mirror of https://github.com/DanilaFe/abacus
99 lines
3.3 KiB
Java
99 lines
3.3 KiB
Java
package org.nwapw.abacus.lexing;
|
|
|
|
import org.nwapw.abacus.lexing.pattern.EndNode;
|
|
import org.nwapw.abacus.lexing.pattern.Match;
|
|
import org.nwapw.abacus.lexing.pattern.Pattern;
|
|
import org.nwapw.abacus.lexing.pattern.PatternNode;
|
|
|
|
import java.util.ArrayList;
|
|
import java.util.Comparator;
|
|
import java.util.HashSet;
|
|
|
|
/**
|
|
* A lexer that can generate tokens of a given type given a list of regular expressions
|
|
* to operate on.
|
|
* @param <T> the type used to identify which match belongs to which pattern.
|
|
*/
|
|
public class Lexer<T> {
|
|
|
|
/**
|
|
* The registered patterns.
|
|
*/
|
|
private ArrayList<Pattern<T>> patterns;
|
|
|
|
/**
|
|
* Creates a new lexer with no registered patterns.
|
|
*/
|
|
public Lexer(){
|
|
patterns = new ArrayList<>();
|
|
}
|
|
|
|
/**
|
|
* Registers a single pattern.
|
|
* @param pattern the pattern regex
|
|
* @param id the ID by which to identify the pattern.
|
|
*/
|
|
public void register(String pattern, T id){
|
|
Pattern<T> compiledPattern = new Pattern<>(pattern, id);
|
|
if(compiledPattern.getHead() != null) patterns.add(compiledPattern);
|
|
}
|
|
|
|
/**
|
|
* Reads one token from the given string.
|
|
* @param from the string to read from
|
|
* @param startAt the index to start at
|
|
* @param compare the comparator used to sort tokens by their ID.
|
|
* @return the best match.
|
|
*/
|
|
public Match<T> lexOne(String from, int startAt, Comparator<T> compare){
|
|
ArrayList<Match<T>> matches = new ArrayList<>();
|
|
HashSet<PatternNode<T>> currentSet = new HashSet<>();
|
|
HashSet<PatternNode<T>> futureSet = new HashSet<>();
|
|
int index = startAt;
|
|
for(Pattern<T> pattern : patterns){
|
|
pattern.getHead().addInto(currentSet);
|
|
}
|
|
while(!currentSet.isEmpty()){
|
|
for(PatternNode<T> node : currentSet){
|
|
if(index < from.length() && node.matches(from.charAt(index))) {
|
|
node.addOutputsInto(futureSet);
|
|
} else if(node instanceof EndNode){
|
|
matches.add(new Match<>(startAt, index, ((EndNode<T>) node).getPatternId()));
|
|
}
|
|
}
|
|
|
|
HashSet<PatternNode<T>> tmp = currentSet;
|
|
currentSet = futureSet;
|
|
futureSet = tmp;
|
|
futureSet.clear();
|
|
|
|
index++;
|
|
}
|
|
matches.sort((a, b) -> compare.compare(a.getType(), b.getType()));
|
|
if(compare != null) {
|
|
matches.sort(Comparator.comparingInt(a -> a.getTo() - a.getFrom()));
|
|
}
|
|
return matches.isEmpty() ? null : matches.get(matches.size() - 1);
|
|
}
|
|
|
|
/**
|
|
* Reads all tokens from a string.
|
|
* @param from the string to start from.
|
|
* @param startAt the index to start at.
|
|
* @param compare the comparator used to sort matches by their IDs.
|
|
* @return the resulting list of matches, in order, or null on error.
|
|
*/
|
|
public ArrayList<Match<T>> lexAll(String from, int startAt, Comparator<T> compare){
|
|
int index = startAt;
|
|
ArrayList<Match<T>> matches = new ArrayList<>();
|
|
Match<T> lastMatch = null;
|
|
while((lastMatch = lexOne(from, index, compare)) != null && index < from.length()){
|
|
if(lastMatch.getTo() == lastMatch.getFrom()) return null;
|
|
matches.add(lastMatch);
|
|
index += lastMatch.getTo() - lastMatch.getFrom();
|
|
}
|
|
return matches;
|
|
}
|
|
|
|
}
|