org.apache.jackrabbit.oak.segment.data

Interface SegmentData

public interface SegmentData

Access the data of a segment.

A segment is composed of a header and the proper data. The header has a fixed- and a variable-length part.

The fixed-length part of the header contains a signature, which is a string that uniquely identifies the rest of the content as a segment; a getVersion(), which specifies the version of the binary format used to serialize the content of the segment; a full generation, which describes the generation of the segment with regards to full compaction; a generation, which identifies the generation of the segment with regards to full or tail compaction; a compacted flag, which determines if the segment was written by a compaction operation; the number of record references, which is the number of record entries in the segment; the number of segment references, which is the number of identifiers of other segments used by this segment.

The variable part of the header contains the list of segment references and the list of record references. A segment references is composed by the most significant bits and lsb of the segment identifier. A record reference is composed of a record number, a record type and a record offset.

The most prominent use for a segment is to hold record data. Many methods of this class allows access to the record data. These methods accept an integer representing an absolute position pointing to the record data. The absolute position, though, is virtual: it is computed on a virtual segment 256K long. This offset is usually obtained by accessing the record offset of a record reference entry. The class will normalize the offset for the actual size of the segment, which can be smaller than 256K. It is acceptable to displace the offset of a record reference entry by a positive amount. This can be useful to access a field of a composite record saved at a specific offset.

Method Summary

Modifier and Type	Method and Description
void	binDump(java.io.OutputStream stream)
int	estimateMemoryUsage()
int	getFullGeneration()
int	getGeneration()
int	getRecordReferenceNumber(int i)
int	getRecordReferenceOffset(int i)
int	getRecordReferencesCount()
byte	getRecordReferenceType(int i)
long	getSegmentReferenceLsb(int i)
long	getSegmentReferenceMsb(int i)
int	getSegmentReferencesCount()
java.lang.String	getSignature()
byte	getVersion()
void	hexDump(java.io.OutputStream stream)
boolean	isCompacted()
static SegmentData	newRawSegmentData(Buffer buffer)
static SegmentData	newSegmentData(Buffer buffer)
byte	readByte(int recordReferenceOffset)
Buffer	readBytes(int recordReferenceOffset, int size)
int	readInt(int recordReferenceOffset)
long	readLength(int recordReferenceOffset)
long	readLong(int recordReferenceOffset)
RecordIdData	readRecordId(int recordReferenceOffset)
short	readShort(int recordReferenceOffset)
StringData	readString(int recordReferenceOffset)
int	size()

Method Detail

newSegmentData

static SegmentData newSegmentData(Buffer buffer)

newRawSegmentData

static SegmentData newRawSegmentData(Buffer buffer)

getVersion

byte getVersion()

getSignature

java.lang.String getSignature()

getFullGeneration

int getFullGeneration()

isCompacted

boolean isCompacted()

getGeneration

int getGeneration()

getSegmentReferencesCount

int getSegmentReferencesCount()

getRecordReferencesCount

int getRecordReferencesCount()

getRecordReferenceNumber

int getRecordReferenceNumber(int i)

getRecordReferenceType

byte getRecordReferenceType(int i)

getRecordReferenceOffset

int getRecordReferenceOffset(int i)

getSegmentReferenceMsb

long getSegmentReferenceMsb(int i)

getSegmentReferenceLsb

long getSegmentReferenceLsb(int i)

readLength

long readLength(int recordReferenceOffset)

readString

StringData readString(int recordReferenceOffset)

readRecordId

RecordIdData readRecordId(int recordReferenceOffset)

readByte

byte readByte(int recordReferenceOffset)

readInt

int readInt(int recordReferenceOffset)

readShort

short readShort(int recordReferenceOffset)

readLong

long readLong(int recordReferenceOffset)

readBytes

Buffer readBytes(int recordReferenceOffset,
                 int size)

size

int size()

hexDump

void hexDump(java.io.OutputStream stream)
      throws java.io.IOException

Throws:

java.io.IOException

binDump

void binDump(java.io.OutputStream stream)
      throws java.io.IOException

Throws:

java.io.IOException

estimateMemoryUsage

int estimateMemoryUsage()