Ｃ++ 实现线程池的精典模型

        什么时候需要创建线程池呢？简单的说，如果一个应用需要频繁的创建和销毁线程，而任务执行的时间又非常短，这样线程创建和销毁的带来的开销就不容忽视，这时也是线程池该出场的机会了。如果线程创建和销毁时间相比任务执行时间可以忽略不计，则没有必要使用线程池了。

下面列出线程的一些重要的函数

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
				   void *(*start_routine) (void *), void *arg);
void pthread_exit(void *retval);

int pthread_mutex_destroy(pthread_mutex_t *mutex);
int pthread_mutex_init(pthread_mutex_t *restrict mutex,
					   const pthread_mutexattr_t *restrict attr);
int pthread_mutex_lock(pthread_mutex_t *mutex);
int pthread_mutex_trylock(pthread_mutex_t *mutex);
int pthread_mutex_unlock(pthread_mutex_t *mutex);

int pthread_cond_destroy(pthread_cond_t *cond);
int pthread_cond_init(pthread_cond_t *restrict cond,
					  const pthread_condattr_t *restrict attr);
int pthread_cond_destroy(pthread_cond_t *cond);
int pthread_cond_init(pthread_cond_t *restrict cond,
					  const pthread_condattr_t *restrict attr);
int pthread_cond_broadcast(pthread_cond_t *cond);
int pthread_cond_signal(pthread_cond_t *cond);

下面是用Ｃ++实现线程池源码：
在该源码中，有两个文件，一个头文件pmutil.h, 一个源文件pmulti.cpp文件
下面是　pmuti.h 文件

#include <pthread.h>
	  typedef struct  worker_node{ /*任务结点*/
		  void *(*process)(void *arg);
		  void *arg;
		  worker_node *next;
  }worker_node;
  typedef struct worker_queue{/*任务队列*/
  private:
	  worker_node * head ,*tail ;
	  int cur_size ;
	  pthread_cond_t ready ;/**保持同步*/
	  pthread_mutex_t mutex ; /**保持互斥信号*/
	  bool destroy ;
  public:
	  worker_queue(); 
	  ~worker_queue();
	  int clean();　　　/*清空队列*/
	  int in_queue(const worker_node *node); 　/*任务入队*/
	  worker_node * out_queue();　/*任务出队*/

  } worker_queue ;


  class pmulti{
  private:
	  pthread_t * threads ;
	  unsigned int thread_num;
	  mutable worker_queue * w_queue;
	  bool is_init;
	  bool is_destroy;
	  enum {QUEUE_MAX_SIZE=100};
  public:
	  pmulti();
	  ~pmulti();
	  int init(unsigned int num=10);
	  static void * thread_fun(void *arg);　/*线程执行主函数*/
	  int add_worker(const worker_node * node);　/*增加任务*/

	  int destroy();
  };

  pmulti.cpp文件

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include "multi.h"
worker_queue::worker_queue():head(NULL),tail(NULL),cur_size(0),destroy(false){
	pthread_mutex_init(&mutex,NULL);
	pthread_cond_init(&ready,NULL);
}
worker_queue::~worker_queue(){
	clean();
	destroy = true ;
	pthread_cond_broadcast(&ready);
	pthread_mutex_destroy(&mutex); 
	pthread_cond_destroy(&ready);
}   
int worker_queue::clean(){ 
	worker_node* temp;
	pthread_mutex_lock(&mutex);
	while(NULL!=head){
		temp = head ;
		head = head->next ; 
		delete temp ;
	}
	tail=head=NULL;
	cur_size = 0;
	pthread_mutex_unlock(&mutex);
	return 0;
}
int worker_queue::in_queue(const worker_node *node){
	worker_node *temp;
	temp = new worker_node ;
	if(NULL == temp) return -1 ; //new err ;
	*temp = *node ;
	pthread_mutex_lock(&mutex);

