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. See also the class comment of SegmentWriter.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	WriteOperationHandler.WriteOperation A WriteOperation encapsulates an operation on a SegmentWriter.

Constructor Summary

Constructors

Constructor and Description
SegmentBufferWriter(SegmentStore store, com.google.common.base.Supplier<Integer> segmentCounter, SegmentReader reader, String wid, int generation)

Method Summary

Modifier and Type	Method and Description
RecordId	execute(WriteOperationHandler.WriteOperation writeOperation) Execute the passed writeOperation by passing it a SegmentBufferWriter.
void	flush() Adds a segment header to the buffer and writes a segment to the segment store.
RecordId	prepare(RecordType type, int size, Collection<RecordId> ids) 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.
void	writeByte(byte value)
void	writeBytes(byte[] data, int offset, int length)
void	writeInt(int value)
void	writeLong(long value)
void	writeRecordId(RecordId recordId) Write a record id, and marks the record id as referenced (removes it from the unreferenced set).
void	writeRecordId(RecordId recordId, boolean reference) Write a record ID.
void	writeShort(short value)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SegmentBufferWriter

public SegmentBufferWriter(@Nonnull
                           SegmentStore store,
                           @Nonnull
                           com.google.common.base.Supplier<Integer> segmentCounter,
                           @Nonnull
                           SegmentReader reader,
                           @CheckForNull
                           String wid,
                           int generation)

Method Detail

execute

@Nonnull
public RecordId execute(@Nonnull
                                 WriteOperationHandler.WriteOperation writeOperation)
                          throws IOException

Execute the passed writeOperation by passing it a SegmentBufferWriter.

Parameters:

writeOperation - WriteOperationHandler.WriteOperation to execute

Returns:

RecordId that resulted from persisting the changes.

Throws:

IOException

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, and marks the record id as referenced (removes it from the unreferenced set).

Parameters:

recordId - the record id

writeRecordId

public void writeRecordId(RecordId recordId,
                          boolean reference)

Write a record ID. Optionally, mark this record ID as being a reference. If a record ID is marked as a reference, the referenced record can't be a root record in this segment.

Parameters:

recordId - the record ID.

reference - true if this record ID is a reference, false otherwise.

writeBytes

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

flush

public void flush()
           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)
                 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

Returns:

a new record id

Throws:

IOException