CapabilitiesHookInjector.java

package openmods.stencil;

import com.google.common.base.Throwables;
import openmods.Log;
import openmods.api.IResultListener;
import openmods.asm.MethodMatcher;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.commons.Method;

public class CapabilitiesHookInjector extends ClassVisitor {

	private final Type hookType;

	private final Method hookMethod;

	private final MethodMatcher targetMethod;

	private final IResultListener listener;

	private class MethodInjector extends MethodVisitor {

		public MethodInjector(MethodVisitor mv) {
			super(Opcodes.ASM5, mv);
		}

		@Override
		public void visitInsn(int opcode) {
			if (opcode == Opcodes.RETURN) {
				Log.debug("Injecting call into OpenGLHelper.init()");
				super.visitMethodInsn(Opcodes.INVOKESTATIC, hookType.getInternalName(), hookMethod.getName(), hookMethod.getDescriptor(), false);
				listener.onSuccess();
			}

			super.visitInsn(opcode);
		}
	}

	@Override
	public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
		MethodVisitor parent = super.visitMethod(access, name, desc, signature, exceptions);
		return targetMethod.match(name, desc)? new MethodInjector(parent) : parent;
	}

	public CapabilitiesHookInjector(String rawCls, ClassVisitor cv, IResultListener listener) {
		super(Opcodes.ASM5, cv);

		this.listener = listener;

		Type type = Type.getMethodType(Type.VOID_TYPE);
		this.targetMethod = new MethodMatcher(rawCls.replace('.', '/'), type.getDescriptor(), "initializeTextures", "func_77474_a");

		this.hookType = Type.getType(FramebufferHooks.class);

		try {
			this.hookMethod = Method.getMethod(FramebufferHooks.class.getMethod("init"));
		} catch (Throwable t) {
			throw Throwables.propagate(t);
		}
	}

}