/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */

package org.apache.xalan.xsltc.compiler.util;

import org.apache.bcel.generic.Instruction;

/**
 * <p>This pseudo-instruction marks the beginning of a region of byte code that
 * can be copied into a new method, termed an "outlineable" chunk.  The size of
 * the Java stack must be the same at the start of the region as it is at the
 * end of the region, any value on the stack at the start of the region must not
 * be consumed by an instruction in the region of code, the region must not
 * contain a return instruction, no branch instruction in the region is
 * permitted to have a target that is outside the region, and no branch
 * instruction outside the region is permitted to have a target that is inside
 * the region.</p>
 * <p>The end of the region is marked by an {@link OutlineableChunkEnd}
 * pseudo-instruction.</p>
 * <p>Such a region of code may contain other outlineable regions.</p>
 */
class OutlineableChunkStart extends MarkerInstruction {
    /**
     * A constant instance of {@link OutlineableChunkStart}.  As it has no fields,
     * there should be no need to create an instance of this class. 
     */
    public static final Instruction OUTLINEABLECHUNKSTART =
                                                new OutlineableChunkStart();

    /**
     * Private default constructor.  As it has no fields,
     * there should be no need to create an instance of this class.  See
     * {@link OutlineableChunkStart#OUTLINEABLECHUNKSTART}.
     */
    private OutlineableChunkStart() {
    }

    /**
     * Get the name of this instruction.  Used for debugging.
     * @return the instruction name
     */
    public String getName() {
        return OutlineableChunkStart.class.getName();
    }

    /**
     * Get the name of this instruction.  Used for debugging.
     * @return the instruction name
     */
    public String toString() {
        return getName();
    }

    /**
     * Get the name of this instruction.  Used for debugging.
     * @return the instruction name
     */
    public String toString(boolean verbose) {
        return getName();
    }
}