第184页 第18章 多线程服务器端的实现

多进程模型的缺点：
    1.创建进程、Context Switching开销大；
    2.进程间通信，需要特殊IPC技术。

线程编程介绍：http://book.douban.com/annotation/34642229/

线程安全函数：Linnux平台在定义非线程安全函数同时提供了具有相同功能额线程安全函数；线程安全函数后缀通常为_t Or 在编译程序时使用宏选项(-D_REENTRANT)。
/*************************************************************************
	> File Name: thread_test.c
	> Author: xjhznick
	> Mail: xjhznick@gmail.com 
	> Created Time: 2015年04月03日 星期五 15时15分58秒
  > Description:
 ************************************************************************/

#include<stdio.h>
#include<pthread.h>
#include<unistd.h>
#include<stdlib.h>

#define THREAD_NUM 100

void * thread_inc(void *arg);
void * thread_dec(void *arg);

long long num = 0;

int main(int argc, char *argv[])
{
	pthread_t thread_id[THREAD_NUM];
	int i;

	printf("sizeof(long long) = %lu\n", sizeof(long long));
	for(i=0; i<THREAD_NUM; i++){
		if(i%2){
			pthread_create(&(thread_id[i]), NULL, thread_inc, NULL);
		}else{
			pthread_create(&(thread_id[i]), NULL, thread_dec, NULL);
		}
		//pthread_join(thread_id[i], NULL); //The result is OK.
	}
	for(i=0; i<THREAD_NUM; i++){
		pthread_join(thread_id[i], NULL);
	}
	
	printf("Result = %lld\n", num);
	return 0;	
}

void *thread_inc(void *arg)
{
	int i;
	for(i=0; i<50000000; i++){
		num += 1;
	}
	return NULL;
}
void *thread_dec(void *arg)
{
	int i;
	for(i=0; i<50000000; i++){
		num -= 1;
	}
	return NULL;
}
$ gcc pthread_test.c -D_REENTRANT -lpthread
$ ./a.out 
sizeof(long long) = 8
Result = -1437615
-------------------------------------------------------------------------------------------------------
需要考虑进行同步的情况：
    1.同时访问同一内存空间；
    2.需要指定访问同一内存空间的线程执行顺序的情况
例如将生活中的厕所当作临界区对待，其使用规则与程序中互斥量(一个坑位) 信号量(n个坑位)访问临界区规则完全一样。
/*************************************************************************
	> File Name: thread_mutex_test.c
	> Author: xjhznick
	> Mail: xjhznick@gmail.com 
	> Created Time: 2015年04月03日 星期五 15时45分58秒
  > Description:
 ************************************************************************/

#include<stdio.h>
#include<pthread.h>
#include<unistd.h>
#include<stdlib.h>

#define THREAD_NUM 30

void * thread_inc(void *arg);
void * thread_dec(void *arg);

long long num = 0;
pthread_mutex_t mutex;

int main(int argc, char *argv[])
{
	pthread_t thread_id[THREAD_NUM];
	int i;

	pthread_mutex_init(&mutex,NULL);

	printf("sizeof(long long) = %lu\n", sizeof(long long));
	for(i=0; i<THREAD_NUM; i++){
		if(i%2){
			pthread_create(&(thread_id[i]), NULL, thread_inc, NULL);
		}else{
			pthread_create(&(thread_id[i]), NULL, thread_dec, NULL);
		}
		//pthread_join(thread_id[i], NULL); //The result is OK.
	}
	for(i=0; i<THREAD_NUM; i++){
		pthread_join(thread_id[i], NULL);
	}
	
	pthread_mutex_destroy(&mutex);

	printf("Result = %lld\n", num);
	return 0;	
}

void *thread_inc(void *arg)
{
	int i;
	pthread_mutex_lock(&mutex);
	for(i=0; i<50000000; i++){
		num += 1;
	}
	pthread_mutex_unlock(&mutex);
	return NULL;
}
//两个函数临界区划分范围不同，thread_inc划分范围大，但是其它线程等待时间长；thread_dec划分范围小，但是lock、unlock函数调用那个次数多----需要折中
void *thread_dec(void *arg)
{
	int i;
	for(i=0; i<50000000; i++){
		pthread_mutex_lock(&mutex);
		num -= 1;
		pthread_mutex_unlock(&mutex);
	}
	return NULL;
}
$ gcc pthread_mutex_test.c -D_REENTRANT -lpthread
$ ./a.out 
sizeof(long long) = 8
Result = 0
-------------------------------------------------------------------------------------------------------
/*************************************************************************
	> File Name: chat_pthread_client.c
	> Author: xjhznick
	> Mail: xjhznick@gmail.com 
	> Created Time: 2015年04月03日 星期五 16时30分34秒
  > Description:
 ************************************************************************/

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<pthread.h>

#define BUFF_SIZE 100 
#define NAME_SIZE 20 

void error_handling(char *message);
void *send_msg(void *msg);
void *recv_msg(void *msg);
//Global data section
char name[NAME_SIZE] = "[DEFAULT]";
char msg[BUFF_SIZE];

int main(int argc, char *argv[])
{
	int sock_server;
	struct sockaddr_in addr_server;
	pthread_t pthread_id_send, pthread_id_recv;	
	void *thread_ret;

	if(argc!=4){ //命令行中启动服务程序仅限一个参数：端口号
		printf("Usage : %s <IP> <port> <name>\n", argv[0]);
		exit(1);
	}
	sprintf(name, "[%s]", argv[3]);

