linux高并发web服务器开发(web服务器)19_strftime，libevent实现httpserver，线程池原理，结构体，使用，干活的线程的回调函数，管理者线程回调函数

01 strftime

strftime 函数
头文件: time.h
函数功能: 将时间格式化，或者说格式化一个时间字符串。
函数原型:

size_t strftime(
char *strDest,
size_t maxsize,
const char *format,
const struct tm *timeptr
);

format
○ %a 星期几的简写
○ %A 星期几的全称
○ %b 月份的简写
○ %B 月份的全称
○ %c 标准的日期的时间串
○ %C 年份的前两位数字
○ %d 十进制表示的每月的第几天
○ %D 月/天/年
○ %e 在两字符域中，十进制表示的每月的第几天
○ %F 年-月-日
○ %g 年份的后两位数字，使用基于周的年
○ %G 年份，使用基于周的年
○ %h 简写的月份名
○ %H 24小时制的小时
○ %I 12小时制的小时
○ %j 十进制表示的每年的第几天
○ %m 十进制表示的月份
○ %M 十时制表示的分钟数
○ %p 本地的AM或PM的等价显示
○ %r 12小时的时间
○ %R 显示小时和分钟：hh:mm
○ %S 十进制的秒数
○ %t 水平制表符
○ %T 显示时分秒：hh:mm:ss
○ %u 每周的第几天，星期一为第一天 （值从1到7，星期一为1）
○ %U 第年的第几周，把星期日作为第一天（值从0到53）
○ %V 每年的第几周，使用基于周的年
○ %w 十进制表示的星期几（值从0到6，星期天为0）
○ %W 每年的第几周，把星期一做为第一天（值从0到53）
○ %x 标准的日期串
○ %X 标准的时间串
○ %y 不带世纪的十进制年份（值从0到99）
○ %Y 带世纪部分的十制年份
○ %z，%Z 时区名称，如果不能得到时区名称则返回空字符。

02 libevent实现httpserver

libevent_http.h:

#ifndef _LIBEVENT_HTTP_H
#define _LIBEVENT_HTTP_H

#include 

void conn_eventcb(struct bufferevent *bev, short events, void *user_data);

void conn_readcb(struct bufferevent *bev, void *user_data);

const char *get_file_type(char *name);

int hexit(char c);

void listener_cb(struct evconnlistener *listener, evutil_socket_t fd,
                 struct sockaddr *sa, int socklen, void *user_data);

int response_http(struct bufferevent *bev, const char *method, char *path);

int send_dir(struct bufferevent *bev,const char *dirname);

int send_error(struct bufferevent *bev);

int send_file_to_http(const char *filename, struct bufferevent *bev);

int send_header(struct bufferevent *bev, int no, const char* desp, const char *type, long len);

void signal_cb(evutil_socket_t sig, short events, void *user_data);

void strdecode(char *to, char *from);

void strencode(char* to, size_t tosize, const char* from);

#endif

libevent_http.c:

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "libevent_http.h"

#define _HTTP_CLOSE_ "Connection: close\r\n"

int response_http(struct bufferevent *bev, const char *method, char *path)
{
    if(strcasecmp("GET", method) == 0){
        //get method ...
        strdecode(path, path);
        char *pf = &path[1];

        if(strcmp(path, "/") == 0 || strcmp(path, "/.") == 0)
        {
            pf="./";
        }

        printf("***** http Request Resource Path =  %s, pf = %s\n", path, pf);

        struct stat sb;
        if(stat(pf,&sb) < 0)
        {
            perror("open file err:");
            send_error(bev);
            return -1;
        }

        if(S_ISDIR(sb.st_mode))//处理目录
        {
            //应该显示目录列表
            send_header(bev, 200, "OK", get_file_type(".html"), -1);
            send_dir(bev, pf);
        }
        else //处理文件
        {
            send_header(bev, 200, "OK", get_file_type(pf), sb.st_size);
            send_file_to_http(pf, bev);
        }
    }

    return 0;
}

/*
     *charset=iso-8859-1	西欧的编码，说明网站采用的编码是英文；
     *charset=gb2312		说明网站采用的编码是简体中文；
     *charset=utf-8			代表世界通用的语言编码；
     *						可以用到中文、韩文、日文等世界上所有语言编码上
     *charset=euc-kr		说明网站采用的编码是韩文；
     *charset=big5			说明网站采用的编码是繁体中文；
     *
     *以下是依据传递进来的文件名，使用后缀判断是何种文件类型
     *将对应的文件类型按照http定义的关键字发送回去
*/
const char *get_file_type(char *name)
{
    char* dot;

