LogBufferElement (Apache Derby V10.14 Internals)

java.lang.Object
- org.apache.derby.impl.store.replication.buffer.LogBufferElement

```
class LogBufferElement
extends java.lang.Object
```
ReplicationLogBuffer consists of n LogBufferElements, each of which can store a number of log records in a single byte[].
The format of each log record in the LogBufferElement is the same as is written to log file in LogAccessFile:
(int) total_length (data[].length + optionaldata[].length)
(long) instant
(byte[]) data+optionaldata
(int) total_length

In addition to adding a chunk of log records to the byte[], the greatestInstant variable is updated for every append so that getLastInstant can be used to get the highest log instant in this LogBufferElement.

Field Summary

Fields
Modifier and Type Field Description

private byte[] bufferdata

private long greatestInstant

private int position

private boolean recycleMe

Fields
Modifier and Type	Field	Description
`private byte[]`	`bufferdata`
`private long`	`greatestInstant`
`private int`	`position`
`private boolean`	`recycleMe`

Constructor Summary

Constructors
Modifier Constructor Description

protected LogBufferElement(int bufferSize)

Constructors
Modifier	Constructor	Description
`protected`	`LogBufferElement(int bufferSize)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`private int`	`appendBytes(byte[] b, int offset, int pos, int length)`	Append a byte[] to this LogBufferElement.
`protected void`	`appendLog(long greatestInstant, byte[] log, int logOffset, int logLength)`	Append a chunk of log records to this LogBufferElement.
`protected int`	`freeSize()`
`protected byte[]`	`getData()`
`protected long`	`getLastInstant()`
`protected void`	`init()`	Resets all variables to default values.
`protected boolean`	`isRecyclable()`
`protected void`	`setRecyclable(boolean r)`
`protected int`	`size()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - bufferdata
```
private final byte[] bufferdata
```
  - position
```
private int position
```
  - greatestInstant
```
private long greatestInstant
```
  - recycleMe
```
private boolean recycleMe
```
- Constructor Detail
  - LogBufferElement
```
protected LogBufferElement(int bufferSize)
```
- Method Detail
  - init
```
protected void init()
```
    Resets all variables to default values. Should be called before a LogBufferElement is reused.
  - appendLog
```
protected void appendLog(long greatestInstant,
                         byte[] log,
                         int logOffset,
                         int logLength)
```
    Append a chunk of log records to this LogBufferElement.
    
    Parameters:
    
    greatestInstant - the instant of the log record that was added last to this chunk of log
    
    log - the chunk of log records
    
    logOffset - offset in log to start copy from
    
    logLength - number of bytes to copy, starting from logOffset
  - getData
```
protected byte[] getData()
```
    Returns:
    
    A byte[] representation of the log records appended to this LogBufferElement
  - getLastInstant
```
protected long getLastInstant()
```
    Returns:
    
    The highest log instant appended to this LogBufferElement
  - freeSize
```
protected int freeSize()
```
    Returns:
    
    Number of unused bytes in this LogBufferElement
  - size
```
protected int size()
```
    Returns:
    
    Number of used bytes in this LogBufferElement
  - isRecyclable
```
protected boolean isRecyclable()
```
    Returns:
    
    true if this LogBufferElement should be reused, i.e. added to freeBuffers after being consumed.
  - setRecyclable
```
protected void setRecyclable(boolean r)
```
  - appendBytes
```
private int appendBytes(byte[] b,
                        int offset,
                        int pos,
                        int length)
```
    Append a byte[] to this LogBufferElement.
    
    Parameters:
    
    b - where the bytes are copied from
    
    offset - offset in b to start copying from
    
    pos - the position in this LogBufferElement to start copying to
    
    length - number of bytes to copy from b, starting from offset
    
    Returns:
    
    new position

Class LogBufferElement

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

bufferdata

position

greatestInstant

recycleMe

Constructor Detail

LogBufferElement

Method Detail

init

appendLog

getData

getLastInstant

freeSize

size

isRecyclable

setRecyclable

appendBytes