com.oracle.truffle.regex.tregex.parser.ast.BackReference Maven / Gradle / Ivy

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 * The Universal Permissive License (UPL), Version 1.0
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 * person obtaining a copy of this software, associated documentation and/or
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 * (a) the Software, and
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package com.oracle.truffle.regex.tregex.parser.ast;

import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
import com.oracle.truffle.regex.tregex.buffer.CompilationBuffer;
import com.oracle.truffle.regex.tregex.util.json.Json;
import com.oracle.truffle.regex.tregex.util.json.JsonValue;

/**
 * A reference to the contents of a previously matched capturing group.
 * 
 * Corresponds to the goal symbol DecimalEscape in the ECMAScript RegExp syntax.
 * 
 * Currently not implemented in TRegex and so any use of this node type causes TRegex to bail out.
 */
public class BackReference extends QuantifiableTerm {

    private final int groupNr;

    BackReference(int referencedGroupNr) {
        this.groupNr = referencedGroupNr;
    }

    private BackReference(BackReference copy) {
        super(copy);
        groupNr = copy.groupNr;
    }

    @Override
    public BackReference copy(RegexAST ast) {
        return ast.register(new BackReference(this));
    }

    @Override
    public BackReference copyRecursive(RegexAST ast, CompilationBuffer compilationBuffer) {
        return copy(ast);
    }

    /**
     * Returns the capture group number this back-reference is referring to, e.g. the referenced
     * group of {@code \1} is 1.
     */
    public int getGroupNr() {
        return groupNr;
    }

    public boolean isNestedBackReference() {
        return isFlagSet(FLAG_BACK_REFERENCE_IS_NESTED);
    }

    public void setNestedBackReference() {
        setFlag(FLAG_BACK_REFERENCE_IS_NESTED, true);
    }

    public boolean isForwardReference() {
        return isFlagSet(FLAG_BACK_REFERENCE_IS_FORWARD);
    }

    public void setForwardReference() {
        setFlag(FLAG_BACK_REFERENCE_IS_FORWARD, true);
    }

    /**
     * Returns {@code true} iff this "back-reference" is actually a reference to its own parent
     * group or a later group in the expression. In JavaScript, such nested/forward references will
     * always match the empty string.
     */
    public boolean isNestedOrForwardReference() {
        return isFlagSet(FLAG_BACK_REFERENCE_IS_NESTED | FLAG_BACK_REFERENCE_IS_FORWARD);
    }

    @Override
    public boolean isUnrollingCandidate() {
        return hasQuantifier() && getQuantifier().isUnrollTrivial();
    }

    @Override
    public boolean equalsSemantic(RegexASTNode obj, boolean ignoreQuantifier) {
        return obj instanceof BackReference && ((BackReference) obj).groupNr == groupNr && (ignoreQuantifier || quantifierEquals((BackReference) obj));
    }

    @TruffleBoundary
    @Override
    public String toString() {
        return "\\" + groupNr + quantifierToString();
    }

    @TruffleBoundary
    @Override
    public JsonValue toJson() {
        return toJson("BackReference").append(Json.prop("groupNr", groupNr));
    }
}