Pattern2.java

/* ========================================================================
 * PlantUML : a free UML diagram generator
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 * (C) Copyright 2009-2024, Arnaud Roques
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 * Original Author:  Arnaud Roques
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package net.sourceforge.plantuml.regex;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import net.sourceforge.plantuml.Lazy;
import net.sourceforge.plantuml.jaws.Jaws;
import net.sourceforge.plantuml.teavm.TeaVM;

public class Pattern2 {

	private static final Map<String, String> QUOTED_REPLACEMENTS = new HashMap<>();
	static {
		if (TeaVM.isTeaVM())
			QUOTED_REPLACEMENTS.put("%pLN", Matcher.quoteReplacement("\\p{L}[0-9]")); // Unicode Letter or digit (TeaVM)
		else
			QUOTED_REPLACEMENTS.put("%pLN", Matcher.quoteReplacement("\\p{L}\\p{N}")); // Unicode Letter or digit
		QUOTED_REPLACEMENTS.put("%s", Matcher.quoteReplacement("\\s\u00A0")); // normal or non-breaking space
		QUOTED_REPLACEMENTS.put("%q", Matcher.quoteReplacement("'\u2018\u2019")); // single quotes
		QUOTED_REPLACEMENTS.put("%g", Matcher.quoteReplacement("\"\u201c\u201d" + Jaws.BLOCK_E1_INVISIBLE_QUOTE));
	}

	private static final Pattern TRANSFORM_PATTERN = Pattern.compile("%(pLN|s|q|g)");
	private static final Pattern2 EMPTY = new Pattern2("");

	private final String patternString;
	private final Lazy<Pattern> pattern;

	private Pattern2(String s) {
		this.patternString = s;
		this.pattern = new Lazy<>(() -> compileInternal(patternString));

	}

	public Matcher2 matcher(CharSequence input, int pos) {
		return Matcher2.build(pattern.get(), input, pos);
	}

	// A Matcher kept for find(): reset() on it costs nothing, while pattern.matcher() allocates
	// its group and state arrays every time. Command recognition asks find() of many patterns
	// for every line, almost always for a "no", so this was the first allocation site of the
	// parsing. One spare instance, borrowed with getAndSet(null): a concurrent caller finding
	// the slot empty just builds its own, and no Matcher is ever used by two threads at once.
	private final AtomicReference<Matcher> spare = new AtomicReference<>();

	public boolean find(CharSequence input) {
		Matcher m = spare.getAndSet(null);
		if (m == null)
			m = pattern.get().matcher(input);
		else
			m.reset(input);

		final boolean result = m.find();
		// Do not keep a reference to the line once done.
		m.reset("");
		spare.set(m);
		return result;
	}

	public String pattern() {
		return patternString;
	}

	public static Pattern2 cmpile(final String p) {
		if (p == null || p.length() == 0)
			return EMPTY;

		// Assert that the number of compilations for the pattern 'p' remains below the
		// threshold (5);
		// this helps detect potential excessive or unintended pattern compilations.
		// Note: using 'assert' does not impact performance in production, as assertions
		// are typically disabled by default.
		// assert COUNT.computeIfAbsent(p, k -> new AtomicInteger()).incrementAndGet() <
		// 5;

		return new Pattern2(p);

	}

	public static Pattern compileInternal(String patternString) {
		final String regex = transform(patternString);

		final Pattern result = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);
		return result;
	}

	public static String transform(String input) {
		final Matcher m = TRANSFORM_PATTERN.matcher(input);
		final StringBuffer sb = new StringBuffer(input.length());
		while (m.find()) {
			final String replacement = QUOTED_REPLACEMENTS.get(m.group());
			m.appendReplacement(sb, replacement);
		}
		m.appendTail(sb);
		return sb.toString();
	}

}