/*

 * Copyright (c) 1994, 2004, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.tools.asm;

import sun.tools.java.MemberDefinition;

import java.io.OutputStream;

/**

 * A label instruction. This is a 0 size instruction.

 * It is the only valid target of a branch instruction.

 *

 * WARNING: The contents of this source file are not part of any

 * supported API.  Code that depends on them does so at its own risk:

 * they are subject to change or removal without notice.

 */

public final

class Label extends Instruction {

    static int labelCount = 0;

    int ID;

    int depth;

    MemberDefinition locals[];

    /**

     * Constructor

     */

    public Label() {

        super(0, opc_label, null);

        this.ID = ++labelCount;

    }

    /**

     * Get the final destination, eliminate jumps gotos, and jumps to

     * labels that are immediately folowed by another label. The depth

     * field is used to leave bread crumbs to avoid infinite loops.

     */

    Label getDestination() {

        Label lbl = this;

        if ((next != null) && (next != this) && (depth == 0)) {

            depth = 1;

            switch (next.opc) {

              case opc_label:

                lbl = ((Label)next).getDestination();

                break;

              case opc_goto:

                lbl = ((Label)next.value).getDestination();

                break;

              case opc_ldc:

              case opc_ldc_w:

                if (next.value instanceof Integer) {

                    Instruction inst = next.next;

                    if (inst.opc == opc_label) {

                        inst = ((Label)inst).getDestination().next;

                    }

                    if (inst.opc == opc_ifeq) {

                        if (((Integer)next.value).intValue() == 0) {

                            lbl = (Label)inst.value;

                        } else {

                            lbl = new Label();

                            lbl.next = inst.next;

                            inst.next = lbl;

                        }

                        lbl = lbl.getDestination();

                        break;

                    }

                    if (inst.opc == opc_ifne) {

                        if (((Integer)next.value).intValue() == 0) {

                            lbl = new Label();

                            lbl.next = inst.next;

                            inst.next = lbl;

                        } else {

                            lbl = (Label)inst.value;

                        }

                        lbl = lbl.getDestination();

                        break;

                    }

                }

                break;

            }

            depth = 0;

        }

        return lbl;

    }

    public String toString() {

        String s = "$" + ID + ":";

        if (value != null)

            s = s + " stack=" + value;

        return s;

    }

}