    dot = strrchr(name, '.');	//自右向左查找‘.’字符;如不存在返回NULL

    if (dot == (char*)0)
        return "text/plain; charset=utf-8";
    if (strcmp(dot, ".html") == 0 || strcmp(dot, ".htm") == 0)
        return "text/html; charset=utf-8";
    if (strcmp(dot, ".jpg") == 0 || strcmp(dot, ".jpeg") == 0)
        return "image/jpeg";
    if (strcmp(dot, ".gif") == 0)
        return "image/gif";
    if (strcmp(dot, ".png") == 0)
        return "image/png";
    if (strcmp(dot, ".css") == 0)
        return "text/css";
    if (strcmp(dot, ".au") == 0)
        return "audio/basic";
    if (strcmp( dot, ".wav") == 0)
        return "audio/wav";
    if (strcmp(dot, ".avi") == 0)
        return "video/x-msvideo";
    if (strcmp(dot, ".mov") == 0 || strcmp(dot, ".qt") == 0)
        return "video/quicktime";
    if (strcmp(dot, ".mpeg") == 0 || strcmp(dot, ".mpe") == 0)
        return "video/mpeg";
    if (strcmp(dot, ".vrml") == 0 || strcmp(dot, ".wrl") == 0)
        return "model/vrml";
    if (strcmp(dot, ".midi") == 0 || strcmp(dot, ".mid") == 0)
        return "audio/midi";
    if (strcmp(dot, ".mp3") == 0)
        return "audio/mpeg";
    if (strcmp(dot, ".ogg") == 0)
        return "application/ogg";
    if (strcmp(dot, ".pac") == 0)
        return "application/x-ns-proxy-autoconfig";

    return "text/plain; charset=utf-8";
}

int send_file_to_http(const char *filename, struct bufferevent *bev)
{
    int fd = open(filename, O_RDONLY);
    int ret = 0;
    char buf[4096] = {0};

    while(  (ret = read(fd, buf, sizeof(buf)) ) )
    {
        bufferevent_write(bev, buf, ret);
        memset(buf, 0, ret);
    }
    close(fd);
    return 0;
}

int send_header(struct bufferevent *bev, int no, const char* desp, const char *type, long len)
{
    char buf[256]={0};

    sprintf(buf, "HTTP/1.1 %d %s\r\n", no, desp);
    //HTTP/1.1 200 OK\r\n
    bufferevent_write(bev, buf, strlen(buf));
    // 文件类型
    sprintf(buf, "Content-Type:%s\r\n", type);
    bufferevent_write(bev, buf, strlen(buf));
    // 文件大小
    sprintf(buf, "Content-Length:%ld\r\n", len);
    bufferevent_write(bev, buf, strlen(buf));
    // Connection: close
    bufferevent_write(bev, _HTTP_CLOSE_, strlen(_HTTP_CLOSE_));
    //send \r\n
    bufferevent_write(bev, "\r\n", 2);

    return 0;
}

int send_error(struct bufferevent *bev)
{
    send_header(bev,404, "File Not Found", "text/html", -1);
    send_file_to_http("404.html", bev);
    return 0;
}

int send_dir(struct bufferevent *bev,const char *dirname)
{
    char encoded_name[1024];
    char path[1024];
    char timestr[64];
    struct stat sb;
    struct dirent **dirinfo;

    char buf[4096] = {0};
    sprintf(buf, "", dirname);
    sprintf(buf+strlen(buf), "
当前目录：%s
", dirname);
    //添加目录内容
    int num = scandir(dirname, &dirinfo, NULL, alphasort);
    for(int i=0; id_name);

        sprintf(path, "%s%s", dirname, dirinfo[i]->d_name);
        printf("############# path = %s\n", path);
        if (lstat(path, &sb) < 0)
        {
            sprintf(buf+strlen(buf), 
                    "\n", 
                    encoded_name, dirinfo[i]->d_name);
        }
        else
        {
            strftime(timestr, sizeof(timestr), 
                     "  %d  %b   %Y  %H:%M", localtime(&sb.st_mtime));
            if(S_ISDIR(sb.st_mode))
            {
                sprintf(buf+strlen(buf), 
                        "\n",
                        encoded_name, dirinfo[i]->d_name, timestr, sb.st_size);
            }
            else
            {
                sprintf(buf+strlen(buf), 
                        "\n", 
                        encoded_name, dirinfo[i]->d_name, timestr, sb.st_size);
            }
        }
        bufferevent_write(bev, buf, strlen(buf));
        memset(buf, 0, sizeof(buf));
    }
    sprintf(buf+strlen(buf), "
%s
%s/
%s
%ld
%s
%s
%ld
");
    bufferevent_write(bev, buf, strlen(buf));
    printf("################# Dir Read OK !!!!!!!!!!!!!!\n");

    return 0;
}

void conn_readcb(struct bufferevent *bev, void *user_data)
{
    printf("******************** begin call %s.........\n",__FUNCTION__);
    char buf[4096]={0};
    char method[50], path[4096], protocol[32];
    bufferevent_read(bev, buf, sizeof(buf));
    printf("buf[%s]\n", buf);
    sscanf(buf, "%[^ ] %[^ ] %[^ \r\n]", method, path, protocol);
    printf("method[%s], path[%s], protocol[%s]\n", method, path, protocol);
    if(strcasecmp(method, "GET") == 0)
    {
        response_http(bev, method, path);
    }
    printf("******************** end call %s.........\n", __FUNCTION__);
}

void conn_eventcb(struct bufferevent *bev, short events, void *user_data)
{
    printf("******************** begin call %s.........\n", __FUNCTION__);
    if (events & BEV_EVENT_EOF)
    {
        printf("Connection closed.\n");
    }
    else if (events & BEV_EVENT_ERROR)
    {
        printf("Got an error on the connection: %s\n",
               strerror(errno));
    }

