Class Util

Static helper methods.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk
Inheritance
System.Object
Util
Namespace: Lucene.Net.Util.Fst
Assembly: Lucene.Net.dll
Syntax
public sealed class Util : object

Methods

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Get<T>(FST<T>, BytesRef)

Looks up the output for this input, or null if the input is not accepted

Declaration
public static T Get<T>(FST<T> fst, BytesRef input)
Parameters
Type Name Description
FST<T> fst
BytesRef input
Returns
Type Description
T
Type Parameters
Name Description
T
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Get<T>(FST<T>, Int32sRef)

Looks up the output for this input, or null if the input is not accepted.

Declaration
public static T Get<T>(FST<T> fst, Int32sRef input)
Parameters
Type Name Description
FST<T> fst
Int32sRef input
Returns
Type Description
T
Type Parameters
Name Description
T
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GetByOutput(FST<Nullable<Int64>>, Int64)

Reverse lookup (lookup by output instead of by input), in the special case when your FSTs outputs are strictly ascending. This locates the input/output pair where the output is equal to the target, and will return null if that output does not exist.

NOTE: this only works with , only works when the outputs are ascending in order with the inputs. For example, simple ordinals (0, 1, 2, ...), or file offets (when appending to a file) fit this.

Declaration
public static Int32sRef GetByOutput(FST<long?> fst, long targetOutput)
Parameters
Type Name Description
FST<System.Nullable<System.Int64>> fst
System.Int64 targetOutput
Returns
Type Description
Int32sRef
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GetByOutput(FST<Nullable<Int64>>, Int64, FST.BytesReader, FST.Arc<Nullable<Int64>>, FST.Arc<Nullable<Int64>>, Int32sRef)

Expert: like GetByOutput(FST<Nullable<Int64>>, Int64) except reusing FST.BytesReader, initial and scratch Arc, and result.

Declaration
public static Int32sRef GetByOutput(FST<long?> fst, long targetOutput, FST.BytesReader in, FST.Arc<long?> arc, FST.Arc<long?> scratchArc, Int32sRef result)
Parameters
Type Name Description
FST<System.Nullable<System.Int64>> fst
System.Int64 targetOutput
FST.BytesReader in
FST.Arc<System.Nullable<System.Int64>> arc
FST.Arc<System.Nullable<System.Int64>> scratchArc
Int32sRef result
Returns
Type Description
Int32sRef
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ReadCeilArc<T>(Int32, FST<T>, FST.Arc<T>, FST.Arc<T>, FST.BytesReader)

Reads the first arc greater or equal that the given label into the provided arc in place and returns it iff found, otherwise return null.

Declaration
public static FST.Arc<T> ReadCeilArc<T>(int label, FST<T> fst, FST.Arc<T> follow, FST.Arc<T> arc, FST.BytesReader in)
Parameters
Type Name Description
System.Int32 label

the label to ceil on

FST<T> fst

the fst to operate on

FST.Arc<T> follow

the arc to follow reading the label from

FST.Arc<T> arc

the arc to read into in place

FST.BytesReader in

the fst's FST.BytesReader

Returns
Type Description
FST.Arc<T>
Type Parameters
Name Description
T
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ShortestPaths<T>(FST<T>, FST.Arc<T>, T, IComparer<T>, Int32, Boolean)

Starting from node, find the top N min cost completions to a final node.

Declaration
public static Util.TopResults<T> ShortestPaths<T>(FST<T> fst, FST.Arc<T> fromNode, T startOutput, IComparer<T> comparer, int topN, bool allowEmptyString)
Parameters
Type Name Description
FST<T> fst
FST.Arc<T> fromNode
T startOutput
IComparer<T> comparer
System.Int32 topN
System.Boolean allowEmptyString
Returns
Type Description
Util.TopResults<T>
Type Parameters
Name Description
T
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ToBytesRef(Int32sRef, BytesRef)

Just converts Int32sRef to BytesRef; you must ensure the values fit into a .

Declaration
public static BytesRef ToBytesRef(Int32sRef input, BytesRef scratch)
Parameters
Type Name Description
Int32sRef input
BytesRef scratch
Returns
Type Description
BytesRef
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ToDot<T>(FST<T>, TextWriter, Boolean, Boolean)

Dumps an FST<T> to a GraphViz's dot language description for visualization. Example of use:

using (TextWriter sw = new StreamWriter("out.dot"))
{
    Util.ToDot(fst, sw, true, true);
}

and then, from command line:

dot -Tpng -o out.png out.dot

Note: larger FSTs (a few thousand nodes) won't even render, don't bother. If the FST is > 2.1 GB in size then this method will throw strange exceptions.

See also http://www.graphviz.org/.

Declaration
public static void ToDot<T>(FST<T> fst, TextWriter out, bool sameRank, bool labelStates)
Parameters
Type Name Description
FST<T> fst
TextWriter out
System.Boolean sameRank

If true, the resulting dot file will try to order states in layers of breadth-first traversal. This may mess up arcs, but makes the output FST's structure a bit clearer.
System.Boolean labelStates

If true states will have labels equal to their offsets in their binary format. Expands the graph considerably.
Type Parameters
Name Description
T
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ToInt32sRef(BytesRef, Int32sRef)

Just takes unsigned byte values from the BytesRef and converts into an Int32sRef.

NOTE: This was toIntsRef() in Lucene

Declaration
public static Int32sRef ToInt32sRef(BytesRef input, Int32sRef scratch)
Parameters
Type Name Description
BytesRef input
Int32sRef scratch
Returns
Type Description
Int32sRef
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ToUTF16(String, Int32sRef)

Just maps each UTF16 unit (char) to the s in an Int32sRef.

Declaration
public static Int32sRef ToUTF16(string s, Int32sRef scratch)
Parameters
Type Name Description
System.String s
Int32sRef scratch
Returns
Type Description
Int32sRef
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ToUTF32(Char[], Int32, Int32, Int32sRef)

Decodes the Unicode codepoints from the provided char[] and places them in the provided scratch Int32sRef, which must not be null, returning it.

Declaration
public static Int32sRef ToUTF32(char[] s, int offset, int length, Int32sRef scratch)
Parameters
Type Name Description
System.Char[] s
System.Int32 offset
System.Int32 length
Int32sRef scratch
Returns
Type Description
Int32sRef
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ToUTF32(String, Int32sRef)

Decodes the Unicode codepoints from the provided ICharSequence and places them in the provided scratch Int32sRef, which must not be null, returning it.

Declaration
public static Int32sRef ToUTF32(string s, Int32sRef scratch)
Parameters
Type Name Description
System.String s
Int32sRef scratch
Returns
Type Description
Int32sRef