分类： C/C++
2013-01-31 09:49:36
C++程序的设计机制3 RAII机制(3)
为了管理内存等资源，C++程序员通常采用RAII机制（资源获取即初始化），在使用资源的类的构造函数中申请资源，然后使用，最后在析构函数中释放资源。今天本文为你介绍RAII机制，一起来看。
AD：
3）锁操作
1. /*
2. * =====================================================================================
3. *
4. * Filename: threadlock.cpp
5. *
6. * Description: Lock for RAII
7. *
8. * Version: 1.0
9. * Created: 05/09/2011 10:16:13 PM
10.* Revision: none
11.* Compiler: g++
12.*
13.* Author: gnuhpc (http://blog.csdn.net/gnuhpc), warmbupt@gmail.com
14.*
15.* =====================================================================================
16.*/
17.#include
18.#include
19.#include
20.int counter = 0;
21.void* routine(void *ptr);
22.pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
23.class NonCopyable
24.{
25.public:
26.NonCopyable(){};
27.private:
28.NonCopyable (NonCopyable const &); // private copy constructor
29.NonCopyable & operator = (NonCopyable const &); // private assignment operator
30.};
31.class ScopeMutex:NonCopyable
32.{
33.public:
34.ScopeMutex(pthread_mutex_t* mutex):mutex_(mutex){
35.pthread_mutex_lock( mutex_ );
36.}
37.~ScopeMutex(){
38.pthread_mutex_unlock( mutex_ );
39.}
40.private:
41.pthread_mutex_t *mutex_;
42.};
43.int main(int argc, char *argv[])
44.{
45.int rc1, rc2;
46.pthread_t thread1, thread2;
47.if( (rc1=pthread_create( &thread1, NULL, routine, NULL)) )
48.{
49.printf("Thread creation failed: %d\n", rc1);
50.}
51.if( (rc2=pthread_create( &thread2, NULL, routine, NULL)) )
52.{
53.printf("Thread creation failed: %d\n", rc1);
54.}
55.pthread_join( thread1, NULL);
56.pthread_join( thread2, NULL);
57.}
58.void* routine(void *ptr)
59.{
60.ScopeMutex scopeMutex(&mutex);
61.counter++;
62.printf("%d\n",counter);
63.}
2.总结
RAII机制保证了异常安全，并且也为程序员在编写动态分配内存的程序时提供了安全保证。缺点是有些操作可能会抛出异常，如果放在析构函数中进行则不能将错误传递出去，那么此时析构函数就必须自己处理异常。这在某些时候是很繁琐的。参考资料