    bufferevent_free(bev);
    printf("******************** end call %s.........\n", __FUNCTION__);
}

void signal_cb(evutil_socket_t sig, short events, void *user_data)
{
    struct event_base *base = user_data;
    struct timeval delay = { 1, 0 };

    printf("Caught an interrupt signal; exiting cleanly in one seconds.\n");
    event_base_loopexit(base, &delay);
}

void listener_cb(struct evconnlistener *listener, 
                 evutil_socket_t fd,struct sockaddr *sa, int socklen, void *user_data)
{
    printf("******************** begin call-------%s\n",__FUNCTION__);
    struct event_base *base = user_data;
    struct bufferevent *bev;
    printf("fd is %d\n",fd);
    bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
    if (!bev)
    {
        fprintf(stderr, "Error constructing bufferevent!");
        event_base_loopbreak(base);
        return;
    }
    bufferevent_flush(bev, EV_READ | EV_WRITE, BEV_NORMAL);
    bufferevent_setcb(bev, conn_readcb, NULL, conn_eventcb, NULL);
    bufferevent_enable(bev, EV_READ | EV_WRITE);

    printf("******************** end call-------%s\n",__FUNCTION__);
}

/*
 * 这里的内容是处理%20之类的东西！是"解码"过程。
 * %20 URL编码中的‘ ’(space)
 * %21 '!' %22 '"' %23 '#' %24 '$'
 * %25 '%' %26 '&' %27 ''' %28 '('......
 * 相关知识html中的‘ ’(space)是 
 */
void strdecode(char *to, char *from)
{
    for ( ; *from != '\0'; ++to, ++from)
    {
        if (from[0] == '%' && isxdigit(from[1]) && isxdigit(from[2]))
        {
            // 依次判断from中 %20 三个字符
            *to = hexit(from[1])*16 + hexit(from[2]);
            // 移过已经处理的两个字符(%21指针指向1),表达式3的++from还会再向后移一个字符
            from += 2;
        }
        else
        {
            *to = *from;
        }
    }
    *to = '\0';
}

//16进制数转化为10进制, return 0不会出现
int hexit(char c)
{
    if (c >= '0' && c <= '9')
        return c - '0';
    if (c >= 'a' && c <= 'f')
        return c - 'a' + 10;
    if (c >= 'A' && c <= 'F')
        return c - 'A' + 10;

    return 0;
}

// "编码"，用作回写浏览器的时候，将除字母数字及/_.-~以外的字符转义后回写。
// strencode(encoded_name, sizeof(encoded_name), name);
void strencode(char* to, size_t tosize, const char* from)
{
    int tolen;

    for (tolen = 0; *from != '\0' && tolen + 4 < tosize; ++from)
    {
        if (isalnum(*from) || strchr("/_.-~", *from) != (char*)0)
        {
            *to = *from;
            ++to;
            ++tolen;
        }
        else
        {
            sprintf(to, "%%%02x", (int) *from & 0xff);
            to += 3;
            tolen += 3;
        }
    }
    *to = '\0';
}

main.c:

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "libevent_http.h"

int main(int argc, char **argv)
{
    if(argc < 3)
    {
        printf("./event_http port path\n");
        return -1;
    }
    if(chdir(argv[2]) < 0) {
        printf("dir is not exists: %s\n", argv[2]);
        perror("chdir err:");
        return -1;
    }

    struct event_base *base;
    struct evconnlistener *listener;
    struct event *signal_event;

    struct sockaddr_in sin;
    base = event_base_new();
    if (!base)
    {
        fprintf(stderr, "Could not initialize libevent!\n");
        return 1;
    }

    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_port = htons(atoi(argv[1]));

    // 创建监听的套接字，绑定，监听，接受连接请求
    listener = evconnlistener_new_bind(base, listener_cb, (void *)base,
                    LEV_OPT_REUSEABLE | LEV_OPT_CLOSE_ON_FREE, -1,
                    (struct sockaddr*)&sin, sizeof(sin));
    if (!listener)
    {
        fprintf(stderr, "Could not create a listener!\n");
        return 1;
    }

    // 创建信号事件, 捕捉并处理
    signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);
    if (!signal_event || event_add(signal_event, NULL)<0) 
    {
        fprintf(stderr, "Could not create/add a signal event!\n");
        return 1;
    }

    // 事件循环
    event_base_dispatch(base);

    evconnlistener_free(listener);
    event_free(signal_event);
    event_base_free(base);

    printf("done\n");

    return 0;
}

makefile

#makefile 

target = http_server
$(target):libevent_http.c main.c
	gcc -o $@ $^ -g -levent

.PHONY:clean
clean:
	-rm -f $(target)

03 线程池原理

1.初始化一些线程
○ 管理者线程——不处理任务
○ 工作的线程——只负责处理任务(去任务队列中领任务并处理)
○ 初始化的给定一最小线程数

2.需要有一个管理者线程
○ 每隔一段时间去判断一次
○ 什么时候需要创建
 指定一个峰值
工作的线程超过85%
工作/存活>0.85
 超过峰值
创建新的线程(每次创建10个)
○什么时候销毁
 工作的线程/存活的线程<20%
 按照一定的比例去杀死不干活的线程

