* Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.

import org.graalvm.compiler.bytecode.Bytecodes;

/**

 * Represents a subroutine entered via {@link Bytecodes#JSR} and exited via {@link Bytecodes#RET}.

 */

public final class JsrScope {

    /**

     * The scope outside of any JSR/RET subroutine.

     */

    private final char returnAddress;

    private final JsrScope parent;

    private JsrScope(int returnBci, JsrScope parent) {

        this.returnAddress = (char) returnBci;

        this.parent = parent;

    private JsrScope() {

        this.returnAddress = 0;

        this.parent = null;

        return returnAddress;

    /**

     * Enters a new subroutine from the current scope represented by this object.

     *

     * @param returnBci the bytecode address returned to when leaving the new scope

     * @return an object representing the newly entered scope

     */

    public JsrScope push(int returnBci) {

        if (returnBci == 0) {

            throw new IllegalArgumentException("A bytecode subroutine cannot have a return address of 0");

        if (returnBci < 1 || returnBci > 0xFFFF) {

            throw new IllegalArgumentException("Bytecode subroutine return address cannot be encoded as a char: " + returnBci);

        }

        return new JsrScope(returnBci, this);

    }

    /**

     * Determines if this is the scope outside of any JSR/RET subroutine.

     */

    public boolean isEmpty() {

        return returnAddress == 0;

    /**

     * Gets the ancestry of this scope starting with the {@link #returnAddress} of this scope's most

     * distant ancestor and ending with the {@link #returnAddress} of this object.

     *

     * @return a String where each character is a 16-bit BCI. This value can be converted to an

     *         {@code int[]} with {@code value.chars().toArray()}.

     */

    public String getAncestry() {

        StringBuilder sb = new StringBuilder();

        for (JsrScope s = this; s != null; s = s.parent) {

            if (!s.isEmpty()) {

                sb.append(s.returnAddress);

            }

        }

        return sb.reverse().toString();

    /**

     * Determines if the {@linkplain #getAncestry() ancestry} of this scope is a prefix of the

     * ancestry of {@code other}.

     */

        if (isEmpty()) {

            return true;

        }

        String ancestry = getAncestry();

        String otherAncestry = other.getAncestry();

        return otherAncestry.startsWith(ancestry);

    /**

     * Gets this scope's parent.

     *

     * @return this scope's parent or {@link #EMPTY_SCOPE} if this is the {@link #EMPTY_SCOPE}

     */

        if (isEmpty()) {

            return this;

        }

        return parent;

        int hc = returnAddress;

        JsrScope ancestor = parent;

        while (ancestor != null) {

            hc = hc ^ ancestor.returnAddress;

            ancestor = ancestor.parent;

        }

        return hc;

        if (obj != null && getClass() == obj.getClass()) {

            JsrScope ancestor = this;

            JsrScope otherAncestor = (JsrScope) obj;

            while (ancestor != null) {

                if (otherAncestor == null) {

                    return false;

                }

                if (otherAncestor.returnAddress != ancestor.returnAddress) {

                    return false;

                }

                ancestor = ancestor.parent;

                otherAncestor = otherAncestor.parent;

            }

            if (otherAncestor == null) {

                return true;

            }

        }

        return false;

        for (JsrScope ancestor = this; ancestor != null; ancestor = ancestor.parent) {

            if (!ancestor.isEmpty()) {

                if (sb.length() != 0) {

                    sb.append(", ");

                }

                sb.append((int) ancestor.returnAddress);

            }

        return "[" + sb + "]";