Package org.apache.druid.segment.data

Class CompressedBlockReader

java.lang.Object

org.apache.druid.segment.data.CompressedBlockReader

All Implemented Interfaces:

Closeable, AutoCloseable

public final class CompressedBlockReader
extends Object
implements Closeable

Reader for a virtual contiguous address range backed by compressed blocks of data. Format: | version (byte) | compression (byte) | block size (int) | num blocks (int) | end offsets | compressed data | This mechanism supports two modes of use, the first where callers may ask for a range of data from the underlying blocks, provided by getRange(long, int). The ByteBuffer provided by this method may or may not be valid after additional calls to getRange(long, int) or calls to seekBlock(int). For fixed width values which are aligned with the block size, callers may also use the method getDecompressedDataBuffer() to have direct access to the current uncompressed block, and use the methods loadBlock(long) to load the correct block and translate a virtual offset into the relative offset, or seekBlock(int) to change which block is currently loaded. getRange(long, int) uses these same mechanisms internally to supply data.

See Also:

for writer

Field Summary

Fields

Modifier and Type	Field	Description
static byte	VERSION

Constructor Summary

Constructors

Constructor	Description
CompressedBlockReader(CompressionStrategy compressionStrategy, int numBlocks, int blockSize, IntBuffer endOffsetsBuffer, ByteBuffer compressedDataBuffer, ByteOrder byteOrder)

Method Summary

Modifier and Type	Method	Description
void	close()
static Supplier<CompressedBlockReader>	fromByteBuffer(ByteBuffer buffer, ByteOrder byteOrder)
int	getCurrentBlockNumber()	Get current block number of data loaded in decompressedDataBuffer
ByteBuffer	getDecompressedDataBuffer()	Current decompressed data buffer of the data located in currentBlockNumber
ByteBuffer	getRange(long startOffset, int size)	Get ByteBuffer containing data from starting offset of contiguous virtual address range of the specified size.
long	getSize()	Get size in bytes of virtual contiguous buffer
int	loadBlock(long startOffset)	Load the block for the specified virtual offset, returning the relative offset into decompressedDataBuffer of the currentBlockNumber.
void	seekBlock(int block)	Swap the current data in decompressedDataBuffer to the specified block

Methods inherited from class java.lang.Object

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

Field Detail

VERSION

public static final byte VERSION

See Also:

Constant Field Values

Constructor Detail

CompressedBlockReader

public CompressedBlockReader(CompressionStrategy compressionStrategy,
                             int numBlocks,
                             int blockSize,
                             IntBuffer endOffsetsBuffer,
                             ByteBuffer compressedDataBuffer,
                             ByteOrder byteOrder)

Method Detail

fromByteBuffer

public static Supplier<CompressedBlockReader> fromByteBuffer(ByteBuffer buffer,
                                                             ByteOrder byteOrder)

getSize

public long getSize()

Get size in bytes of virtual contiguous buffer

getCurrentBlockNumber

public int getCurrentBlockNumber()

Get current block number of data loaded in decompressedDataBuffer

getDecompressedDataBuffer

public ByteBuffer getDecompressedDataBuffer()

Current decompressed data buffer of the data located in currentBlockNumber

getRange

public ByteBuffer getRange(long startOffset,
                           int size)

Get ByteBuffer containing data from starting offset of contiguous virtual address range of the specified size. If this data spans more than a single block, it will be copied on heap, but if not, will be a view into decompressedDataBuffer. The data returned by this method is not guaranteed to still be readable after another call to getRange(long, int) or a call to seekBlock(int).

loadBlock

public int loadBlock(long startOffset)

Load the block for the specified virtual offset, returning the relative offset into decompressedDataBuffer of the currentBlockNumber.

seekBlock

public void seekBlock(int block)

Swap the current data in decompressedDataBuffer to the specified block

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException