package com.pan.jvm.engine;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
import com.pan.jvm.attr.CodeAttr;
import com.pan.jvm.clz.ClassFile;
import com.pan.jvm.cmd.ByteCodeCommand;
import com.pan.jvm.constant.MethodRefInfo;
import com.pan.jvm.method.Method;
public class ExecutorEngine {
private Stack<StackFrame> stack = new Stack<StackFrame>();
public ExecutorEngine() {
}
public void execute(Method mainMethod){
StackFrame mainFrame = StackFrame.create(mainMethod);
stack.push(mainFrame);
while(!stack.empty()){
StackFrame frame = stack.peek();
ExecutionResult result = frame.execute();
if(result.isPauseAndRunNewFrame()){
Method nextMethod = result.getNextMethod();
StackFrame nextFrame = StackFrame.create(nextMethod);
nextFrame.setCallerFrame(frame);
setupFunctionCallParams(frame,nextFrame);
stack.push(nextFrame);
} else {
stack.pop();
}
}
}
private void setupFunctionCallParams(StackFrame currentFrame,StackFrame nextFrame) {
Method nextMethod = nextFrame.getMethod();
List<String> paramList = nextMethod.getParameterList();
//加上1 是因为要把this也传递过去
int paramNum = paramList.size() + 1;
List<JavaObject> values = new ArrayList<JavaObject>();
//数据结构知识: 从栈中取出栈顶的x个元素
while(paramNum>0){
values.add(currentFrame.getOprandStack().pop());
paramNum --;
}
//数据结构知识: 把一个列表倒序排列
List<JavaObject> params = new ArrayList<JavaObject>();
for(int i=values.size()-1; i>=0 ;i--){
params.add(values.get(i));
}
nextFrame.setLocalVariableTable(params);
}
}