Package org.apache.lucene.util
Class ByteBlockPool
java.lang.Object
org.apache.lucene.util.ByteBlockPool
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.
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Nested Class Summary
Nested ClassesModifier 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
FieldsModifier 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. -
Constructor Summary
Constructors -
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.void
readBytes
(long offset, byte[] bytes, int off, int length) Reads bytes bytes out of the pool starting at the given offset with the given length into the given byte array at offset off.void
reset()
Resets the pool to its initial state reusing the first buffer and fills all buffers with 0 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)
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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 with 0 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 with 0. 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 off, int length) Reads bytes bytes out of the pool starting at the given offset with the given length into the given byte array at offset off.Note: this method allows to copy across block boundaries.
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