by:

lock in interface ISqlJetFile

Returns:

sectorSize

public int sectorSize()

Description copied from interface: ISqlJetFile

Return the sector size in bytes of the underlying block device for the specified file. This is almost always 512 bytes, but may be larger for some devices. SqlJet code assumes this function cannot fail. It also assumes that if two files are created in the same file-system directory (i.e. a database and its journal file) that the sector size will be the same for both.

Specified by:

sectorSize in interface ISqlJetFile

Returns:

unlock

public boolean unlock(SqlJetLockType lockType)

Description copied from interface: ISqlJetFile

Lower the locking level on file descriptor pFile to locktype. locktype must be either NONE or SHARED. If the locking level of the file descriptor is already at or below the requested locking level, this routine is a no-op.

Specified by:

unlock in interface ISqlJetFile

Returns: