LogEntryHeader (starrocks-bdb-je 18.3.17 API)

java.lang.Object
- com.sleepycat.je.log.LogEntryHeader

```
public class LogEntryHeader
extends Object
```
A LogEntryHeader embodies the header information at the beginning of each log entry file.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`CHECKSUM_BYTES`
`static int`	`ENTRYTYPE_OFFSET`
`static int`	`MAX_HEADER_SIZE`
`static int`	`MIN_HEADER_SIZE` Persistent fields.
`static int`	`VLSN_OFFSET`

Constructor Summary

Constructors
Constructor and Description
`LogEntryHeader(ByteBuffer entryBuffer, int logVersion, long lsn)` For reading a log entry.
`LogEntryHeader(byte entryType, int entryVersion, int itemSize, VLSN vlsn)` For reading a replication message.
`LogEntryHeader(LogEntry entry, Provisional provisional, ReplicationContext repContext)` For writing a log header.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`ByteBuffer`	`addPostMarshallingInfo(ByteBuffer entryBuffer, long lastOffset, VLSN vlsn)` Add those parts of the header that must be calculated later to the entryBuffer, and also assign the fields in this class.
`void`	`dumpLog(StringBuilder sb, boolean verbose)`
`void`	`dumpRep(StringBuilder sb)`
`long`	`getChecksum()`
`int`	`getEntrySize()`
`int`	`getItemSize()`
`long`	`getPrevOffset()`
`Provisional`	`getProvisional()`
`boolean`	`getReplicated()`
`int`	`getSize()`
`byte`	`getType()`
`int`	`getVariablePortionSize()`
`int`	`getVersion()`
`VLSN`	`getVLSN()`
`boolean`	`hasChecksum()`
`boolean`	`isErased()` Returns whether the type of this entry has been changed to LOG_ERASED.
`boolean`	`isInvisible()`
`boolean`	`isVariableLength()` May be called after reading MIN_HEADER_SIZE bytes to determine whether more bytes (getVariablePortionSize) should be read.
`boolean`	`logicalEqualsIgnoreVersion(LogEntryHeader other)`
`void`	`readVariablePortion(ByteBuffer entryBuffer)` Assumes this is called directly after the constructor, and that the entryBuffer is positioned right before the VLSN.
`void`	`setFileHeaderVersion(int logVersion)` Called to set the version for a file header entry after reading the version from the item data.
`String`	`toString()`
`static void`	`turnOffInvisible(ByteBuffer buffer, int logHeaderStartPosition)` Turn off the invisible bit in the byte buffer which backs this log entry header.
`void`	`writeToLog(ByteBuffer entryBuffer)` Serialize this object into the buffer and leave the buffer positioned in the right place to write the following item.

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

- Field Detail
  - MIN_HEADER_SIZE
```
public static final int MIN_HEADER_SIZE
```
    Persistent fields. Layout on disk is (invariant) checksum - 4 bytes (invariant) entry type - 1 byte (invariant) entry flags - 1 byte (invariant) offset of previous log entry - 4 bytes (invariant) item size (not counting header size) - 4 bytes (optional) vlsn - 8 bytes Flags: The provisional bit can be set for any log type in the log. It's an indication to recovery that the entry shouldn't be processed when rebuilding the tree. See com.sleepycat.je.log.Provisional.java for the reasons why it's set. The replicated bit is set when this particular log entry is part of the replication stream and contains a VLSN in the header. The invisible bit is set when this log entry has been rolled back as part of replication syncup. The ensuing log entry has not been checksum-corrected, and to read it, the invisible bit must be cloaked. The VLSN_PRESENT bit is set when a VLSN is present for log version 8+, and is set when the replicated bit is *not* set in the case of a cleaner migrated LN. Prior to version 8, the replicated bit alone indicates that a VLSN is present. For all versions, if the replicated bit is set then a VLSN is always present. [#19476] first version of migrated LN a replicated LN --------------- ----------- log version 7- replicated = true replicated = false (JE 4.1 and vlsn present = false vlsn present = false earlier) vlsn exists in header no vlsn in header log version 8+ replicated = true replicated = false preserve record vlsn present = true vlsn present = false version = false vlsn exists in header no vlsn in header log version 8+ replicated = true replicated = false preserve record vlsn present = true vlsn present = true version = true vlsn exists in header vlsn exists in header
    
    See Also:
    
    Constant Field Values
  - MAX_HEADER_SIZE
```
public static final int MAX_HEADER_SIZE
```
    See Also:
    
    Constant Field Values
  - CHECKSUM_BYTES
```
public static final int CHECKSUM_BYTES
```
    See Also:
    
    Constant Field Values
  - ENTRYTYPE_OFFSET
```
public static final int ENTRYTYPE_OFFSET
```
    See Also:
    
    Constant Field Values
  - VLSN_OFFSET
```
public static final int VLSN_OFFSET
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - LogEntryHeader
```
public LogEntryHeader(ByteBuffer entryBuffer,
                      int logVersion,
                      long lsn)
               throws ChecksumException
```
    For reading a log entry.
    
    Parameters:
    
    entryBuffer - the buffer containing at least the first MIN_HEADER_SIZE bytes of the entry header.
    
    logVersion - is the log version of the file that contains the given buffer, and is obtained from the file header. Note that for the file header entry itself, UNKNOWN_FILE_HEADER_VERSION may be passed.
    
    lsn - is the LSN of the entry, for exception reporting.
    
    Throws:
    
    ChecksumException
  - LogEntryHeader
```
public LogEntryHeader(LogEntry entry,
                      Provisional provisional,
                      ReplicationContext repContext)
```
    For writing a log header. public for unit tests.
  - LogEntryHeader
```
public LogEntryHeader(byte entryType,
                      int entryVersion,
                      int itemSize,
                      VLSN vlsn)
```
    For reading a replication message. The node-specific parts of the header are not needed.
- Method Detail
  - setFileHeaderVersion
```
public void setFileHeaderVersion(int logVersion)
```
    Called to set the version for a file header entry after reading the version from the item data. See FileHeaderEntry.readEntry. [#16939]
  - getChecksum
```
public long getChecksum()
```
  - getType
```
public byte getType()
```
  - getVersion
```
public int getVersion()
```
  - getPrevOffset
```
public long getPrevOffset()
```
  - getItemSize
```
public int getItemSize()
```
  - getEntrySize
```
public int getEntrySize()
```
  - getVLSN
```
public VLSN getVLSN()
```
  - getReplicated
```
public boolean getReplicated()
```
  - getProvisional
```
public Provisional getProvisional()
```
  - isInvisible
```
public boolean isInvisible()
```
  - isErased
```
public boolean isErased()
```
    Returns whether the type of this entry has been changed to LOG_ERASED.
    
    See Also:
    
    ErasedLogEntry, DataEraser
  - hasChecksum
```
public boolean hasChecksum()
```
  - getVariablePortionSize
```
public int getVariablePortionSize()
```
  - getSize
```
public int getSize()
```
    Returns:
    
    number of bytes used to store this header
  - readVariablePortion
```
public void readVariablePortion(ByteBuffer entryBuffer)
```
    Assumes this is called directly after the constructor, and that the entryBuffer is positioned right before the VLSN.
  - writeToLog
```
public void writeToLog(ByteBuffer entryBuffer)
```
    Serialize this object into the buffer and leave the buffer positioned in the right place to write the following item. The checksum, prevEntry, and vlsn values will filled in later on. public for unit tests.
  - addPostMarshallingInfo
```
public ByteBuffer addPostMarshallingInfo(ByteBuffer entryBuffer,
                                         long lastOffset,
                                         VLSN vlsn)
```
    Add those parts of the header that must be calculated later to the entryBuffer, and also assign the fields in this class. That's - the prev offset, which must be done within the log write latch to be sure what that lsn is - the VLSN, for the same reason - the checksumVal, which must be added last, after all other fields are marshalled. (public for unit tests)
  - dumpLog
```
public void dumpLog(StringBuilder sb,
                    boolean verbose)
```
    Parameters:
    
    sb - destination string buffer
    
    verbose - if true, dump the full, verbose version
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - dumpRep
```
public void dumpRep(StringBuilder sb)
```
  - logicalEqualsIgnoreVersion
```
public boolean logicalEqualsIgnoreVersion(LogEntryHeader other)
```
    Returns:
    
    true if two log headers are logically the same. This check will ignore the log version. Used by replication.
  - isVariableLength
```
public boolean isVariableLength()
```
    May be called after reading MIN_HEADER_SIZE bytes to determine whether more bytes (getVariablePortionSize) should be read.
  - turnOffInvisible
```
public static void turnOffInvisible(ByteBuffer buffer,
                                    int logHeaderStartPosition)
```
    Turn off the invisible bit in the byte buffer which backs this log entry header.
    
    Parameters:
    
    logHeaderStartPosition - the byte position of the start of the log entry header.

Class LogEntryHeader

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MIN_HEADER_SIZE

MAX_HEADER_SIZE

CHECKSUM_BYTES

ENTRYTYPE_OFFSET

VLSN_OFFSET

Constructor Detail

LogEntryHeader

LogEntryHeader

LogEntryHeader

Method Detail

setFileHeaderVersion

getChecksum

getType

getVersion

getPrevOffset

getItemSize

getEntrySize

getVLSN

getReplicated

getProvisional

isInvisible

isErased

hasChecksum

getVariablePortionSize

getSize

readVariablePortion

writeToLog

addPostMarshallingInfo

dumpLog

toString

dumpRep

logicalEqualsIgnoreVersion

isVariableLength

turnOffInvisible