Package org.apache.lucene.util

Class MSBRadixSorter

java.lang.Object

org.apache.lucene.util.Sorter

org.apache.lucene.util.MSBRadixSorter

Direct Known Subclasses:

StableMSBRadixSorter, StringSorter.MSBStringRadixSorter

public abstract class MSBRadixSorter
extends Sorter

Radix sorter for variable-length strings. This class sorts based on the most significant byte first and falls back to IntroSorter when the size of the buckets to sort becomes small.

This algorithm is NOT stable. Worst-case memory usage is about 2.3 KB.

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

Field Summary

Fields

Modifier and Type	Field	Description
protected static int	HISTOGRAM_SIZE
protected static int	LENGTH_THRESHOLD
protected static int	LEVEL_THRESHOLD
protected int	maxLength

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	MSBRadixSorter(int maxLength)	Sole constructor.

Method Summary

Modifier and Type	Method	Description
protected void	buildHistogram(int prefixCommonBucket, int prefixCommonLen, int from, int to, int k, int[] histogram)	Build an histogram of the k-th characters of values occurring between offsets from and to, using getBucket(int, int).
protected abstract int	byteAt(int i, int k)	Return the k-th byte of the entry at index i, or -1 if its length is less than or equal to k.
protected int	compare(int i, int j)	Compare entries found in slots i and j.
protected int	getBucket(int i, int k)	Return a number for the k-th character between 0 and HISTOGRAM_SIZE.
protected Sorter	getFallbackSorter(int k)	Get a fall-back sorter which may assume that the first k bytes of all compared strings are equal.
protected void	reorder(int from, int to, int[] startOffsets, int[] endOffsets, int k)	Reorder based on start/end offsets for each bucket.
protected boolean	shouldFallback(int from, int to, int l)
void	sort(int from, int to)	Sort the slice which starts at from (inclusive) and ends at to (exclusive).
protected void	sort(int from, int to, int k, int l)

Methods inherited from class org.apache.lucene.util.Sorter

comparePivot, setPivot, swap

Methods inherited from class java.lang.Object

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

Field Detail

LEVEL_THRESHOLD

protected static final int LEVEL_THRESHOLD

See Also:

Constant Field Values

HISTOGRAM_SIZE

protected static final int HISTOGRAM_SIZE

See Also:

Constant Field Values

LENGTH_THRESHOLD

protected static final int LENGTH_THRESHOLD

See Also:

Constant Field Values

maxLength

protected final int maxLength

Constructor Detail

MSBRadixSorter

protected MSBRadixSorter(int maxLength)

Sole constructor.

Parameters:

maxLength - the maximum length of keys, pass Integer.MAX_VALUE if unknown.

Method Detail

byteAt

protected abstract int byteAt(int i,
                              int k)

Return the k-th byte of the entry at index i, or -1 if its length is less than or equal to k. This may only be called with a value of i between 0 included and maxLength excluded.

getFallbackSorter

protected Sorter getFallbackSorter(int k)

Get a fall-back sorter which may assume that the first k bytes of all compared strings are equal.

compare

protected final int compare(int i,
                            int j)

Description copied from class: Sorter

Compare entries found in slots i and j. The contract for the returned value is the same as Comparator.compare(Object, Object).

Specified by:

compare in class Sorter

sort

public void sort(int from,
                 int to)

Description copied from class: Sorter

Sort the slice which starts at from (inclusive) and ends at to (exclusive).

Specified by:

sort in class Sorter

sort

protected void sort(int from,
                    int to,
                    int k,
                    int l)

shouldFallback

protected boolean shouldFallback(int from,
                                 int to,
                                 int l)

getBucket

protected int getBucket(int i,
                        int k)

Return a number for the k-th character between 0 and HISTOGRAM_SIZE.

buildHistogram

protected void buildHistogram(int prefixCommonBucket,
                              int prefixCommonLen,
                              int from,
                              int to,
                              int k,
                              int[] histogram)

Build an histogram of the k-th characters of values occurring between offsets from and to, using getBucket(int, int).

reorder

protected void reorder(int from,
                       int to,
                       int[] startOffsets,
                       int[] endOffsets,
                       int k)

Reorder based on start/end offsets for each bucket. When this method returns, startOffsets and endOffsets are equal.

Parameters:

startOffsets - start offsets per bucket

endOffsets - end offsets per bucket