Package 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.

  • Field Details

  • Method Details

    • newSegmentData

      static SegmentData newSegmentData(Buffer buffer)

    • newRawSegmentData

      static SegmentData newRawSegmentData(Buffer buffer)

    • getVersion

      byte getVersion()

    • getSignature

      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

      default long readLength(int recordReferenceOffset)

    • readString

      default StringData readString(int recordReferenceOffset)

    • readRecordId

      default 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(OutputStream stream) throws IOException
      Throws:
      IOException

    • binDump

      void binDump(OutputStream stream) throws IOException
      Throws:
      IOException

    • estimateMemoryUsage

      int estimateMemoryUsage()