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package ftbsc.lll.utils;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.*;
import java.util.Comparator;
/**
* Various methods for manipulating the stack.
* Includes anything from instantiation to variable manipulation - just about
* anything that loads stuff on or from the stack.
*/
public class StackUtils implements Opcodes {
/**
* Creates a new instance of an object, given its internal name, constructor descriptor and instructions to load
* the parameters.
* The created object is loaded on the stack.
* @param name the internal name of the object to initialize, where
* the internal name of a class is its fully qualified name, where '.' are replaced by '/'
* @param desc the descriptor of the constructor to call
* @param args nodes containing instructions to load the constructor arguments, in the right order
* @return an instruction list containing the opcodes needed to create the new object and load it on the stack.
*/
public static InsnList instantiate(String name, String desc, AbstractInsnNode... args) {
InsnSequence is = new InsnSequence();
is.add(args);
return instantiate(name, desc, is);
}
/**
* Creates a new instance of an object, given its internal name, constructor descriptor and instructions to load
* the parameters.
* The created object is loaded on the stack.
* @param name the internal name of the object to initialize, where
* the internal name of a class is its fully qualified name, where '.' are replaced by '/'
* @param desc the descriptor of the constructor to call
* @param args a list of instructions loading the constructor arguments onto the stack in the correct order
* @return an instruction list containing the opcodes needed to create the new object and load it on the stack.
*/
public static InsnList instantiate(String name, String desc, InsnList args) {
InsnSequence list = new InsnSequence();
list.add(new TypeInsnNode(NEW, name), new InsnNode(DUP));
if(args != null) list.add(args);
list.add(new MethodInsnNode(INVOKESPECIAL, name, "<init>", desc, false));
return list;
}
/**
* Creates a new local variable, lasting in scope from the first to the last label of the given method.
* @param method the method for which to declare the local variable
* @param name the variable's name
* @param desc the type descriptor for the new variable
* @return the index value of the new local variable
*/
public static int addLocalVariable(MethodNode method, String name, String desc) {
return addLocalVariable(
method, name, desc,
(LabelNode) PatternMatcher.builder().label().build().find(method).getFirst(),
(LabelNode) PatternMatcher.builder().label().reverse().build().find(method).getFirst()
);
}
/**
* Creates a new local variable, lasting in scope between two given {@link LabelNode}s.
* @param method the method for which to declare the local variable
* @param name the variable's name
* @param desc the type descriptor for the new variable
* @param start the label at which the variable should enter scope
* @param end the label at which the variable should go out of scope
* @return the index value of the new local variable
*/
public static int addLocalVariable(MethodNode method, String name, String desc, LabelNode start, LabelNode end) {
final int targetIndex = findFirstFreeIndex(method);
LocalVariableNode variable = new LocalVariableNode(name, desc, null, start, end, targetIndex);
method.localVariables.add(variable);
return targetIndex;
}
/**
* Finds the first free index in the given {@link MethodNode}.
* Used to create variables.
* @param method the method to look in
* @return the found index
*/
public static int findFirstFreeIndex(MethodNode method) {
return method.localVariables
.stream()
.max(Comparator.comparingInt(v -> v.index))
.map(var -> var.desc.equals("J") || var.desc.equals("D")
? var.index + 2 //skip two if long or double - major java moment
: var.index + 1)
.orElse(0);
}
}
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zaaarf