Ｃ++ 實現線程池的精典模型

        什麼時候需要建立線程池呢？簡單的說，如果一個應用需要頻繁的建立和銷毀線程，而任務執行的時間又非常短，這樣線程建立和銷毀的帶來的開銷就不容忽視，這時也是線程池該出場的機會了。如果線程建立和銷毀時間相比任務執行時間可以忽略不計，則沒有必要使用線程池了。

下面列出線程的一些重要的函數

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++實現線程池源碼：
在該源碼中，有兩個檔案，一個標頭檔pmutil.h, 一個源檔案pmulti.cpp檔案
下面是　pmuti.h 檔案

#include <pthread.h>  typedef struct  worker_node{ /*任務結點*/  void *(*process)(void *arg);  void *arg;  worker_node *next;  }worker_node;  typedef struct worker_queue{/*任務隊列*/  private:  worker_node * head ,*tail ;  int cur_size ;  pthread_cond_t ready ;/**保持同步*/  pthread_mutex_t mutex ; /**保持互斥訊號*/  bool destroy ;  public:  worker_queue();   ~worker_queue();  int clean();　　　/*清空隊列*/  int in_queue(const worker_node *node); 　/*任務入隊*/  worker_node * out_queue();　/*任務出隊*/  } 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);　/*線程執行主函數*/  int add_worker(const worker_node * node);　/*增加任務*/  int destroy();  };

  pmulti.cpp檔案

#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 queuepthread_mutex_lock(&mutex);while((NULL==head) && (false == destroy))  { //queue emptypthread_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 errorthread_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;}

運行結果：
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;