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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.
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package org.aspectj.apache.bcel.generic;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (https://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 */
import java.io.DataOutputStream;
import java.io.IOException;

import org.aspectj.apache.bcel.Constants;

/**
 * Abstract super class for instructions dealing with local variables.
 *
 * @version $Id: InstructionLV.java,v 1.5 2009/10/05 17:35:36 aclement Exp $
 * @author M. Dahm
 */
public class InstructionLV extends Instruction {
	protected int lvar = -1;

	public InstructionLV(short opcode, int lvar) {
		super(opcode);
		this.lvar = lvar;
	}

	public InstructionLV(short opcode) {
		super(opcode);
	}

	public void dump(DataOutputStream out) throws IOException {
		if (lvar == -1) {
			out.writeByte(opcode);
		} else {
			if (lvar < 4) {
				if (opcode == ALOAD) {
					out.writeByte(ALOAD_0 + lvar);
				} else if (opcode == ASTORE) {
					out.writeByte(ASTORE_0 + lvar);
				} else if (opcode == ILOAD) {
					out.writeByte(ILOAD_0 + lvar);
				} else if (opcode == ISTORE) {
					out.writeByte(ISTORE_0 + lvar);
				} else if (opcode == DLOAD) {
					out.writeByte(DLOAD_0 + lvar);
				} else if (opcode == DSTORE) {
					out.writeByte(DSTORE_0 + lvar);
				} else if (opcode == FLOAD) {
					out.writeByte(FLOAD_0 + lvar);
				} else if (opcode == FSTORE) {
					out.writeByte(FSTORE_0 + lvar);
				} else if (opcode == LLOAD) {
					out.writeByte(LLOAD_0 + lvar);
				} else if (opcode == LSTORE) {
					out.writeByte(LSTORE_0 + lvar);
				} else {
					if (wide()) {
						out.writeByte(Constants.WIDE);
					}
					out.writeByte(opcode);
					if (wide()) {
						out.writeShort(lvar);
					} else {
						out.writeByte(lvar);
					}
				}
			} else {
				if (wide()) {
					out.writeByte(Constants.WIDE);
				}
				out.writeByte(opcode);
				if (wide()) {
					out.writeShort(lvar);
				} else {
					out.writeByte(lvar);
				}
			}
		}
	}

	/**
	 * Long output format:
	 *
	 * 'name of opcode' "[" 'opcode number' "]" "(" 'length of instruction' ")" "<" 'local variable index' ">"
	 */
	public String toString(boolean verbose) {
		if (opcode >= Constants.ILOAD_0 && opcode <= Constants.ALOAD_3 || opcode >= Constants.ISTORE_0
				&& opcode <= Constants.ASTORE_3) {
			return super.toString(verbose);
		} else {
			return super.toString(verbose) + (lvar != -1 && lvar < 4 ? "_" : " ") + lvar;
		}
	}

	public boolean isALOAD() {
		return opcode == ALOAD || opcode >= ALOAD_0 && opcode <= ALOAD_3;
	}

	public boolean isASTORE() {
		return opcode == ASTORE || opcode >= ASTORE_0 && opcode <= ASTORE_3;
	}

	public int getBaseOpcode() {
		if (opcode >= ILOAD && opcode <= ALOAD || opcode >= ISTORE && opcode <= ASTORE) {
			// not an optimized instruction
			return opcode;
		}
		if (opcode >= Constants.ILOAD_0 && opcode <= Constants.ALOAD_3) {
			int ret = opcode - ILOAD_0;
			ret = ret - ret % 4;
			ret = ret / 4;
			return ret + ILOAD;
		}
		int ret = opcode - ISTORE_0;
		ret = ret - ret % 4;
		ret = ret / 4;
		return ret + ISTORE;
	}

	/**
	 * @return local variable index referred by this instruction.
	 */
	// optimize!
	public final int getIndex() {
		if (lvar != -1) {
			return lvar;
		}
		if (opcode >= Constants.ILOAD_0 && opcode <= Constants.ALOAD_3) {
			return (opcode - Constants.ILOAD_0) % 4;
		} else if (opcode >= Constants.ISTORE_0 && opcode <= Constants.ASTORE_3) {
			return (opcode - Constants.ISTORE_0) % 4;
		}
		return -1;
	}

	public void setIndex(int i) {
		// Switching the index for a load/store without a current index specified (ie. an aload_1 or istore_2)
		// means we need to should adjust to a normal aload/istore opcode
		if (getIndex() != i) {
			if (opcode >= Constants.ILOAD_0 && opcode <= Constants.ALOAD_3) {
				opcode = (short) (ILOAD + (opcode - ILOAD_0) / 4);
			} else if (opcode >= Constants.ISTORE_0 && opcode <= Constants.ASTORE_3) {
				opcode = (short) (ISTORE + (opcode - ISTORE_0) / 4);
			}
			this.lvar = i;
		}
	}

	public boolean canSetIndex() {
		return true;
	}

	public InstructionLV setIndexAndCopyIfNecessary(int newIndex) {
		if (canSetIndex()) {
			setIndex(newIndex);
			return this;
		} else {
			if (getIndex() == newIndex) {
				return this;
			}
			InstructionLV newInstruction = null;
			int baseOpCode = getBaseOpcode();
			if (newIndex < 4) {
				if (isStoreInstruction()) {
					newInstruction = (InstructionLV) InstructionConstants.INSTRUCTIONS[(baseOpCode - Constants.ISTORE) * 4
							+ Constants.ISTORE_0 + newIndex];
				} else {
					newInstruction = (InstructionLV) InstructionConstants.INSTRUCTIONS[(baseOpCode - Constants.ILOAD) * 4
							+ Constants.ILOAD_0 + newIndex];
				}
			} else {
				newInstruction = new InstructionLV((short) baseOpCode, newIndex);
			}
			// if (getBaseOpcode()!=newInstruction.getBaseOpcode() || newInstruction.getIndex()!=newIndex) {
			// throw new
			// RuntimeException("New Instruction created does not appear to be valid: originalBaseOpcode="+getBaseOpcode()+
			// " newBaseOpcode="+newInstruction.getBaseOpcode());
			// }
			return newInstruction;
		}
	}

	public int getLength() {
		int size = Constants.iLen[opcode];
		if (lvar == -1) {
			return size;
		} else {
			if (lvar < 4) {
				if (opcode == ALOAD || opcode == ASTORE) {
					return 1;
				} else if (opcode == ILOAD || opcode == ISTORE) {
					return 1;
				} else if (opcode == DLOAD || opcode == DSTORE) {
					return 1;
				} else if (opcode == FLOAD || opcode == FSTORE) {
					return 1;
				} else if (opcode == LLOAD || opcode == LSTORE) {
					return 1;
				} else {
					if (wide()) {
						return size + 2;
					}
					return size;
				}
			} else {
				if (wide()) {
					return size + 2;
				}
				return size;
			}
		}
	}

	private final boolean wide() {
		return lvar > Constants.MAX_BYTE;
	}

	public boolean equals(Object other) {
		if (!(other instanceof InstructionLV)) {
			return false;
		}
		InstructionLV o = (InstructionLV) other;
		return o.opcode == opcode && o.lvar == lvar;
	}

	public int hashCode() {
		return opcode * 37 + lvar;
	}

}