3.线程工作的时候:
a. 处理数据的时候:
i. 互斥锁
ii. 条件变量

04 线程池结构体

/* 描述线程池相关信息 */
struct threadpool_t {
    pthread_mutex_t lock;               /* 用于锁住本结构体 */    
    pthread_mutex_t thread_counter;     /* 记录忙状态线程个数de琐 -- busy_thr_num */
    pthread_cond_t queue_not_full;      /* 当任务队列满时，添加任务的线程阻塞，等待此条件变量 */
    pthread_cond_t queue_not_empty;     /* 任务队列里不为空时，通知等待任务的线程 */

    pthread_t *threads;                 /* 存放线程池中每个线程的tid。数组 */
    pthread_t adjust_tid;               /* 存管理线程tid */
    threadpool_task_t *task_queue;      /* 任务队列 */

    int min_thr_num;                    /* 线程池最小线程数 */
    int max_thr_num;                    /* 线程池最大线程数 */
    int live_thr_num;                   /* 当前存活线程个数 */
    int busy_thr_num;                   /* 忙状态线程个数 */
    int wait_exit_thr_num;              /* 要销毁的线程个数 */

    int queue_front;                    /* task_queue队头下标 */
    int queue_rear;                     /* task_queue队尾下标 */
    int queue_size;                     /* task_queue队中实际任务数 */
    int queue_max_size;                 /* task_queue队列可容纳任务数上限 */

    int shutdown;                       /* 标志位，线程池使用状态，true或false */
};

05 如何使用线程池api

int main(void)
{
    /*threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);*/

    threadpool_t *thp = threadpool_create(3,100,100);/*创建线程池，池里最小3个线程，最大100，队列最大100*/
    printf("pool inited");

    //int *num = (int *)malloc(sizeof(int)*20);
    int num[20], i;
    for (i = 0; i < 20; i++) {
        num[i]=i;
        printf("add task %d\n",i);
        threadpool_add(thp, process, (void*)&num[i]);     /* 向线程池中添加任务 */
    }
    sleep(10);                                          /* 等子线程完成任务 */
    threadpool_destroy(thp);

    return 0;
}

06 初始化线程池的函数

threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size)
{
    int i;
    threadpool_t *pool = NULL;
    do {
        if((pool = (threadpool_t *)malloc(sizeof(threadpool_t))) == NULL) {  
            printf("malloc threadpool fail");
            break;/*跳出do while*/
        }

        pool->min_thr_num = min_thr_num;
        pool->max_thr_num = max_thr_num;
        pool->busy_thr_num = 0;
        pool->live_thr_num = min_thr_num;               /* 活着的线程数 初值=最小线程数 */
        pool->queue_size = 0;                           /* 有0个产品 */
        pool->queue_max_size = queue_max_size;
        pool->queue_front = 0;
        pool->queue_rear = 0;
        pool->shutdown = false;                         /* 不关闭线程池 */

        /* 根据最大线程上限数， 给工作线程数组开辟空间, 并清零 */
        pool->threads = (pthread_t *)malloc(sizeof(pthread_t)*max_thr_num); 
        if (pool->threads == NULL) {
            printf("malloc threads fail");
            break;
        }
        memset(pool->threads, 0, sizeof(pthread_t)*max_thr_num);

        /* 队列开辟空间 */
        pool->task_queue = (threadpool_task_t *)malloc(sizeof(threadpool_task_t)*queue_max_size);
        if (pool->task_queue == NULL) {
            printf("malloc task_queue fail");
            break;
        }

        /* 初始化互斥琐、条件变量 */
        if (pthread_mutex_init(&(pool->lock), NULL) != 0
                || pthread_mutex_init(&(pool->thread_counter), NULL) != 0
                || pthread_cond_init(&(pool->queue_not_empty), NULL) != 0
                || pthread_cond_init(&(pool->queue_not_full), NULL) != 0)
        {
            printf("init the lock or cond fail");
            break;
        }

        /* 启动 min_thr_num 个 work thread */
        for (i = 0; i < min_thr_num; i++) {
            pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);/*pool指向当前线程池*/
            printf("start thread 0x%x...\n", (unsigned int)pool->threads[i]);
        }
        pthread_create(&(pool->adjust_tid), NULL, adjust_thread, (void *)pool);/* 启动管理者线程 */

        return pool;

    } while (0);

    threadpool_free(pool);      /* 前面代码调用失败时，释放poll存储空间 */

    return NULL;
}

07 干活的线程的回调函数

线程阻塞条件:
任务对列如果为空 cond_empty
pthread_cond_wait(&cond_empty, &mutex);

任务队列中有数据:
激活阻塞在条件变量上的线程:
pthread_cond_signal(&cond_empty);
pthead_cond_broadcast(&cond_empty);

/* 线程池中各个工作线程 */
void *threadpool_thread(void *threadpool)
{
    threadpool_t *pool = (threadpool_t *)threadpool;
    threadpool_task_t task;

    while (true) {
        /* Lock must be taken to wait on conditional variable */
        /*刚创建出线程，等待任务队列里有任务，否则阻塞等待任务队列里有任务后再唤醒接收任务*/
        pthread_mutex_lock(&(pool->lock));

        /*queue_size == 0 说明没有任务，调 wait 阻塞在条件变量上, 若有任务，跳过该while*/
        while ((pool->queue_size == 0) && (!pool->shutdown)) {  
            printf("thread 0x%x is waiting\n", (unsigned int)pthread_self());
            pthread_cond_wait(&(pool->queue_not_empty), &(pool->lock));

            /*清除指定数目的空闲线程，如果要结束的线程个数大于0，结束线程*/
            if (pool->wait_exit_thr_num > 0) {
                pool->wait_exit_thr_num--;

                /*如果线程池里线程个数大于最小值时可以结束当前线程*/
                if (pool->live_thr_num > pool->min_thr_num) {
                    printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());
                    pool->live_thr_num--;
                    pthread_mutex_unlock(&(pool->lock));
                    pthread_exit(NULL);
                }
            }
        }

        /*如果指定了true，要关闭线程池里的每个线程，自行退出处理*/
        if (pool->shutdown) {
            pthread_mutex_unlock(&(pool->lock));
            printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());
            pthread_exit(NULL);     /* 线程自行结束 */
        }

        /*从任务队列里获取任务, 是一个出队操作*/
        task.function = pool->task_queue[pool->queue_front].function;
        task.arg = pool->task_queue[pool->queue_front].arg;

        pool->queue_front = (pool->queue_front + 1) % pool->queue_max_size;       /* 出队，模拟环形队列 */
        pool->queue_size--;

        /*通知可以有新的任务添加进来*/
        pthread_cond_broadcast(&(pool->queue_not_full));

        /*任务取出后，立即将 线程池琐 释放*/
        pthread_mutex_unlock(&(pool->lock));

        /*执行任务*/ 
        printf("thread 0x%x start working\n", (unsigned int)pthread_self());
        pthread_mutex_lock(&(pool->thread_counter));                            /*忙状态线程数变量琐*/
        pool->busy_thr_num++;                                                   /*忙状态线程数+1*/
        pthread_mutex_unlock(&(pool->thread_counter));
        (*(task.function))(task.arg);                                           /*执行回调函数任务*/
        //task.function(task.arg);                                              /*执行回调函数任务*/

        /*任务结束处理*/ 
        printf("thread 0x%x end working\n", (unsigned int)pthread_self());
        pthread_mutex_lock(&(pool->thread_counter));
        pool->busy_thr_num--;                                       /*处理掉一个任务，忙状态数线程数-1*/
        pthread_mutex_unlock(&(pool->thread_counter));
    }

    pthread_exit(NULL);
}

08 管理者线程回调函数

/* 管理线程 */
void *adjust_thread(void *threadpool)
{
    int i;
    threadpool_t *pool = (threadpool_t *)threadpool;
    while (!pool->shutdown) {

        sleep(DEFAULT_TIME);                                    /*定时 对线程池管理*/

        pthread_mutex_lock(&(pool->lock));
        int queue_size = pool->queue_size;                      /* 关注 任务数 */
        int live_thr_num = pool->live_thr_num;                  /* 存活 线程数 */
        pthread_mutex_unlock(&(pool->lock));

        pthread_mutex_lock(&(pool->thread_counter));
        int busy_thr_num = pool->busy_thr_num;                  /* 忙着的线程数 */
        pthread_mutex_unlock(&(pool->thread_counter));

        /* 创建新线程 算法： 任务数大于最小线程池个数, 且存活的线程数少于最大线程个数时 如：30>=10 && 40<100*/
        if (queue_size >= MIN_WAIT_TASK_NUM && live_thr_num < pool->max_thr_num) {
            pthread_mutex_lock(&(pool->lock));  
            int add = 0;

            /*一次增加 DEFAULT_THREAD 个线程*/
            for (i = 0; i < pool->max_thr_num && add < DEFAULT_THREAD_VARY
                    && pool->live_thr_num < pool->max_thr_num; i++) {
                if (pool->threads[i] == 0 || !is_thread_alive(pool->threads[i])) {
                    pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);
                    add++;
                    pool->live_thr_num++;
                }
            }

            pthread_mutex_unlock(&(pool->lock));
        }

        /* 销毁多余的空闲线程 算法：忙线程X2 小于 存活的线程数 且 存活的线程数 大于 最小线程数时*/
        if ((busy_thr_num * 2) < live_thr_num  &&  live_thr_num > pool->min_thr_num) {

            /* 一次销毁DEFAULT_THREAD个线程, 隨機10個即可 */
            pthread_mutex_lock(&(pool->lock));
            pool->wait_exit_thr_num = DEFAULT_THREAD_VARY;      /* 要销毁的线程数 设置为10 */
            pthread_mutex_unlock(&(pool->lock));

            for (i = 0; i < DEFAULT_THREAD_VARY; i++) {
                /* 通知处在空闲状态的线程, 他们会自行终止*/
                pthread_cond_signal(&(pool->queue_not_empty));
            }
        }
    }

    return NULL;
}

threadpool.h：

#ifndef __THREADPOOL_H_
#define __THREADPOOL_H_

typedef struct threadpool_t threadpool_t;

/**
 * @function threadpool_create
 * @descCreates a threadpool_t object.
 * @param thr_num  thread num
 * @param max_thr_num  max thread size
 * @param queue_max_size   size of the queue.
 * @return a newly created thread pool or NULL
 */
threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);

