Package org.apache.jackrabbit.oak.segment

Class SegmentBufferWriter

java.lang.Object
org.apache.jackrabbit.oak.segment.SegmentBufferWriter
public class SegmentBufferWriter extends Object
This class encapsulates the state of a segment being written. It provides methods for writing primitive data types and for pre-allocating buffer space in the current segment. Should the current segment not have enough space left the current segment is flushed and a fresh one is allocated.

The common usage pattern is: 

    SegmentBufferWriter writer = ...
    writer.prepare(...)  // allocate buffer
    writer.writeXYZ(...)
The behaviour of this class is undefined should the pre-allocated buffer be overrun be calling any of the write methods.

Instances of this class are not thread safe

  • Constructor Details

    • SegmentBufferWriter

      public SegmentBufferWriter(@NotNull @NotNull SegmentIdProvider idProvider, @Nullable @Nullable String wid, @NotNull @NotNull GCGeneration gcGeneration)

  • Method Details

    • execute

      @NotNull public @NotNull RecordId execute(@NotNull @NotNull GCGeneration gcGeneration, @NotNull @NotNull org.apache.jackrabbit.oak.segment.WriteOperationHandler.WriteOperation writeOperation) throws IOException
      Throws:
      IOException

    • getGCGeneration

      @NotNull public @NotNull GCGeneration getGCGeneration()

    • writeByte

      public void writeByte(byte value)

    • writeShort

      public void writeShort(short value)

    • writeInt

      public void writeInt(int value)

    • writeLong

      public void writeLong(long value)

    • writeRecordId

      public void writeRecordId(RecordId recordId)
      Write a record ID.
      Parameters:
      recordId - the record ID.

    • writeBytes

      public void writeBytes(byte[] data, int offset, int length)

    • flush

      public void flush(@NotNull @NotNull SegmentStore store) throws IOException
      Adds a segment header to the buffer and writes a segment to the segment store. This is done automatically (called from prepare) when there is not enough space for a record. It can also be called explicitly.
      Throws:
      IOException

    • prepare

      public RecordId prepare(RecordType type, int size, Collection<RecordId> ids, SegmentStore store) throws IOException
      Before writing a record (which are written backwards, from the end of the file to the beginning), this method is called, to ensure there is enough space. A new segment is also created if there is not enough space in the segment lookup table or elsewhere.

      This method does not actually write into the segment, just allocates the space (flushing the segment if needed and starting a new one), and sets the write position (records are written from the end to the beginning, but within a record from left to right).

      Parameters:
      type - the record type (only used for root records)
      size - the size of the record, excluding the size used for the record ids
      ids - the record ids
      store - the SegmentStore instance to write full segments to
      Returns:
      a new record id
      Throws:
      IOException