Package org.apache.lucene.util
Class ByteBlockPool
java.lang.Object
org.apache.lucene.util.ByteBlockPool
- All Implemented Interfaces:
Accountable
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.
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Nested Class Summary
Modifier and TypeClassDescriptionstatic class
Abstract class for allocating and freeing byte blocks.static final class
A simpleByteBlockPool.Allocator
that never recycles.static class
A simpleByteBlockPool.Allocator
that never recycles, but tracks how much total RAM is in use. -
Field Summary
Modifier and TypeFieldDescriptionbyte[]
Current head bufferbyte[][]
array of buffers currently used in the pool.static final int
static final int
static final int
int
Current head offsetint
Where we are in head bufferstatic final int
The first level size for new slicesstatic final int[]
An array holding the level sizes for byte slices.static final int[]
An array holding the offset into theLEVEL_SIZE_ARRAY
to quickly navigate to the next slice level.Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionint
allocSlice
(byte[] slice, int upto) Creates a new byte slice with the given starting size and returns the slices offset in the pool.void
Appends the bytes in the providedBytesRef
at the current position.int
newSlice
(int size) Allocates a new slice with the given size.void
Advances the pool to its next buffer.long
Return the memory usage of this object in bytes.void
readBytes
(long offset, byte[] bytes, int bytesOffset, int bytesLength) Reads bytes out of the pool starting at the given offset with the given length into the given byte array at offsetoff
.void
reset()
Resets the pool to its initial state reusing the first buffer and fills all buffers with0
bytes before they reused or passed toByteBlockPool.Allocator.recycleByteBlocks(byte[][], int, int)
.void
reset
(boolean zeroFillBuffers, boolean reuseFirst) Expert: Resets the pool to its initial state reusing the first buffer.void
setBytesRef
(BytesRef term, int textStart) void
setRawBytesRef
(BytesRef ref, long offset) Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface org.apache.lucene.util.Accountable
getChildResources
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Field Details
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BYTE_BLOCK_SHIFT
public static final int BYTE_BLOCK_SHIFT- See Also:
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BYTE_BLOCK_SIZE
public static final int BYTE_BLOCK_SIZE- See Also:
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BYTE_BLOCK_MASK
public static final int BYTE_BLOCK_MASK- See Also:
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buffers
public byte[][] buffersarray of buffers currently used in the pool. Buffers are allocated if needed don't modify this outside of this class. -
byteUpto
public int byteUptoWhere we are in head buffer -
buffer
public byte[] bufferCurrent head buffer -
byteOffset
public int byteOffsetCurrent head offset -
NEXT_LEVEL_ARRAY
public static final int[] NEXT_LEVEL_ARRAYAn array holding the offset into theLEVEL_SIZE_ARRAY
to quickly navigate to the next slice level. -
LEVEL_SIZE_ARRAY
public static final int[] LEVEL_SIZE_ARRAYAn array holding the level sizes for byte slices. -
FIRST_LEVEL_SIZE
public static final int FIRST_LEVEL_SIZEThe first level size for new slices- See Also:
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Constructor Details
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ByteBlockPool
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Method Details
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reset
public void reset()Resets the pool to its initial state reusing the first buffer and fills all buffers with0
bytes before they reused or passed toByteBlockPool.Allocator.recycleByteBlocks(byte[][], int, int)
. CallingnextBuffer()
is not needed after reset. -
reset
public void reset(boolean zeroFillBuffers, boolean reuseFirst) Expert: Resets the pool to its initial state reusing the first buffer. CallingnextBuffer()
is not needed after reset.- Parameters:
zeroFillBuffers
- iftrue
the buffers are filled with0
. This should be set totrue
if this pool is used with slices.reuseFirst
- iftrue
the first buffer will be reused and callingnextBuffer()
is not needed after reset iff the block pool was used before ie.nextBuffer()
was called before.
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nextBuffer
public void nextBuffer()Advances the pool to its next buffer. This method should be called once after the constructor to initialize the pool. In contrast to the constructor areset()
call will advance the pool to its first buffer immediately. -
newSlice
public int newSlice(int size) Allocates a new slice with the given size.- See Also:
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allocSlice
public int allocSlice(byte[] slice, int upto) Creates a new byte slice with the given starting size and returns the slices offset in the pool. -
setBytesRef
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append
Appends the bytes in the providedBytesRef
at the current position. -
readBytes
public void readBytes(long offset, byte[] bytes, int bytesOffset, int bytesLength) Reads bytes out of the pool starting at the given offset with the given length into the given byte array at offsetoff
.Note: this method allows to copy across block boundaries.
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setRawBytesRef
Set the givenBytesRef
so that its content is equal to theref.length
bytes starting atoffset
. Most of the time this method will set pointers to internal data-structures. However, in case a value crosses a boundary, a fresh copy will be returned. On the contrary tosetBytesRef(BytesRef, int)
, this does not expect the length to be encoded with the data. -
ramBytesUsed
public long ramBytesUsed()Description copied from interface:Accountable
Return the memory usage of this object in bytes. Negative values are illegal.- Specified by:
ramBytesUsed
in interfaceAccountable
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