/**
 * @function threadpool_add
 * @desc add a new task in the queue of a thread pool
 * @param pool     Thread pool to which add the task.
 * @param function Pointer to the function that will perform the task.
 * @param argument Argument to be passed to the function.
 * @return 0 if all goes well,else -1
 */
int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg);

/**
 * @function threadpool_destroy
 * @desc Stops and destroys a thread pool.
 * @param pool  Thread pool to destroy.
 * @return 0 if destory success else -1
 */
int threadpool_destroy(threadpool_t *pool);

/**
 * @desc get the thread num
 * @pool pool threadpool
 * @return # of the thread
 */
int threadpool_all_threadnum(threadpool_t *pool);

/**
 * desc get the busy thread num
 * @param pool threadpool
 * return # of the busy thread
 */
int threadpool_busy_threadnum(threadpool_t *pool);

#endif

threadpool.c：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "threadpool.h"

#define DEFAULT_TIME 10                 /*10s检测一次*/
#define MIN_WAIT_TASK_NUM 10            /*如果queue_size > MIN_WAIT_TASK_NUM 添加新的线程到线程池*/ 
#define DEFAULT_THREAD_VARY 10          /*每次创建和销毁线程的个数*/
#define true 1
#define false 0

typedef struct {
    void *(*function)(void *);          /* 函数指针，回调函数 */
    void *arg;                          /* 上面函数的参数 */
} threadpool_task_t;                    /* 各子线程任务结构体 */

/* 描述线程池相关信息 */
struct threadpool_t {
    pthread_mutex_t lock;               /* 用于锁住本结构体 */    
    pthread_mutex_t thread_counter;     /* 记录忙状态线程个数de琐 -- busy_thr_num */
    pthread_cond_t queue_not_full;      /* 当任务队列满时，添加任务的线程阻塞，等待此条件变量 */
    pthread_cond_t queue_not_empty;     /* 任务队列里不为空时，通知等待任务的线程 */

    pthread_t *threads;                 /* 存放线程池中每个线程的tid。数组 */
    pthread_t adjust_tid;               /* 存管理线程tid */
    threadpool_task_t *task_queue;      /* 任务队列 */

    int min_thr_num;                    /* 线程池最小线程数 */
    int max_thr_num;                    /* 线程池最大线程数 */
    int live_thr_num;                   /* 当前存活线程个数 */
    int busy_thr_num;                   /* 忙状态线程个数 */
    int wait_exit_thr_num;              /* 要销毁的线程个数 */

    int queue_front;                    /* task_queue队头下标 */
    int queue_rear;                     /* task_queue队尾下标 */
    int queue_size;                     /* task_queue队中实际任务数 */
    int queue_max_size;                 /* task_queue队列可容纳任务数上限 */

    int shutdown;                       /* 标志位，线程池使用状态，true或false */
};

/**
 * @function void *threadpool_thread(void *threadpool)
 * @desc the worker thread
 * @param threadpool the pool which own the thread
 */
void *threadpool_thread(void *threadpool);

/**
 * @function void *adjust_thread(void *threadpool);
 * @desc manager thread
 * @param threadpool the threadpool
 */
void *adjust_thread(void *threadpool);

/**
 * check a thread is alive
 */
int is_thread_alive(pthread_t tid);
int threadpool_free(threadpool_t *pool);

threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size)
{
    int i;
    threadpool_t *pool = NULL;
    do {
        if((pool = (threadpool_t *)malloc(sizeof(threadpool_t))) == NULL) {  
            printf("malloc threadpool fail");
            break;/*跳出do while*/
        }

        pool->min_thr_num = min_thr_num;
        pool->max_thr_num = max_thr_num;
        pool->busy_thr_num = 0;
        pool->live_thr_num = min_thr_num;               /* 活着的线程数 初值=最小线程数 */
        pool->queue_size = 0;                           /* 有0个产品 */
        pool->queue_max_size = queue_max_size;
        pool->queue_front = 0;
        pool->queue_rear = 0;
        pool->shutdown = false;                         /* 不关闭线程池 */

        /* 根据最大线程上限数， 给工作线程数组开辟空间, 并清零 */
        pool->threads = (pthread_t *)malloc(sizeof(pthread_t)*max_thr_num); 
        if (pool->threads == NULL) {
            printf("malloc threads fail");
            break;
        }
        memset(pool->threads, 0, sizeof(pthread_t)*max_thr_num);

        /* 队列开辟空间 */
        pool->task_queue = (threadpool_task_t *)malloc(sizeof(threadpool_task_t)*queue_max_size);
        if (pool->task_queue == NULL) {
            printf("malloc task_queue fail");
            break;
        }

        /* 初始化互斥琐、条件变量 */
        if (pthread_mutex_init(&(pool->lock), NULL) != 0
                || pthread_mutex_init(&(pool->thread_counter), NULL) != 0
                || pthread_cond_init(&(pool->queue_not_empty), NULL) != 0
                || pthread_cond_init(&(pool->queue_not_full), NULL) != 0)
        {
            printf("init the lock or cond fail");
            break;
        }

