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java.lang.Object org.apache.lucene.util.fst.Util
public final class Util
Static helper methods.
Nested Class Summary | |
---|---|
static class |
Util.MinResult<T>
Holds a single input (IntsRef) + output, returned by shortestPaths() . |
static class |
Util.TopNSearcher<T>
Utility class to find top N shortest paths from start point(s). |
Method Summary | ||
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static
|
get(FST<T> fst,
BytesRef input)
Looks up the output for this input, or null if the input is not accepted |
|
static
|
get(FST<T> fst,
IntsRef input)
Looks up the output for this input, or null if the input is not accepted. |
|
static IntsRef |
getByOutput(FST<Long> fst,
long targetOutput)
Reverse lookup (lookup by output instead of by input), in the special case when your FSTs outputs are strictly ascending. |
|
static IntsRef |
getByOutput(FST<Long> fst,
long targetOutput,
FST.BytesReader in,
FST.Arc<Long> arc,
FST.Arc<Long> scratchArc,
IntsRef result)
Expert: like getByOutput(FST, long) except reusing
BytesReader, initial and scratch Arc, and result. |
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static
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readCeilArc(int label,
FST<T> fst,
FST.Arc<T> follow,
FST.Arc<T> arc,
FST.BytesReader in)
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 . |
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static
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shortestPaths(FST<T> fst,
FST.Arc<T> fromNode,
T startOutput,
Comparator<T> comparator,
int topN,
boolean allowEmptyString)
Starting from node, find the top N min cost completions to a final node. |
|
static BytesRef |
toBytesRef(IntsRef input,
BytesRef scratch)
Just converts IntsRef to BytesRef; you must ensure the int values fit into a byte. |
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static
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toDot(FST<T> fst,
Writer out,
boolean sameRank,
boolean labelStates)
Dumps an FST to a GraphViz's dot language description
for visualization. |
|
static IntsRef |
toIntsRef(BytesRef input,
IntsRef scratch)
Just takes unsigned byte values from the BytesRef and converts into an IntsRef. |
|
static IntsRef |
toUTF16(CharSequence s,
IntsRef scratch)
Just maps each UTF16 unit (char) to the ints in an IntsRef. |
|
static IntsRef |
toUTF32(char[] s,
int offset,
int length,
IntsRef scratch)
Decodes the Unicode codepoints from the provided char[] and places them in the provided scratch IntsRef, which must not be null, returning it. |
|
static IntsRef |
toUTF32(CharSequence s,
IntsRef scratch)
Decodes the Unicode codepoints from the provided CharSequence and places them in the provided scratch IntsRef, which must not be null, returning it. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Method Detail |
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public static <T> T get(FST<T> fst, IntsRef input) throws IOException
IOException
public static <T> T get(FST<T> fst, BytesRef input) throws IOException
IOException
public static IntsRef getByOutput(FST<Long> fst, long targetOutput) throws IOException
NOTE: this only works with FST<Long>
, 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.
IOException
public static IntsRef getByOutput(FST<Long> fst, long targetOutput, FST.BytesReader in, FST.Arc<Long> arc, FST.Arc<Long> scratchArc, IntsRef result) throws IOException
getByOutput(FST, long)
except reusing
BytesReader, initial and scratch Arc, and result.
IOException
public static <T> Util.MinResult<T>[] shortestPaths(FST<T> fst, FST.Arc<T> fromNode, T startOutput, Comparator<T> comparator, int topN, boolean allowEmptyString) throws IOException
IOException
public static <T> void toDot(FST<T> fst, Writer out, boolean sameRank, boolean labelStates) throws IOException
FST
to a GraphViz's dot
language description
for visualization. Example of use:
PrintWriter pw = new PrintWriter("out.dot"); Util.toDot(fst, pw, true, true); pw.close();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.
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.labelStates
- If true
states will have labels equal to their offsets in their
binary format. Expands the graph considerably.
IOException
public static IntsRef toUTF16(CharSequence s, IntsRef scratch)
public static IntsRef toUTF32(CharSequence s, IntsRef scratch)
public static IntsRef toUTF32(char[] s, int offset, int length, IntsRef scratch)
public static IntsRef toIntsRef(BytesRef input, IntsRef scratch)
public static BytesRef toBytesRef(IntsRef input, BytesRef scratch)
public static <T> FST.Arc<T> readCeilArc(int label, FST<T> fst, FST.Arc<T> follow, FST.Arc<T> arc, FST.BytesReader in) throws IOException
null
.
label
- the label to ceil onfst
- the fst to operate onfollow
- the arc to follow reading the label fromarc
- the arc to read into in placein
- the fst's FST.BytesReader
IOException
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