在上一篇中介紹了創(chuàng)建Thread的兩種方法：從Thread類繼承或者實現(xiàn)Runnable接口。有時候這并不是特別方便，我們需要的是更靈活的方法，比如像boost庫中的Thread一樣可以用普通函數(shù)和函數(shù)對象
(
functor?and
function object)作為構(gòu)造函數(shù)參數(shù)。如果你熟悉STL，你應(yīng)該熟悉bind1st和bind2nd這兩個函數(shù)配接器(
function adapter)，bind1st和bind2nd可以將一個二元函數(shù)(
binary function)轉(zhuǎn)換成一元函數(shù)(
unary function)。為了使Thread類能夠用普通函數(shù)和函數(shù)對象作為參數(shù)，我們需要一個bind將一元函數(shù)轉(zhuǎn)換成無參函數(shù)：
bind.h
?1?#ifndef?BIND_H
?2?#define?BIND_H
?3?
?4?template?<class?_Result>
?5?struct?trivial_function?{
?6?????typedef?_Result?result_type;
?7?};
?8?
?9?template?<class?_Operation>
10?class?binder?:?public?trivial_function<typename?_Operation::result_type>?{
11?public:
12?????binder(const?_Operation& x,?const?typename?_Operation::argument_type& y)
13?????????:op(x),?value(y)?{}
14?????typename?_Operation::result_type?operator()()?const?{
15?????????return?op(value);
16?????}
17?protected:
18?????_Operation?op;
19?????typename?_Operation::argument_type?value;
20?};
21?
22?template?<class?_Operation,?class?_Tp>
23?inline?binder<_Operation>?
24?bind(const?_Operation&?__fn,?const?_Tp&?__x)?
25?{
26?????typedef?typename?_Operation::argument_type?_Arg_type;
27?????return?binder<_Operation>(__fn,?_Arg_type(__x));
28?}
29?
30?#endif/*BIND_H*/
有了bind我們還需要修改Thread類的構(gòu)造函數(shù)，顯然我們必須將構(gòu)造函數(shù)聲明為成員模板(還有一種方法也可以達到同樣的目的，就是把Thread類聲明為模板，但是這樣的設(shè)計好像不太好)，這樣才能夠讓Thread類的構(gòu)造函數(shù)可以接受各種類型的參數(shù)，修改后的構(gòu)造函數(shù)應(yīng)該能夠使用如下三種類型的參數(shù)：
1.Runnable *
2.no argument function
3.no argument functor
下面是修改后的頭文件：
runnable.h
?1?#ifndef?RUNNABLE_H
?2?#define?RUNNABLE_H
?3?
?4?struct?Runnable?{
?5?????virtual?void?run()?=?0;
?6?????virtual?~Runnable()?{}
?7?};
?8?
?9?template?<class?T>
10?class?RunnableFunctor?:?public?Runnable?{
11?public:
12?????RunnableFunctor(const?T& f)?:_func(f)?{}
13?????virtual?void?run()?{?_func();?}
14?private:
15?????T?_func;
16?};
17?
18?//base?template?for?no?argument?functor
19?template?<class?T>
20?struct?FuncImpl?{
21?????static?Runnable*?transfer(const?T& t)?{
22?????????return?new?RunnableFunctor<T>(t);
23?????}
24?};
25?
26?//partial?specialization?for?T*
27?template?<class?T>
28?struct?FuncImpl<T*>?{
29?????static?Runnable*?transfer(T* t)?{
30?????????return?t;
31?????}
32?};
33?
34?//partial?specialization?for?no?argument?function
35?template?<class?T>
36?struct?FuncImpl<T?(*)()>?{
37?????static?Runnable*?transfer(T?(*t)())?{
38?????????return?new?RunnableFunctor<T?(*)()>(t);
39?????}
40?};
41?
42?template?<class?T>
43?inline?Runnable*?transfer(const?T& t)?{
44?????return?FuncImpl<T>::transfer(t);
45?}
46?
47?#endif/*RUNNABLE_H*/
thread.h
?1?#ifndef?THREAD_H
?2?#define?THREAD_H
?3?
?4?#include?<windows.h>
?5?#include?"bind.h"
?6?#include?"runnable.h"
?7?
?8?#define?CLASS_UNCOPYABLE(classname)?\
?9?????private:?\
10?????classname(const?classname&);?\
11?????classname&?operator=(const?classname&);
12?