        /* 启动 min_thr_num 个 work thread */
        for (i = 0; i < min_thr_num; i++) {
            pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);/*pool指向当前线程池*/
            printf("start thread 0x%x...\n", (unsigned int)pool->threads[i]);
        }
        pthread_create(&(pool->adjust_tid), NULL, adjust_thread, (void *)pool);/* 启动管理者线程 */

        return pool;

    } while (0);

    threadpool_free(pool);      /* 前面代码调用失败时，释放poll存储空间 */

    return NULL;
}

/* 向线程池中 添加一个任务 */
int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg)
{
    pthread_mutex_lock(&(pool->lock));

    /* ==为真，队列已经满， 调wait阻塞 */
    while ((pool->queue_size == pool->queue_max_size) && (!pool->shutdown)) {
        pthread_cond_wait(&(pool->queue_not_full), &(pool->lock));
    }
    if (pool->shutdown) {
        pthread_mutex_unlock(&(pool->lock));
    }

    /* 清空 工作线程 调用的回调函数 的参数arg */
    if (pool->task_queue[pool->queue_rear].arg != NULL) {
        free(pool->task_queue[pool->queue_rear].arg);
        pool->task_queue[pool->queue_rear].arg = NULL;
    }
    /*添加任务到任务队列里*/
    pool->task_queue[pool->queue_rear].function = function;
    pool->task_queue[pool->queue_rear].arg = arg;
    pool->queue_rear = (pool->queue_rear + 1) % pool->queue_max_size;       /* 队尾指针移动, 模拟环形 */
    pool->queue_size++;

    /*添加完任务后，队列不为空，唤醒线程池中 等待处理任务的线程*/
    pthread_cond_signal(&(pool->queue_not_empty));
    pthread_mutex_unlock(&(pool->lock));

    return 0;
}

/* 线程池中各个工作线程 */
void *threadpool_thread(void *threadpool)
{
    threadpool_t *pool = (threadpool_t *)threadpool;
    threadpool_task_t task;

    while (true) {
        /* Lock must be taken to wait on conditional variable */
        /*刚创建出线程，等待任务队列里有任务，否则阻塞等待任务队列里有任务后再唤醒接收任务*/
        pthread_mutex_lock(&(pool->lock));

        /*queue_size == 0 说明没有任务，调 wait 阻塞在条件变量上, 若有任务，跳过该while*/
        while ((pool->queue_size == 0) && (!pool->shutdown)) {  
            printf("thread 0x%x is waiting\n", (unsigned int)pthread_self());
            pthread_cond_wait(&(pool->queue_not_empty), &(pool->lock));

            /*清除指定数目的空闲线程，如果要结束的线程个数大于0，结束线程*/
            if (pool->wait_exit_thr_num > 0) {
                pool->wait_exit_thr_num--;

                /*如果线程池里线程个数大于最小值时可以结束当前线程*/
                if (pool->live_thr_num > pool->min_thr_num) {
                    printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());
                    pool->live_thr_num--;
                    pthread_mutex_unlock(&(pool->lock));
                    pthread_exit(NULL);
                }
            }
        }

        /*如果指定了true，要关闭线程池里的每个线程，自行退出处理*/
        if (pool->shutdown) {
            pthread_mutex_unlock(&(pool->lock));
            printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());
            pthread_exit(NULL);     /* 线程自行结束 */
        }

        /*从任务队列里获取任务, 是一个出队操作*/
        task.function = pool->task_queue[pool->queue_front].function;
        task.arg = pool->task_queue[pool->queue_front].arg;

        pool->queue_front = (pool->queue_front + 1) % pool->queue_max_size;       /* 出队，模拟环形队列 */
        pool->queue_size--;

        /*通知可以有新的任务添加进来*/
        pthread_cond_broadcast(&(pool->queue_not_full));

        /*任务取出后，立即将 线程池琐 释放*/
        pthread_mutex_unlock(&(pool->lock));

        /*执行任务*/ 
        printf("thread 0x%x start working\n", (unsigned int)pthread_self());
        pthread_mutex_lock(&(pool->thread_counter));                            /*忙状态线程数变量琐*/
        pool->busy_thr_num++;                                                   /*忙状态线程数+1*/
        pthread_mutex_unlock(&(pool->thread_counter));
        (*(task.function))(task.arg);                                           /*执行回调函数任务*/
        //task.function(task.arg);                                              /*执行回调函数任务*/

        /*任务结束处理*/ 
        printf("thread 0x%x end working\n", (unsigned int)pthread_self());
        pthread_mutex_lock(&(pool->thread_counter));
        pool->busy_thr_num--;                                       /*处理掉一个任务，忙状态数线程数-1*/
        pthread_mutex_unlock(&(pool->thread_counter));
    }

    pthread_exit(NULL);
}

/* 管理线程 */
void *adjust_thread(void *threadpool)
{
    int i;
    threadpool_t *pool = (threadpool_t *)threadpool;
    while (!pool->shutdown) {

        sleep(DEFAULT_TIME);                                    /*定时 对线程池管理*/

        pthread_mutex_lock(&(pool->lock));
        int queue_size = pool->queue_size;                      /* 关注 任务数 */
        int live_thr_num = pool->live_thr_num;                  /* 存活 线程数 */
        pthread_mutex_unlock(&(pool->lock));

        pthread_mutex_lock(&(pool->thread_counter));
        int busy_thr_num = pool->busy_thr_num;                  /* 忙着的线程数 */
        pthread_mutex_unlock(&(pool->thread_counter));