	if(NULL==head){
		head=tail=temp;
	}else{
		tail->next=temp ;
		tail = temp ;
		tail->next = NULL;
	}
	cur_size++;
	pthread_mutex_unlock(&mutex);
	pthread_cond_signal(&ready);
	return 0 ;
}
worker_node * worker_queue::out_queue(){ //out of the queue
	pthread_mutex_lock(&mutex);
	while((NULL==head) && (false == destroy))  { //queue empty
		pthread_cond_wait(&ready,&mutex);
	}
	//      assert(head!=NULL);
	//      assert(cur_size!=0);
	if(destroy){
		pthread_mutex_unlock(&mutex);
		return NULL;
	}
	worker_node *temp;
	temp = head ;
	head = head->next ;
	cur_size -- ;


	pthread_mutex_unlock(&mutex);
	return temp;
}
pmulti::pmulti():
is_init(false),thread_num(0),w_queue(NULL),threads(NULL),is_destroy(false){
}
pmulti::~pmulti(){
}
int pmulti::init(unsigned int thr_num){
	if(is_init)
		return -1;//alread init 
	int i;
	//pool = new thread_pool;
	//if(NULL == pool)      return -2;//new error
	//bzero(pool,sizeof(thread_pool));
	w_queue = new worker_queue ;
	if(NULL == w_queue)     return -2;//new error
	thread_num = thr_num;
	threads = new pthread_t[thr_num] ;
	for(i=0;i<thr_num;i++){
		if(0!=pthread_create((threads+i),NULL,thread_fun,(void*)this ))
			printf("pthread_create error\n");
	} 
	is_destroy = false ;
	is_init = true;
	return 0;
}
int pmulti::add_worker(const worker_node * node){
	return  w_queue->in_queue(node);
}
int pmulti::destroy(){
	int i=0;
	char* res;
	is_destroy = true ;
	if(NULL != w_queue)            
		delete w_queue;        
	for(i=0;i<thread_num;i++){               
		pthread_join(threads[i],(void**)&res);                
		printf("joined :%lld  end;\n",res);        
	}        
	if(thread_num > 0)  
		delete[] threads;        
	return 0;
}
void* pmulti::thread_fun(void*arg){        
	printf("thread num:%lld\n",pthread_self());        
	pmulti *pm =(pmulti*)arg;        
	worker_node * node ;        
	while(1){               
		if(pm->is_destroy)                        
			pthread_exit(NULL);                
		node = pm->w_queue->out_queue();                
		if((NULL == node)|| (pm->is_destroy))                        
			pthread_exit(NULL);                
		node->process(node->arg);                
		printf("thread_fun:%lld run\n",pthread_self());        
	}        
	return (void*)pthread_self();
}

void * test(void* i){        
	printf("test:%d\n",( int)i);        
	sleep(1);        
	return NULL;
}
int main(int argc,char ** args){        
	printf("this is main!\n");        
	class pmulti pm;        
	pm.init(15);        
	worker_node no ;        
	for(int i=0;i<5;i++){                
		no.process = &test ;                
		no.arg = (void*)(i*2);                
		pm.add_worker(&no);        
	}        
	sleep(5);        
	pm.destroy();     　 
	return 0;
}

运行结果：
g++ multi.cpp multi.h -lpthread -o multi
[test@localhost multi_thread]$ ./multi 
this is main!
thread num:24531909488
test:0
thread num:3046583152
test:2
thread num:3036093296
test:4
thread num:3025603440
test:6
thread num:3015113584
test:8
thread num:3004623728
thread num:3067562864
thread num:2994133872
thread num:2983644016
thread num:2973154160
thread num:2962664304
thread num:2952174448
thread num:2941684592
thread num:2931194736
thread num:3078052720
thread_fun:24531909488 run
thread_fun:3046583152 run
thread_fun:3036093296 run
thread_fun:3025603440 run
thread_fun:3015113584 run
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;
joined :0  end;