org.apache.hadoop.hbase.io.hfile

Class HFileBlock.Writer

java.lang.Object

org.apache.hadoop.hbase.io.hfile.HFileBlock.Writer

Direct Known Subclasses:

TestHFileBlockCompatibility.Writer

Enclosing class:

HFileBlock

public static class HFileBlock.Writer
extends Object

Unified version 2 HFile block writer. The intended usage pattern is as follows:

1. Construct an HFileBlock.Writer, providing a compression algorithm.
2. Call startWriting(org.apache.hadoop.hbase.io.hfile.BlockType) and get a data stream to write to.
3. Write your data into the stream.
4. Call writeHeaderAndData(FSDataOutputStream) as many times as you need to. store the serialized block into an external stream.
5. Repeat to write more blocks.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	HFileBlock.Writer.BufferGrabbingByteArrayOutputStream

Constructor Summary

Constructors

Constructor and Description
Writer(HFileDataBlockEncoder dataBlockEncoder, HFileContext fileContext)

Method Summary

Modifier and Type	Method and Description
int	blockSizeWritten() Returns the number of bytes written into the current block so far, or zero if not writing the block at the moment.
protected void	finishBlockAndWriteHeaderAndData(DataOutputStream out) Writes the header and the compressed data of this block (or uncompressed data when not using compression) into the given stream.
HFileBlock	getBlockForCaching(CacheConfig cacheConf) Creates a new HFileBlock.
boolean	isWriting()
void	release() Releases resources used by this writer.
DataOutputStream	startWriting(BlockType newBlockType) Starts writing into the block.
void	write(Cell cell) Writes the Cell to this block
void	writeBlock(HFileBlock.BlockWritable bw, FSDataOutputStream out) Takes the given HFileBlock.BlockWritable instance, creates a new block of its appropriate type, writes the writable into this block, and flushes the block into the output stream.
void	writeHeaderAndData(FSDataOutputStream out) Similar to writeHeaderAndData(FSDataOutputStream), but records the offset of this block so that it can be referenced in the next block of the same type.

Methods inherited from class java.lang.Object

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

Constructor Detail

Writer

public Writer(HFileDataBlockEncoder dataBlockEncoder,
              HFileContext fileContext)

Parameters:

dataBlockEncoder - data block encoding algorithm to use

Method Detail

startWriting

public DataOutputStream startWriting(BlockType newBlockType)
                              throws IOException

Starts writing into the block. The previous block's data is discarded.

Returns:

the stream the user can write their data into

Throws:

IOException

write

public void write(Cell cell)
           throws IOException

Writes the Cell to this block

Parameters:

cell -

Throws:

IOException

writeHeaderAndData

public void writeHeaderAndData(FSDataOutputStream out)
                        throws IOException

Similar to writeHeaderAndData(FSDataOutputStream), but records the offset of this block so that it can be referenced in the next block of the same type.

Parameters:

out -

Throws:

IOException

finishBlockAndWriteHeaderAndData

protected void finishBlockAndWriteHeaderAndData(DataOutputStream out)
                                         throws IOException

Writes the header and the compressed data of this block (or uncompressed data when not using compression) into the given stream. Can be called in the "writing" state or in the "block ready" state. If called in the "writing" state, transitions the writer to the "block ready" state.

Parameters:

out - the output stream to write the

Throws:

IOException

release

public void release()

Releases resources used by this writer.

isWriting

public boolean isWriting()

Returns:

true if a block is being written

blockSizeWritten

public int blockSizeWritten()

Returns the number of bytes written into the current block so far, or zero if not writing the block at the moment. Note that this will return zero in the "block ready" state as well.

Returns:

the number of bytes written

writeBlock

public void writeBlock(HFileBlock.BlockWritable bw,
                       FSDataOutputStream out)
                throws IOException

Takes the given HFileBlock.BlockWritable instance, creates a new block of its appropriate type, writes the writable into this block, and flushes the block into the output stream. The writer is instructed not to buffer uncompressed bytes for cache-on-write.

Parameters:

bw - the block-writable object to write as a block

out - the file system output stream

Throws:

IOException

getBlockForCaching

public HFileBlock getBlockForCaching(CacheConfig cacheConf)

Creates a new HFileBlock. Checksums have already been validated, so the byte buffer passed into the constructor of this newly created block does not have checksum data even though the header minor version is MINOR_VERSION_WITH_CHECKSUM. This is indicated by setting a 0 value in bytesPerChecksum.