Add method for deleting MethodNode arguments

asm/src/main/java/dev/openrs2/asm/MethodNodeUtils.java

@@ -0,0 +1,135 @@
+package dev.openrs2.asm;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.Type;
+import org.objectweb.asm.tree.AbstractInsnNode;
+import org.objectweb.asm.tree.AnnotationNode;
+import org.objectweb.asm.tree.FrameNode;
+import org.objectweb.asm.tree.IincInsnNode;
+import org.objectweb.asm.tree.MethodNode;
+import org.objectweb.asm.tree.VarInsnNode;
+
+public final class MethodNodeUtils {
+	private static int localIndex(int access, List<Type> argTypes, int argIndex) {
+		var localIndex = 0;
+		if ((access & Opcodes.ACC_STATIC) == 0) {
+			localIndex++;
+		}
+		for (int i = 0; i < argIndex; i++) {
+			localIndex += argTypes.get(i).getSize();
+		}
+		return localIndex;
+	}
+
+	private static int remap(int i, Type argType, int localIndex) {
+		if (i >= localIndex) {
+			return i - argType.getSize();
+		}
+		return i;
+	}
+
+	private static List<Integer> remapAll(List<Integer> indexes, Type argType, int localIndex) {
+		return indexes.stream()
+			.map(i -> remap(i, argType, localIndex))
+			.collect(Collectors.toList());
+	}
+
+	public static void deleteArgument(MethodNode method, int argIndex) {
+		/* remove argument from the signature */
+		var type = Type.getType(method.desc);
+
+		var argTypes = new ArrayList<>(Arrays.asList(type.getArgumentTypes()));
+		var argType = argTypes.remove(argIndex);
+
+		method.desc = Type.getMethodDescriptor(type.getReturnType(), argTypes.toArray(Type[]::new));
+
+		if (method.signature != null) {
+			throw new UnsupportedOperationException("Signatures unsupported");
+		}
+
+		/* calculate index of the local we're removing */
+		var localIndex = localIndex(method.access, argTypes, argIndex);
+
+		/* remove ParameterNode */
+		if (method.parameters != null) {
+			method.parameters.remove(argIndex);
+		}
+
+		/* remove annotations */
+		if (method.visibleAnnotableParameterCount != 0) {
+			throw new UnsupportedOperationException("Non-zero visibleAnnotableParameterCount unsupported");
+		}
+
+		if (method.visibleParameterAnnotations != null) {
+			@SuppressWarnings("unchecked")
+			var annotations = (List<AnnotationNode>[]) new List<?>[method.visibleParameterAnnotations.length - 1];
+			System.arraycopy(method.visibleParameterAnnotations, 0, annotations, 0, argIndex);
+			System.arraycopy(method.visibleParameterAnnotations, argIndex + 1, annotations, argIndex, method.visibleParameterAnnotations.length - argIndex - 1);
+			method.visibleParameterAnnotations = annotations;
+		}
+
+		if (method.invisibleAnnotableParameterCount != 0) {
+			throw new UnsupportedOperationException("Non-zero invisibleAnnotableParameterCount unsupported");
+		}
+
+		if (method.invisibleParameterAnnotations != null) {
+			@SuppressWarnings("unchecked")
+			var annotations = (List<AnnotationNode>[]) new List<?>[method.invisibleParameterAnnotations.length - 1];
+			System.arraycopy(method.invisibleParameterAnnotations, 0, annotations, 0, argIndex);
+			System.arraycopy(method.invisibleParameterAnnotations, argIndex + 1, annotations, argIndex, method.invisibleParameterAnnotations.length - argIndex - 1);
+			method.invisibleParameterAnnotations = annotations;
+		}
+
+		/* reduce maxLocals */
+		method.maxLocals -= argType.getSize();
+
+		/* remap locals */
+		if (method.localVariables != null) {
+			method.localVariables.removeIf(v -> v.index == localIndex);
+			method.localVariables.forEach(v -> v.index = remap(v.index, argType, localIndex));
+		}
+
+		if (method.visibleLocalVariableAnnotations != null) {
+			method.visibleLocalVariableAnnotations.removeIf(v -> v.index.contains(localIndex));
+			method.visibleLocalVariableAnnotations.forEach(v -> v.index = remapAll(v.index, argType, localIndex));
+		}
+
+		if (method.invisibleLocalVariableAnnotations != null) {
+			method.invisibleLocalVariableAnnotations.removeIf(v -> v.index.contains(localIndex));
+			method.invisibleLocalVariableAnnotations.forEach(v -> v.index = remapAll(v.index, argType, localIndex));
+		}
+
+		for (var it = method.instructions.iterator(); it.hasNext(); ) {
+			var insn = it.next();
+			switch (insn.getType()) {
+			case AbstractInsnNode.VAR_INSN:
+				var varInsn = (VarInsnNode) insn;
+				varInsn.var = remap(varInsn.var, argType, localIndex);
+				break;
+			case AbstractInsnNode.IINC_INSN:
+				var iincInsn = (IincInsnNode) insn;
+				iincInsn.var = remap(iincInsn.var, argType, localIndex);
+				break;
+			case AbstractInsnNode.FRAME:
+				var frame = (FrameNode) insn;
+				if (frame.type != Opcodes.F_NEW) {
+					throw new UnsupportedOperationException("Only F_NEW frames are supported");
+				}
+
+				for (int i = 0; i < argType.getSize(); i++) {
+					frame.local.remove(localIndex);
+				}
+				break;
+			}
+		}
+	}
+
+	private MethodNodeUtils() {
+		/* empty */
+	}
+}