13?class?Thread?:?public?Runnable?{
14?????CLASS_UNCOPYABLE(Thread)
15?public:
16?????Thread()
17?????????:_target(0)
18?????????,_handle(0)?{
19?
20?????}
21?????template?<class?T>
22?????explicit?Thread(const?T& op)
23?????????:_target(transfer(op))
24?????????,_handle(0)?{
25?
26?????}
27?????virtual?~Thread();
28?????virtual?void?run()?{}
29?????void?start();
30?????void?join();
31?private:
32?????static?unsigned?__stdcall?threadProc(void* param);
33?private:
34?????Runnable* _target;
35?????HANDLE?_handle;
36?};
37?
38?#endif/*THREAD_H*/
thread.cpp和前一篇的幾乎一樣，唯一的不同是去掉了構(gòu)造函數(shù)Thread(Runnable *)，因為現(xiàn)在的構(gòu)造函數(shù)改成了成員模板，實現(xiàn)也放在thread.h中了。現(xiàn)在的構(gòu)造函數(shù)能夠接受各種類型的參數(shù)，主要歸功于模板函數(shù)transfer，實現(xiàn)代碼在runnable.h中，主要技巧是用類的偏特化模擬函數(shù)模板的偏特化，不明白的請看
為什么不要特化函數(shù)模版。
下面是測試代碼：
test.cpp
?1?#include?"thread.h"
?2?#include?<iostream>
?3?#include?<functional>
?4?
?5?using?namespace?std;
?6?
?7?//no?argument?function
?8?void?print()?{
?9?????cout?<<?"print"?<<?endl;
10?}
11?
12?//unary?function
13?void?print1(int?n)?{
14?????cout?<<?"print1"?<<?endl;
15?}
16?
17?//binary?function
18?void?print2(int?m,?int?n)?{
19?????cout?<<?"print2"?<<?endl;
20?}
21?
22?
23?//no?argument?functor
24?struct?PrintFunctor?{
25?????void?operator()()?const?{
26?????????cout?<<?"PrintFunctor"?<<?endl;
27?????}
28?};
29?
30?//unary?functor
31?struct?PrintFunctor1?:?public?unary_function<int,?void>?{
32?????void?operator()(int?n)?const?{
33?????????cout?<<?"PrintFunctor1"?<<?endl;
34?????}
35?};
36?
37?//binary?functor
38?struct?PrintFunctor2?:?public?binary_function<int,?int,?void>?{
39?????void?operator()(int?m,?int?n)?const?{
40?????????cout?<<?"PrintFunctor2"?<<?endl;
41?????}
42?};
43?
44?int?main()?{
45?
46?????//construct?Thread?with?no?argument?function
47?????Thread?thread1(&print);
48?????thread1.start();
49?
50?????//construct?Thread?with?unary?function
51?????Thread?thread2(bind(ptr_fun(print1),?5));
52?????thread2.start();
53?
54?????//construct?Thread?with?binary?function
55?????Thread?thread3(bind(bind1st(ptr_fun(print2),?1),?2));
56?????thread3.start();
57?
58?
59?????//construct?Thread?with?no?argument?functor
60?????Thread?thread4((PrintFunctor()));
61?????thread4.start();
62?
63?????//construct?Thread?with?unary?functor
64?????Thread?thread5(bind(PrintFunctor1(),?5));
65?????thread5.start();
66?
67?????//construct?Thread?with?binary?functor
68?????Thread?thread6(bind(bind1st(PrintFunctor2(),?1),?2));
69?????thread6.start();
70?
71?????thread1.join();
72?????thread2.join();
73?????thread3.join();
74?????thread4.join();
75?????thread5.join();
76?????thread6.join();
77?
78?????return?0;
79?}
當(dāng)然了，上面的并不是全部，修改后的Thread類不僅能夠使用原先的從Thread類繼承或者實現(xiàn)Runnable接口的方法，還可以使用任何無參函數(shù)或無參函數(shù)對象。除了test.cpp里示范的，你甚至可以用bind,bind1st,bind2st,mem_fun,mem_fun_ref的組合來用某個類的成員函數(shù)作為參數(shù)，具有超強的靈活性。
目前實現(xiàn)的這些都是Thread類最基本的功能，其他功能如設(shè)置線程優(yōu)先級，掛起或恢復(fù)線程，異常處理等具體實現(xiàn)都比較簡單，這這里就不一一實現(xiàn)了。
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