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package com.oracle.truffle.regex.literal;
import com.oracle.truffle.regex.RegexLanguage;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.EmptyEndsWith;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.EmptyEquals;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.EmptyIndexOf;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.EmptyStartsWith;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.EndsWith;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.Equals;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.IndexOfString;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.RegionMatches;
import com.oracle.truffle.regex.literal.LiteralRegexExecRootNode.StartsWith;
import com.oracle.truffle.regex.tregex.parser.RegexProperties;
import com.oracle.truffle.regex.tregex.parser.ast.RegexAST;
import com.oracle.truffle.regex.tregex.parser.ast.visitors.PreCalcResultVisitor;
import com.oracle.truffle.regex.tregex.string.Encodings;
This regex engine is designed for very simple cases, where the regular expression can be directly translated to common string operations. It will map expressions to simple index checks ( EmptyStartsWith, EmptyEndsWith, EmptyIndexOf) or to the following methods of String (or equivalent nodes in input) whenever possible:
/**
* This regex engine is designed for very simple cases, where the regular expression can be directly
* translated to common string operations. It will map expressions to simple index checks (
* {@link EmptyStartsWith}, {@link EmptyEndsWith}, {@link EmptyIndexOf}) or to the following methods
* of {@link String} (or equivalent nodes in {@link com.oracle.truffle.regex.tregex.nodes.input})
* whenever possible:
* <ul>
* <li>{@link String#isEmpty()}: {@link EmptyEquals}</li>
* <li>{@link String#indexOf(String)}: {@link IndexOfString}</li>
* <li>{@link String#startsWith(String)}: {@link StartsWith}</li>
* <li>{@link String#endsWith(String)}: {@link EndsWith}</li>
* <li>{@link String#equals(Object)}: {@link Equals}</li>
* <li>{@link String#regionMatches(int, String, int, int)}: {@link RegionMatches}</li>
* </ul>
*/
public final class LiteralRegexEngine {
public static LiteralRegexExecRootNode createNode(RegexLanguage language, RegexAST ast) {
/*
* Bail out if the search string would be huge. This can occur with expressions like
* /a{1000000}/.
*/
RegexProperties props = ast.getProperties();
if (ast.isLiteralString() && props.isFixedCodePointWidth() && (ast.getEncoding() == Encodings.UTF_16_RAW || !props.hasLoneSurrogates()) &&
(!props.hasQuantifiers() || ast.getRoot().getMinPath() <= Short.MAX_VALUE)) {
return createLiteralNode(language, ast);
} else {
return null;
}
}
private static LiteralRegexExecRootNode createLiteralNode(RegexLanguage language, RegexAST ast) {
PreCalcResultVisitor preCalcResultVisitor = PreCalcResultVisitor.run(ast, true);
boolean caret = ast.getRoot().startsWithCaret();
boolean dollar = ast.getRoot().endsWithDollar();
if (ast.getRoot().getMinPath() == 0) {
if (caret) {
if (dollar) {
return new EmptyEquals(language, ast, preCalcResultVisitor);
}
return new EmptyStartsWith(language, ast, preCalcResultVisitor);
}
if (dollar) {
return new EmptyEndsWith(language, ast, preCalcResultVisitor);
}
return new EmptyIndexOf(language, ast, preCalcResultVisitor);
}
if (caret) {
if (dollar) {
return new Equals(language, ast, preCalcResultVisitor);
}
return new StartsWith(language, ast, preCalcResultVisitor);
}
if (dollar) {
return new EndsWith(language, ast, preCalcResultVisitor);
}
if (ast.getFlags().isSticky()) {
return new RegionMatches(language, ast, preCalcResultVisitor);
}
if (preCalcResultVisitor.getLiteral().encodedLength() <= 64) {
return new IndexOfString(language, ast, preCalcResultVisitor);
}
return null;
}
}