【发布时间】：2014-07-18 08:58:58
【问题描述】：
我正在尝试通过 std::map 在 C++ 中实现限价订单簿（非常简单），其中键是价格点，值是 PricePoint 对象。
Book 类有两个，bid 和 ask（分别）存储买卖。
#include <iostream>
#include <map>
#include <list>
using namespace std;
#define MAX_NUM_ORDERS 512
class Order
{
public:
unsigned int id;
unsigned int price;
unsigned int volume;
bool side;
time_t added;
time_t executed;
time_t cancelled;
Order *next;
Order *prev;
Order(unsigned int price, unsigned int volume, bool side)
{
this->id = 0;
this->price = price;
this->volume = volume;
this->side = side;
this->added = 0;
this->executed = 0;
this->cancelled = 0;
this->next = 0;
this->prev = 0;
}
};
class PricePoint
{
public:
Order *head;
Order *tail;
PricePoint(void)
{
this->head = 0;
this->tail = 0;
}
void insertAfter(Order *node, Order new_node)
{
new_node.next = node->next;
if(node->next == 0)
{
this->tail = &new_node;
}
else
{
node->next->prev = &new_node;
}
node->next = &new_node;
}
void insertHead(Order new_node)
{
if(this->head == 0)
{
this->head = &new_node;
this->tail = &new_node;
new_node.prev = 0;
new_node.next = 0;
}
else
{
insertAfter(this->tail, new_node);
}
}
void insertTail(Order new_node)
{
if (this->tail == 0)
{
insertHead(new_node);
}
else
{
insertAfter(this->tail, new_node);
}
}
unsigned int count(void)
{
unsigned int i;
Order node(0, 0, false);
while(node.next == 0)
{
for(i=0;i<=MAX_NUM_ORDERS;i++)
{
// lol
}
}
return i;
}
bool empty(void)
{
if(this->head == 0)
{
return true;
}
else
{
return false;
}
}
void print(void)
{
if(this->empty() == true)
{
cout<<"[None]"<<endl;
return;
}
else
{
if(this->head != 0)
{
unsigned int i;
Order *node = this->head; // start at the head
cout<<"id, volume, added"<<endl; // labels
while(node->next != 0) // while we're not at the end
{
cout<<node->id<<", "<<node->volume<<", "<<node->added<<endl;
node = node->next;
}
}
else // try and catch it again i guess?
{
cout<<"[None]"<<endl;
return;
}
}
}
};
class Book
{
public:
map<int, PricePoint> bid; // buy-side
map<int, PricePoint> ask; // sell-side
int add(Order order)
{
order.id = this->bid.size() + this->ask.size() + 1; // this way, buy-side and sell-side orders have unique identifiers
if(order.side == false) // buy order
{
if(this->bid.count(order.price) == 0) // if the price point isn't already there
{
PricePoint pp;
pair<int, PricePoint> new_pp(order.price, pp);
bid.insert(new_pp); // add the price point (i.e. add an entry to the map)
}
else
{
this->bid[order.price].insertTail(order); // insert at tail of the doubly linked list
}
}
else if(order.side == true) // sell order
{
if(this->bid.count(order.price) == 0)
{
PricePoint pp;
pair<int, PricePoint> new_pp(order.price, pp);
ask.insert(new_pp); // add the price point (i.e. add an entry to the map)
}
{
this->ask[order.price].insertTail(order); // insert at the tail of the doubly linked list
}
}
return order.id; // the order's id
}
int cancel(unsigned int id)
{
}
void print(void)
{
unsigned int i = 0;
cout<<"-------------------------------------BIDS--------------------------------------"<<endl;
cout<<this->bid.size()<<endl;
for(i=0;i<this->bid.size();i++)
{
cout<<"Orders for $"<<i<<":"<<endl;
this->bid[i].print();
}
i = 0;
cout<<endl;
cout<<"-------------------------------------ASKS--------------------------------------"<<endl;
for(i=0;i<this->ask.size();i++)
{
cout<<"Orders for $"<<i<<":"<<endl;
this->ask[i].print();
}
cout<<endl;
}
};
int main(void)
{
unsigned int i;
Book orderbook; // our limit order book
// some orders
Order a(4, 33, false);
Order b(4, 12, true);
Order c(5, 33, true);
//add them
orderbook.add(a);
orderbook.add(b);
orderbook.add(c);
cout<<"Order book is as follows:"<<endl;
orderbook.print();
system("pause");
return 0;
}
我想打印订单簿，但是当我尝试遍历列表时遇到未处理的异常，如下所示：
Unhandled exception at 0x00a418aa in orderbook.exe: 0xC0000005: Access violation reading location 0x00000039.
在调试器中，我看到next 指针最终变成了垃圾，这表明我未能正确初始化，是吗？
此外，程序在异常之前输出垃圾数据（也表示未初始化的指针）。
非常感谢任何帮助，非常感谢。
【问题讨论】：
-
您的函数将
Order作为一个值，然后您执行this->tail = &new_node;之类的操作，这会导致tail指向函数返回时不再存在的某个位置。将其作为参考传递。 -
这是方式的许多代码，请将其缩小到相关位。如何找出哪些部分是相关的？在调试器中运行程序，它会停在异常的位置，这意味着你会知道问题出在哪里，并且应该能够找出相关的部分。
-
你为什么不用
std::list？你包括它：#include <list>但你不使用它。std::list是标准的 C++ 链表类，那么你为什么要重新发明轮子呢？你已经在使用std::map，那你为什么不使用std::list？？