com.sleepycat.je.log

Class LogBuffer

java.lang.Object

com.sleepycat.je.log.LogBuffer

All Implemented Interfaces:

LogSource

public class LogBuffer
extends java.lang.Object
implements LogSource

LogBuffers hold outgoing, newly written log entries.

Constructor Summary

Constructors

Constructor and Description
LogBuffer(java.nio.ByteBuffer buffer, long firstLsn)
LogBuffer(int capacity, EnvironmentImpl env)

Method Summary

Methods

Modifier and Type	Method and Description
(package private) boolean	containsLsn(long lsn) Support for reading out of a still-in-memory log.
java.nio.ByteBuffer	getBytes(long fileOffset) Fill the destination byte array with bytes.
java.nio.ByteBuffer	getBytes(long fileOffset, int numBytes) Fill the destination byte array with the requested number of bytes.
(package private) int	getCapacity()
java.nio.ByteBuffer	getDataBuffer()
long	getFirstLsn() Return first LSN held in this buffer.
int	getLogVersion() Entries in write buffers are always the current version.
(package private) boolean	getRewriteAllowed()
(package private) boolean	hasRoom(int numBytes) Check capacity of buffer.
void	latchForWrite() When modifying the buffer, acquire the readLatch.
(package private) void	registerLsn(long lsn) This LSN has been written to the log.
(package private) void	reinit()
void	release() We're done with this log source.
(package private) void	setRewriteAllowed()

Methods inherited from class java.lang.Object

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

Constructor Detail

LogBuffer

LogBuffer(int capacity,
         EnvironmentImpl env)
    throws DatabaseException

Throws:

DatabaseException

LogBuffer

LogBuffer(java.nio.ByteBuffer buffer,
         long firstLsn)

Method Detail

reinit

void reinit()
      throws DatabaseException

Throws:

DatabaseException

getFirstLsn

public long getFirstLsn()

Return first LSN held in this buffer. Assumes the log write latch is held.

registerLsn

void registerLsn(long lsn)
           throws DatabaseException

This LSN has been written to the log.

Throws:

DatabaseException

hasRoom

boolean hasRoom(int numBytes)

Check capacity of buffer. Assumes that the log write latch is held.

Returns:

true if this buffer can hold this many more bytes.

getDataBuffer

public java.nio.ByteBuffer getDataBuffer()

Returns:

the actual data buffer.

getCapacity

int getCapacity()

Returns:

capacity in bytes

containsLsn

boolean containsLsn(long lsn)

Support for reading out of a still-in-memory log. Can be used to determine if a log entry with a given LSN is contained in this buffer, or whether an arbitrary LSN location is present in the buffer.

Returns:

true if this buffer holds the data at this LSN location. If true is returned, the buffer will be latched for read. Returns false if LSN is not here, and releases the read latch.

latchForWrite

public void latchForWrite()
                   throws DatabaseException

When modifying the buffer, acquire the readLatch. Call release() to release the latch. Note that containsLsn() acquires the latch for reading.

Throws:

DatabaseException

release

public void release()

Description copied from interface: LogSource

We're done with this log source.

Specified by:

release in interface LogSource

See Also:

LogSource.release()

getRewriteAllowed

boolean getRewriteAllowed()

setRewriteAllowed

void setRewriteAllowed()

getBytes

public java.nio.ByteBuffer getBytes(long fileOffset)

Description copied from interface: LogSource

Fill the destination byte array with bytes. The offset indicates the absolute log file position.

Specified by:

getBytes in interface LogSource

See Also:

LogSource.getBytes(long)

getBytes

public java.nio.ByteBuffer getBytes(long fileOffset,
                           int numBytes)
                             throws ChecksumException

Description copied from interface: LogSource

Fill the destination byte array with the requested number of bytes. The offset indicates the absolute position in the log file.

Specified by:

getBytes in interface LogSource

Throws:

ChecksumException

See Also:

LogSource.getBytes(long)

getLogVersion

public int getLogVersion()

Entries in write buffers are always the current version.

Specified by:

getLogVersion in interface LogSource