简单Trace类实现

　　《C++沉思录》27章内容修改后所得：
 1 /************************************************************************/
 2 /* Trace类，以及trace类输出重定向，C++沉思录27章                  */
 3 /************************************************************************/
 4 #pragma once
 5 #include <iostream>
 6 using namespace std;
 7 
 8 //打开/关闭trace输入输出流
 9 static const int trace_debug = 1;
10 
11 //输出流
12 class Channel
13 {
14 public:
15     Channel (ostream* o = &std::cout): trace_file(o){}
16     //重定向输出流
17     void Reset(ostream* o = &std::cout)
18     {
19         trace_file = o;
20     }
21 private:
22     friend class Trace;
23     template<class T> friend class Obj_trace;
24     ostream* trace_file;
25 };
26 typedef CSingleton<Channel> TraceChannel;    
27 
28 class Trace
29 {
30 public:
31     Trace(const char* s,Channel* c = TraceChannel::Instance())
32     {
33         if (trace_debug)
34         {
35             name = s;
36             cp = c;;
37             if (cp && cp->trace_file)
38             {
39                 *cp->trace_file << "Trace begin : " << name << endl;
40             }
41         }
42     }
43     ~Trace()
44     {
45         if (trace_debug)
46         {
47             if (cp && cp->trace_file)
48             {
49                 *cp->trace_file << "Trace end : " << name <<endl;
50             }
51         }
52     }
53 private:
54     Channel* cp;
55     const char* name;
56 };
57 
58 //传递类名给Obj_trace，可以作为待跟踪类的基类或成员变量存在
59 template<class T>
60 class Obj_trace
61 {
62 public:
63     Obj_trace(Channel* c = TraceChannel::Instance()) : ct(++count)
64     {
65         if (trace_debug)
66         {
67             cp = c;
68             if (cp && cp->trace_file)
69             {
70                 *cp->trace_file << "Trace obj begin : " << typeid(T).name() << " "<< ct << " constructed" << endl;
71             }
72         }
73     }
74     ~Obj_trace()
75     {
76         if (trace_debug)
77         {
78             if (cp && cp->trace_file)
79             {
80                 *cp->trace_file << "Trace obj end : " << typeid(T).name() << " "<< ct << " destoryed" << endl;
81             }
82         }
83     }
84 private:
85     Channel* cp;
86     const char* name;
87     static int count;
88     int ct;
89 };
90 
91 //每个不同的type类型都有唯一对应的count
92 template<class T>
93 int Obj_trace<T>::count = 0;