org.apache.lucene.util
Class ByteBlockPool

java.lang.Object
  org.apache.lucene.util.ByteBlockPool

public final class ByteBlockPool
extends Object

Class that Posting and PostingVector use to write byte streams into shared fixed-size byte[] arrays. The idea is to allocate slices of increasing lengths For example, the first slice is 5 bytes, the next slice is 14, etc. We start by writing our bytes into the first 5 bytes. When we hit the end of the slice, we allocate the next slice and then write the address of the new slice into the last 4 bytes of the previous slice (the "forwarding address"). Each slice is filled with 0's initially, and we mark the end with a non-zero byte. This way the methods that are writing into the slice don't need to record its length and instead allocate a new slice once they hit a non-zero byte.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary

static class	ByteBlockPool.Allocator Abstract class for allocating and freeing byte blocks.
static class	ByteBlockPool.DirectAllocator A simple ByteBlockPool.Allocator that never recycles.
static class	ByteBlockPool.DirectTrackingAllocator A simple ByteBlockPool.Allocator that never recycles, but tracks how much total RAM is in use.

Field Summary

byte[]	buffer Current head buffer
byte[][]	buffers
static int	BYTE_BLOCK_MASK
static int	BYTE_BLOCK_SHIFT
static int	BYTE_BLOCK_SIZE
int	byteOffset Current head offset
int	byteUpto Where we are in head buffer
static int	FIRST_LEVEL_SIZE
static int[]	levelSizeArray
static int[]	nextLevelArray

Constructor Summary

ByteBlockPool(ByteBlockPool.Allocator allocator)

Method Summary

int	allocSlice(byte[] slice, int upto)
void	copy(BytesRef bytes) Copies the given BytesRef at the current positions ( byteUpto across buffer boundaries
BytesRef	copyFrom(BytesRef bytes)
BytesRef	deref(BytesRef bytes) Dereferences the byte block according to BytesRef offset.
void	dropBuffersAndReset()
int	newSlice(int size)
void	nextBuffer()
void	reset()
BytesRef	setBytesRef(BytesRef term, int textStart)
void	writePool(DataOutput out) Writes the pools content to the given DataOutput

Methods inherited from class java.lang.Object

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

Field Detail

BYTE_BLOCK_SHIFT

public static final int BYTE_BLOCK_SHIFT

See Also:

Constant Field Values

BYTE_BLOCK_SIZE

public static final int BYTE_BLOCK_SIZE

See Also:

Constant Field Values

BYTE_BLOCK_MASK

public static final int BYTE_BLOCK_MASK

See Also:

Constant Field Values

buffers

public byte[][] buffers

byteUpto

public int byteUpto

Where we are in head buffer

buffer

public byte[] buffer

Current head buffer

byteOffset

public int byteOffset

Current head offset

nextLevelArray

public static final int[] nextLevelArray

levelSizeArray

public static final int[] levelSizeArray

FIRST_LEVEL_SIZE

public static final int FIRST_LEVEL_SIZE

Constructor Detail

ByteBlockPool

public ByteBlockPool(ByteBlockPool.Allocator allocator)

Method Detail

dropBuffersAndReset

public void dropBuffersAndReset()

reset

public void reset()

nextBuffer

public void nextBuffer()

newSlice

public int newSlice(int size)

allocSlice

public int allocSlice(byte[] slice,
                      int upto)

setBytesRef

public final BytesRef setBytesRef(BytesRef term,
                                  int textStart)

deref

public final BytesRef deref(BytesRef bytes)

Dereferences the byte block according to BytesRef offset. The offset is interpreted as the absolute offset into the ByteBlockPool.

copy

public final void copy(BytesRef bytes)

Copies the given BytesRef at the current positions ( byteUpto across buffer boundaries

copyFrom

public final BytesRef copyFrom(BytesRef bytes)

writePool

public final void writePool(DataOutput out)
                     throws IOException

Writes the pools content to the given DataOutput

Throws:

IOException