/*
 * Copyright  2000-2004 The Apache Software Foundation
 *
 *  Licensed 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. 
 *
 */
package org.apache.bcel.generic;

import java.io.DataOutputStream;
import java.io.IOException;
import org.apache.bcel.util.ByteSequence;

/**
 * LDC - Push item from constant pool.
 * 
 * <PRE>
 * Stack: ... -&gt; ..., item
 * </PRE>
 * 
 * @version $Id: LDC.java 386056 2006-03-15 11:31:56Z tcurdt $
 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 */
public class LDC extends CPInstruction implements PushInstruction,
		ExceptionThrower, TypedInstruction {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * Empty constructor needed for the Class.newInstance() statement in
	 * Instruction.readInstruction(). Not to be used otherwise.
	 */
	LDC() {
	}

	public LDC(int index) {
		super(org.apache.bcel.Constants.LDC_W, index);
		setSize();
	}

	// Adjust to proper size
	protected final void setSize() {
		if (index <= org.apache.bcel.Constants.MAX_BYTE) { // Fits in one byte?
			opcode = org.apache.bcel.Constants.LDC;
			length = 2;
		} else {
			opcode = org.apache.bcel.Constants.LDC_W;
			length = 3;
		}
	}

	/**
	 * Dump instruction as byte code to stream out.
	 * 
	 * @param out
	 *            Output stream
	 */
	@Override
	public void dump(DataOutputStream out) throws IOException {
		out.writeByte(opcode);
		if (length == 2) {
			out.writeByte(index);
		} else {
			out.writeShort(index);
		}
	}

	/**
	 * Set the index to constant pool and adjust size.
	 */
	@Override
	public final void setIndex(int index) {
		super.setIndex(index);
		setSize();
	}

	/**
	 * Read needed data (e.g. index) from file.
	 */
	@Override
	protected void initFromFile(ByteSequence bytes, boolean wide)
			throws IOException {
		length = 2;
		index = bytes.readUnsignedByte();
	}

	public Object getValue(ConstantPoolGen cpg) {
		org.apache.bcel.classfile.Constant c = cpg.getConstantPool()
				.getConstant(index);
		switch (c.getTag()) {
		case org.apache.bcel.Constants.CONSTANT_String:
			int i = ((org.apache.bcel.classfile.ConstantString) c)
					.getStringIndex();
			c = cpg.getConstantPool().getConstant(i);
			return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes();
		case org.apache.bcel.Constants.CONSTANT_Float:
			return new Float(
					((org.apache.bcel.classfile.ConstantFloat) c).getBytes());
		case org.apache.bcel.Constants.CONSTANT_Integer:
			return new Integer(
					((org.apache.bcel.classfile.ConstantInteger) c).getBytes());
		case org.apache.bcel.Constants.CONSTANT_Class:
			return c;
		default: // Never reached
			throw new RuntimeException("Unknown or invalid constant type at "
					+ index);
		}
	}

	@Override
	public Type getType(ConstantPoolGen cpg) {
		switch (cpg.getConstantPool().getConstant(index).getTag()) {
		case org.apache.bcel.Constants.CONSTANT_String:
			return Type.STRING;
		case org.apache.bcel.Constants.CONSTANT_Float:
			return Type.FLOAT;
		case org.apache.bcel.Constants.CONSTANT_Integer:
			return Type.INT;
		case org.apache.bcel.Constants.CONSTANT_Class:
			return Type.CLASS;
		default: // Never reached
			throw new RuntimeException("Unknown or invalid constant type at "
					+ index);
		}
	}

	@Override
	public Class<?>[] getExceptions() {
		return org.apache.bcel.ExceptionConstants.EXCS_STRING_RESOLUTION;
	}

	/**
	 * Call corresponding visitor method(s). The order is: Call visitor methods
	 * of implemented interfaces first, then call methods according to the class
	 * hierarchy in descending order, i.e., the most specific visitXXX() call
	 * comes last.
	 * 
	 * @param v
	 *            Visitor object
	 */
	@Override
	public void accept(Visitor v) {
		v.visitStackProducer(this);
		v.visitPushInstruction(this);
		v.visitExceptionThrower(this);
		v.visitTypedInstruction(this);
		v.visitCPInstruction(this);
		v.visitLDC(this);
	}
}
