package me.lzb.jvm.cmd;
import me.lzb.jvm.clz.ClassFile;
import me.lzb.jvm.constant.MethodRefInfo;
import me.lzb.jvm.engine.ExecutionResult;
import me.lzb.jvm.engine.JavaObject;
import me.lzb.jvm.engine.MethodArea;
import me.lzb.jvm.engine.StackFrame;
import me.lzb.jvm.method.Method;
import me.lzb.jvm.print.ExecutionVisitor;
public class InvokeVirtualCmd extends TwoOperandCmd {
public InvokeVirtualCmd(ClassFile clzFile, String opCode) {
super(clzFile, opCode);
}
public String toString() {
return super.getOperandAsMethod();
}
@Override
public void execute(StackFrame frame, ExecutionResult result) {
//先得到对该方法的描述
MethodRefInfo methodRefInfo = (MethodRefInfo) this.getConstantInfo(this.getIndex());
String className = methodRefInfo.getClassName();
String methodName = methodRefInfo.getMethodName();
// 我们没有实现System.out.println方法, 所以也不用建立新的栈帧, 直接调用Java的方法, 打印出来即可。
if (isSystemOutPrintlnMethod(className, methodName)) {
JavaObject jo = (JavaObject) frame.getOprandStack().pop();
String value = jo.toString();
System.out.println("-------------------" + value + "----------------");
// 这里就是那个out对象, 因为是个假的,直接pop出来
frame.getOprandStack().pop();
return;
}
//注意:多态, 这才是真正的对象, 先从该对象的class 中去找对应的方法,找不到的话再去找父类的方法
JavaObject jo = frame.getOprandStack().peek();
MethodArea ma = MethodArea.getInstance();
Method m = null;
String currentClassName = jo.getClassName();
while (currentClassName != null) {
ClassFile currentClassFile = ma.findClassFile(currentClassName);
m = currentClassFile.getMethod(methodRefInfo.getMethodName(),
methodRefInfo.getParamAndReturnType());
if (m != null) {
break;
} else {
//查找父类
currentClassName = currentClassFile.getSuperClassName();
}
}
if (m == null) {
throw new RuntimeException("Can't find method for :" + methodRefInfo.toString());
}
result.setNextAction(ExecutionResult.PAUSE_AND_RUN_NEW_FRAME);
result.setNextMethod(m);
}
@Override
public void printExecute(ExecutionVisitor visitor) {
visitor.visitInvokeVirtualCmd(this);
}
private boolean isSystemOutPrintlnMethod(String className, String methodName) {
return "java/io/PrintStream".equals(className)
&& "println".equals(methodName);
}
}