InsnNodeUtils.java

package net.scapeemulator.asm.util;

import org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.InsnNode;
import org.objectweb.asm.tree.IntInsnNode;
import org.objectweb.asm.tree.LdcInsnNode;

/**
 * Several utility methods related to instruction nodes.
 * @author Graham Edgecombe
 */
public final class InsnNodeUtils {

	/**
	 * Creates a numeric push instruction.
	 * @param num The number to push.
	 * @return The instruction node.
	 */
	public static AbstractInsnNode createNumericPushInsn(Number num) {
		long value = num.longValue();
		if (value == -1) {
			return new InsnNode(Opcodes.ICONST_M1);
		} else if (value == 0) {
			return new InsnNode(Opcodes.ICONST_0);
		} else if (value == 1) {
			return new InsnNode(Opcodes.ICONST_1);
		} else if (value == 2) {
			return new InsnNode(Opcodes.ICONST_2);
		} else if (value == 3) {
			return new InsnNode(Opcodes.ICONST_3);
		} else if (value == 4) {
			return new InsnNode(Opcodes.ICONST_4);
		} else if (value == 5) {
			return new InsnNode(Opcodes.ICONST_5);
		} else if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE) {
			return new IntInsnNode(Opcodes.BIPUSH, (int) value);
		} else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE) {
			return new IntInsnNode(Opcodes.SIPUSH, (int) value);
		} else if (value >= Integer.MIN_VALUE && value <= Integer.MAX_VALUE) {
			return new LdcInsnNode((int) value);
		} else {
			return new LdcInsnNode(/*(long)*/ value);
		}
	}

	/**
	 * Reads the value of a numeric push instruction (which can be an
	 * {@code ICONST_*} instruction, an {@code BIPUSH} instruction, an
	 * {@code SIPUSH} instruction or a {@code LDC_*} instruction.
	 * @param push The instruction node.
	 * @return The numeric value.
	 */
	public static long getNumericPushValue(AbstractInsnNode push) {
		if (push instanceof InsnNode) {
			switch (push.getOpcode()) {
			case Opcodes.ICONST_M1:
				return -1;
			case Opcodes.ICONST_0:
				return 0;
			case Opcodes.ICONST_1:
				return 1;
			case Opcodes.ICONST_2:
				return 2;
			case Opcodes.ICONST_3:
				return 3;
			case Opcodes.ICONST_4:
				return 4;
			case Opcodes.ICONST_5:
				return 5;
			default:
				throw new AssertionError();
			}
		} else if (push instanceof IntInsnNode) {
			return ((IntInsnNode) push).operand;
		} else {
			return ((Number) ((LdcInsnNode) push).cst).longValue();
		}
	}

	/**
	 * Finds the next non-psuedo node following the specified node.
	 * @param node The node.
	 * @return The next non-psuedo node, or {@code null} if the end of the
	 * instruction list is reached.
	 */
	public static AbstractInsnNode nextNonPsuedoNode(AbstractInsnNode node) {
		while ((node = node.getNext()) != null && node.getOpcode() == -1);
		return node;
	}

	/**
	 * Finds the previous non-psuedo node following the specified node.
	 * @param node The node.
	 * @return The previous non-psuedo node, or {@code null} if the start of
	 * the instruction list is reached.
	 */
	public static AbstractInsnNode previousNonPsuedoNode(AbstractInsnNode node) {
		while ((node = node.getPrevious()) != null && node.getOpcode() == -1);
		return node;
	}

	/**
	 * Finds the next psuedo node following the specified node.
	 * @param node The node.
	 * @return The next psuedo node, or {@code null} if the end of the
	 * instruction list is reached.
	 */
	public static AbstractInsnNode nextPsuedoNode(AbstractInsnNode node) {
		while ((node = node.getNext()) != null && node.getOpcode() != -1);
		return node;
	}
	/**
	 * Finds the previous psuedo node following the specified node.
	 * @param node The node.
	 * @return The previous psuedo node, or {@code null} if the start of the
	 * instruction list is reached.
	 */
	public static AbstractInsnNode previousPsuedoNode(AbstractInsnNode node) {
		while ((node = node.getPrevious()) != null && node.getOpcode() != -1);
		return node;
	}

	/**
	 * Default private constructor to prevent instantiation.
	 */
	private InsnNodeUtils() {
		
	}

}