/* Software Name : AsmDex
 * Version : 1.0
 *
 * Copyright © 2012 France Télécom
 * 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. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS 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 COPYRIGHT OWNER OR 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.
 */

package org.ow2.asmdex.instruction;

import java.util.LinkedList;

import org.ow2.asmdex.lowLevelUtils.ByteVector;
import org.ow2.asmdex.lowLevelUtils.IDalvikValueReader;
import org.ow2.asmdex.structureCommon.Label;
import org.ow2.asmdex.structureWriter.ConstantPool;

/**
 * Encodes and decodes an instruction built with the Dalvik format 10T.
 * 
 * @author Julien Névo
 */
public class InstructionFormat10T extends Instruction implements IOffsetInstruction {

	private static final int INSTRUCTION_SIZE = 2; // Instruction size in bytes.
	
	/**
	 * Offset to the pointed Instruction.
	 */
	private int offset;
	
	/**
	 * Offset in bytes of the instruction from the beginning of the method.
	 */
	private int instructionOffset;
	
	/**
	 * Returns the offset pointing to the beginning of the branch, from the start of the Dex file.
	 * @return the offset pointing to the beginning of the branch, from the start of the Dex file.
	 */
	@Override
	public int getOffset() { return offset; }
	
	/**
	 * Label to which to jump.
	 */
	private Label label;
	
	/**
	 * Returns the label to which the instruction jumps.
	 * @return the label to which the instruction jumps.
	 */
	@Override
	public Label getLabel() { return label; }
	
	/**
	 * Constructor of the Instruction, using a Reader to parse its bytecode.
	 * @param reader reader on the Instruction to parse, pointing after the 16-bit opcode.
	 * @param opcode 16-bit opcode.
	 */
//	public InstructionFormat10T(IDalvikValueReader reader, int opcode) {
//		super(opcode);
//		
//		// The format is AA|op.
//		int readOffset = ((byte)(opcodeHighOrderByte & 0xff)) * 2; // * 2 because branch offsets are word based.
//		// Offset points to the beginning of the branch, from the start of the Dex file.
//		// It is related to the current opcode (hence the -2).
//		offset = reader.getPos() - 2 + readOffset;
//	}
	
	/**
	 * Returns the Offset encoded in the given 16-bit opcode. <i>It must be performed only once after
	 * having read the opcode.</i>
	 * @param reader reader on the Instruction to parse, pointing after the 16-bit opcode.
	 * @param opcode the 16-bit opcode.
	 * @return the Offset from the beginning of the Dex file.
	 */
	public static int getOffset(IDalvikValueReader reader, int opcode) {
		// The format is AA|op.
		int readOffset = ((byte)((opcode >> 8) & 0xff)) * 2; // * 2 because branch offsets are word based.
		// Offset points to the beginning of the branch, from the start of the Dex file.
		// It is related to the current opcode (hence the -2).
		return reader.getPos() - 2 + readOffset;
	}
	

	
	/**
	 * Constructor of the Instruction by providing all the elements it's composed of.
	 * @param opcode 8 or 16 bits opcode.
	 * @param label Label to which is linked this Instruction.
	 * @param instructionOffset offset of this Instruction from the beginning of its Method.
	 */
	public InstructionFormat10T(int opcode, Label label, int instructionOffset) {
		super(opcode);
		
		this.label = label;
		this.instructionOffset = instructionOffset;
	}
	
	protected static final LinkedList<InstructionFormat10T> instances = new LinkedList<InstructionFormat10T>();
	public static final InstructionFormat10T obtain(int opcode, Label label, int instructionOffset)
	{
		InstructionFormat10T instruction = instances.poll();
		if (instruction == null)
		{
			return new InstructionFormat10T(opcode, label, instructionOffset);
		}
		
		instruction.opcodeHighOrderByte = (opcode >> 8) & 0xff;
		instruction.opcodeByte = opcode & 0xff;
		
		instruction.label = label;
		instruction.instructionOffset = instructionOffset;
		
		return instruction;
	}
	
	public void recycle(Instruction instruction)
	{
		instances.add((InstructionFormat10T)instruction);
	}
	
	@Override
	public int getSize() {
		return INSTRUCTION_SIZE;
	}
	
//	@Override
//	public int getNbEncodedRegisters() {
//		return 0;
//	}
	
//	@Override
//	public int[] getUsedRegisters() {
//		return null;
//	}
	
	@Override
	public int getInstructionOffset() {
		return instructionOffset;
	}
	
	@Override
	public void setInstructionOffset(int instructionOffset) {
		this.instructionOffset = instructionOffset;
	};
	
	@Override
	public void write(ByteVector out, ConstantPool constantPool) {
		// The format is AA|op.
		int firstShort = ((((label.getOffset() - instructionOffset) / 2)
				& 0xff) << 8) + opcodeByte; // / 2 because offsets are word-based.
		out.putShort(firstShort);
	}
}