org.apache.hadoop.hbase.io.encoding

Interface DataBlockEncoder

All Known Implementing Classes:

CopyKeyDataBlockEncoder, DiffKeyDeltaEncoder, FastDiffDeltaEncoder, PrefixKeyDeltaEncoder

@InterfaceAudience.Private
public interface DataBlockEncoder

Encoding of KeyValue. It aims to be fast and efficient using assumptions:

• the KeyValues are stored sorted by key
• we know the structure of KeyValue
• the values are always iterated forward from beginning of block
• knowledge of Key Value format

It is designed to work fast enough to be feasible as in memory compression.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	DataBlockEncoder.EncodedSeeker An interface which enable to seek while underlying data is encoded.

Method Summary

Methods

Modifier and Type	Method and Description
DataBlockEncoder.EncodedSeeker	createSeeker(KeyValue.KVComparator comparator, HFileBlockDecodingContext decodingCtx) Create a HFileBlock seeker which find KeyValues within a block.
ByteBuffer	decodeKeyValues(DataInputStream source, HFileBlockDecodingContext decodingCtx) Decode.
int	encode(Cell cell, HFileBlockEncodingContext encodingCtx, DataOutputStream out) Encodes a KeyValue.
void	endBlockEncoding(HFileBlockEncodingContext encodingCtx, DataOutputStream out, byte[] uncompressedBytesWithHeader) Ends encoding for a block of KeyValues.
ByteBuffer	getFirstKeyInBlock(ByteBuffer block) Return first key in block.
HFileBlockDecodingContext	newDataBlockDecodingContext(HFileContext meta) Creates an encoder specific decoding context, which will prepare the data before actual decoding
HFileBlockEncodingContext	newDataBlockEncodingContext(DataBlockEncoding encoding, byte[] headerBytes, HFileContext meta) Creates a encoder specific encoding context
void	startBlockEncoding(HFileBlockEncodingContext encodingCtx, DataOutputStream out) Starts encoding for a block of KeyValues.

Method Detail

startBlockEncoding

void startBlockEncoding(HFileBlockEncodingContext encodingCtx,
                      DataOutputStream out)
                        throws IOException

Starts encoding for a block of KeyValues. Call endBlockEncoding(HFileBlockEncodingContext, DataOutputStream, byte[]) to finish encoding of a block.

Parameters:

encodingCtx -

out -

Throws:

IOException

encode

int encode(Cell cell,
         HFileBlockEncodingContext encodingCtx,
         DataOutputStream out)
           throws IOException

Encodes a KeyValue.

Parameters:

cell -

encodingCtx -

out -

Returns:

unencoded kv size written

Throws:

IOException

endBlockEncoding

void endBlockEncoding(HFileBlockEncodingContext encodingCtx,
                    DataOutputStream out,
                    byte[] uncompressedBytesWithHeader)
                      throws IOException

Ends encoding for a block of KeyValues. Gives a chance for the encoder to do the finishing stuff for the encoded block. It must be called at the end of block encoding.

Parameters:

encodingCtx -

out -

uncompressedBytesWithHeader -

Throws:

IOException

decodeKeyValues

ByteBuffer decodeKeyValues(DataInputStream source,
                         HFileBlockDecodingContext decodingCtx)
                           throws IOException

Decode.

Parameters:

source - Compressed stream of KeyValues.

decodingCtx -

Returns:

Uncompressed block of KeyValues.

Throws:

IOException - If there is an error in source.

getFirstKeyInBlock

ByteBuffer getFirstKeyInBlock(ByteBuffer block)

Return first key in block. Useful for indexing. Typically does not make a deep copy but returns a buffer wrapping a segment of the actual block's byte array. This is because the first key in block is usually stored unencoded.

Parameters:

block - encoded block we want index, the position will not change

Returns:

First key in block.

createSeeker

DataBlockEncoder.EncodedSeeker createSeeker(KeyValue.KVComparator comparator,
                                          HFileBlockDecodingContext decodingCtx)

Create a HFileBlock seeker which find KeyValues within a block.

Parameters:

comparator - what kind of comparison should be used

decodingCtx -

Returns:

A newly created seeker.

newDataBlockEncodingContext

HFileBlockEncodingContext newDataBlockEncodingContext(DataBlockEncoding encoding,
                                                    byte[] headerBytes,
                                                    HFileContext meta)

Creates a encoder specific encoding context

Parameters:

encoding - encoding strategy used

headerBytes - header bytes to be written, put a dummy header here if the header is unknown

meta - HFile meta data

Returns:

a newly created encoding context

newDataBlockDecodingContext

HFileBlockDecodingContext newDataBlockDecodingContext(HFileContext meta)

Creates an encoder specific decoding context, which will prepare the data before actual decoding

Parameters:

meta - HFile meta data

Returns:

a newly created decoding context