	//调用socket函数创建套接字
	sock_server = socket(PF_INET, SOCK_STREAM, 0);
	if(-1 == sock_server){
		error_handling("socket() error.");
	}

	memset(&addr_server, 0, sizeof(addr_server));
	addr_server.sin_family = AF_INET;
	addr_server.sin_addr.s_addr = inet_addr(argv[1]);
	addr_server.sin_port = htons(atoi(argv[2]));
	//绑定 
	if(-1 == connect(sock_server, (struct sockaddr*)&addr_server, sizeof(addr_server))){
		error_handling("Error connect()");
	}
	
	pthread_create(&pthread_id_send, NULL, send_msg, (void*)&sock_server);
	pthread_create(&pthread_id_recv, NULL, recv_msg, (void*)&sock_server);
	pthread_join(pthread_id_send, &thread_ret);
	pthread_join(pthread_id_recv, &thread_ret);

	fputs("End of Client!\n", stderr);
	//断开连接，关闭套接字
	close(sock_server);
	return 0;
}

void error_handling(char *message)
{
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(EXIT_FAILURE);
}
void *send_msg(void *arg)
{
	int sock = *((int *)arg);
	char name_msg[NAME_SIZE+BUFF_SIZE];
	while(1){
		//puts("Input Message(Q quit):");
		fgets(msg, BUFF_SIZE, stdin);
		if( !strcmp(msg, "q\n") || !strcmp(msg, "Q\n") ){
			fputs("Quit!\n", stderr);
			close(sock);
			exit(0);
		}
		sprintf(name_msg, "%s %s", name, msg);
		write(sock, name_msg, strlen(name_msg));
	//	fputs("Sent a message!\n", stderr);
	}
	return NULL;
}
void *recv_msg(void *arg)
{

	int sock = *((int *)arg);
	char name_msg[NAME_SIZE+BUFF_SIZE];
	int str_len;
	while(1){
		str_len = read(sock, name_msg, NAME_SIZE+BUFF_SIZE-1);
		if(str_len < 0) return (void*)-1;
		name_msg[str_len] = 0;
		fputs(name_msg, stdout);
	}
	return NULL;
}
/*************************************************************************
	> File Name: chat_pthread_server.c
	> Author: xjhznick
	> Mail: xjhznick@gmail.com 
	> Created Time: 2015年04月03日 星期五 15时58分53秒
  > Description:基于多线程的聊天程序--服务器端
 ************************************************************************/

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<pthread.h>

#define BUFF_SIZE 100 
#define CLIENT_MAX 256 

void error_handling(char *message);
void *client_handler(void *arg);
void send_msg(char *msg, int len);

int count_client = 0;
int socks_client[CLIENT_MAX];
pthread_mutex_t mutex;

int main(int argc, char *argv[])
{
	int sock_server;
	int sock_client;

	struct sockaddr_in addr_server;
	struct sockaddr_in addr_client;
	socklen_t size_addr_client;

	pthread_t pthread_id;	

	if(argc!=2){ //命令行中启动服务程序仅限一个参数：端口号
		printf("Usage : %s <port>\n", argv[0]);
		exit(1);
	}
	
	pthread_mutex_init(&mutex, NULL);
	//调用socket函数创建套接字
	sock_server = socket(PF_INET, SOCK_STREAM, 0);
	if(-1 == sock_server){
		error_handling("socket() error.");
	}

	memset(&addr_server, 0, sizeof(addr_server));
	addr_server.sin_family = AF_INET;
	addr_server.sin_addr.s_addr = htonl(INADDR_ANY);
	addr_server.sin_port = htons(atoi(argv[1]));
	
	//调用bind函数分配IP地址和端口号
	if( -1 == bind( sock_server, (struct sockaddr*)&addr_server, 
				sizeof(addr_server)) ){
		error_handling("bind() error");
	}

	//监听端口的连接请求,连接请求等待队列size为5
	if( -1 == listen(sock_server, 5) ){
		error_handling("listen() error");
	}

	//
	while(1){
		size_addr_client = sizeof(addr_client);
		sock_client = accept( sock_server, (struct sockaddr*)&addr_client, &size_addr_client);

		pthread_mutex_lock(&mutex);
		socks_client[count_client++] = sock_client;//Lock 访问公共代码区
		pthread_mutex_unlock(&mutex);

		pthread_create(&pthread_id, NULL, client_handler, (void *)&sock_client);
		pthread_detach(pthread_id);//销毁线程
		printf("Client IP:%s \n", inet_ntoa(addr_client.sin_addr));

	}//end of while 

	//断开连接，关闭套接字
	close(sock_server);
	pthread_mutex_destroy(&mutex);
	return 0;
}

void error_handling(char *message)
{
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(EXIT_FAILURE);
}
void *client_handler(void *arg)
{
	int sock_client = *((int *)arg);
	int str_len = 0, i;
	char msg[BUFF_SIZE];

	while((str_len = read(sock_client, msg, BUFF_SIZE-1)) > 0){
		//msg[str_len] = 0;
		//printf("Received a messgae: %s", msg);
		send_msg(msg, str_len);
	}

	pthread_mutex_lock(&mutex);
	for(i=0; i<count_client; i++){//remove disconnencted client
		if(sock_client == socks_client[i]){
			while(i++ <= count_client-1){
				socks_client[i] = socks_client[i+1];
			}
			break;
		}
	}
	count_client--;
	pthread_mutex_unlock(&mutex);
	close(sock_client);

	return NULL;
}
void send_msg(char *msg, int len)//send message to all clients
{
	int i;
	pthread_mutex_lock(&mutex);
	for(i=0; i<count_client; i++){
		write(socks_client[i], msg, len);
	}
	pthread_mutex_unlock(&mutex);
}