        /* 创建新线程 算法： 任务数大于最小线程池个数, 且存活的线程数少于最大线程个数时 如：30>=10 && 40<100*/
        if (queue_size >= MIN_WAIT_TASK_NUM && live_thr_num < pool->max_thr_num) {
            pthread_mutex_lock(&(pool->lock));  
            int add = 0;

            /*一次增加 DEFAULT_THREAD 个线程*/
            for (i = 0; i < pool->max_thr_num && add < DEFAULT_THREAD_VARY
                    && pool->live_thr_num < pool->max_thr_num; i++) {
                if (pool->threads[i] == 0 || !is_thread_alive(pool->threads[i])) {
                    pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);
                    add++;
                    pool->live_thr_num++;
                }
            }

            pthread_mutex_unlock(&(pool->lock));
        }

        /* 销毁多余的空闲线程 算法：忙线程X2 小于 存活的线程数 且 存活的线程数 大于 最小线程数时*/
        if ((busy_thr_num * 2) < live_thr_num  &&  live_thr_num > pool->min_thr_num) {

            /* 一次销毁DEFAULT_THREAD个线程, 隨機10個即可 */
            pthread_mutex_lock(&(pool->lock));
            pool->wait_exit_thr_num = DEFAULT_THREAD_VARY;      /* 要销毁的线程数 设置为10 */
            pthread_mutex_unlock(&(pool->lock));

            for (i = 0; i < DEFAULT_THREAD_VARY; i++) {
                /* 通知处在空闲状态的线程, 他们会自行终止*/
                pthread_cond_signal(&(pool->queue_not_empty));
            }
        }
    }

    return NULL;
}

int threadpool_destroy(threadpool_t *pool)
{
    int i;
    if (pool == NULL) {
        return -1;
    }
    pool->shutdown = true;

    /*先销毁管理线程*/
    pthread_join(pool->adjust_tid, NULL);

    for (i = 0; i < pool->live_thr_num; i++) {
        /*通知所有的空闲线程*/
        pthread_cond_broadcast(&(pool->queue_not_empty));
    }
    for (i = 0; i < pool->live_thr_num; i++) {
        pthread_join(pool->threads[i], NULL);
    }
    threadpool_free(pool);

    return 0;
}

int threadpool_free(threadpool_t *pool)
{
    if (pool == NULL) {
        return -1;
    }

    if (pool->task_queue) {
        free(pool->task_queue);
    }
    if (pool->threads) {
        free(pool->threads);
        pthread_mutex_lock(&(pool->lock));
        pthread_mutex_destroy(&(pool->lock));
        pthread_mutex_lock(&(pool->thread_counter));
        pthread_mutex_destroy(&(pool->thread_counter));
        pthread_cond_destroy(&(pool->queue_not_empty));
        pthread_cond_destroy(&(pool->queue_not_full));
    }
    free(pool);
    pool = NULL;

    return 0;
}

int threadpool_all_threadnum(threadpool_t *pool)
{
    int all_threadnum = -1;
    pthread_mutex_lock(&(pool->lock));
    all_threadnum = pool->live_thr_num;
    pthread_mutex_unlock(&(pool->lock));
    return all_threadnum;
}

int threadpool_busy_threadnum(threadpool_t *pool)
{
    int busy_threadnum = -1;
    pthread_mutex_lock(&(pool->thread_counter));
    busy_threadnum = pool->busy_thr_num;
    pthread_mutex_unlock(&(pool->thread_counter));
    return busy_threadnum;
}

int is_thread_alive(pthread_t tid)
{
    int kill_rc = pthread_kill(tid, 0);     //发0号信号，测试线程是否存活
    if (kill_rc == ESRCH) {
        return false;
    }

    return true;
}

/*测试*/ 

#if 1
/* 线程池中的线程，模拟处理业务 */
void *process(void *arg)
{
    printf("thread 0x%x working on task %d\n ",(unsigned int)pthread_self(),*(int *)arg);
    sleep(1);
    printf("task %d is end\n",*(int *)arg);

    return NULL;
}
int main(void)
{
    /*threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);*/

    threadpool_t *thp = threadpool_create(3,100,100);/*创建线程池，池里最小3个线程，最大100，队列最大100*/
    printf("pool inited");

    //int *num = (int *)malloc(sizeof(int)*20);
    int num[20], i;
    for (i = 0; i < 20; i++) {
        num[i]=i;
        printf("add task %d\n",i);
        threadpool_add(thp, process, (void*)&num[i]);     /* 向线程池中添加任务 */
    }
    sleep(10);                                          /* 等子线程完成任务 */
    threadpool_destroy(thp);

    return 0;
}

#endif

makefile：

src = $(wildcard *.c)
targets = $(patsubst %.c, %, $(src))

CC = gcc
CFLAGS = -lpthread -Wall -g 

all:$(targets)

$(targets):%:%.c
	$(CC) $< -o $@ $(CFLAGS)

.PHONY:clean all
clean:
	-rm -rf $(targets)