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HBASE-14573 Edit on the ByteBufferedCell javadoc

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stack 2015-10-07 11:31:15 -07:00
parent d80c7e95ec
commit 4e876c59f4
1 changed files with 21 additions and 8 deletions
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29
hbase-common/src/main/java/org/apache/hadoop/hbase/ByteBufferedCell.java
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@ -22,17 +22,30 @@ import java.nio.ByteBuffer;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
/**
* This class is a server side extension to the Cell interface. This is used when the actual Cell
* implementation is backed by {@link ByteBuffer}. This class contain ByteBuffer backed getters for
* row, cf, qualifier, value and tags. Also getters of the position where these field bytes begin. A
* cell object can be of this type only in server side. When the object is of this type, use the
* getXXXByteBuffer() method along with getXXXPositionInByteBuffer(). If cell is backed by off heap
* ByteBuffer the call to getXXXArray() will result is temporary byte array creation and bytes copy
* resulting in lot of garbage.
* This class is a server side extension to the {@link Cell} interface. It is used when the
* Cell is backed by a {@link ByteBuffer}: i.e. <code>cell instanceof ByteBufferedCell</code>.
*
* <p>This class has getters for the row, column family, column qualifier, value and tags hosting
* ByteBuffers. It also has getters of the *position* within a ByteBuffer where these
* field bytes begin. These are needed because a single ByteBuffer may back one or many Cell
* instances -- it depends on the implementation -- so the ByteBuffer position as returned by
* {@link ByteBuffer#arrayOffset()} cannot be relied upon. Also, do not confuse these position
* methods with the getXXXOffset methods from the super Interface, {@link Cell}; dependent up on
* implementation, the Cell getXXXOffset methods can return the same value as a call to its
* equivalent position method from below BUT they can also stray; if a ByteBufferedCell, use the
* below position methods to find where a field begins.
*
* <p>Use the getXXXLength methods from Cell to find a fields length.
*
* <p>A Cell object can be of this type only on the server side.
*
* <p>WARNING: If a Cell is backed by an offheap ByteBuffer, any call to getXXXArray() will result
* in a temporary byte array creation and a bytes copy. Avoid these allocations by using the
* appropriate Cell access server-side: i.e. ByteBufferedCell when backed by a ByteBuffer and Cell
* when it is not.
*/
@InterfaceAudience.Private
public abstract class ByteBufferedCell implements Cell {
/**
* @return The {@link ByteBuffer} containing the row bytes.
*/