#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#define BUF_SIZE 1024
#define OPSZ 4
void error_handling(char *message);
int calculate(int opnum, int opnds[], char oprator);

int main(int argc, char *argv[])
{
	int serv_sock,clnt_sock;
	char opinfo[BUF_SIZE];
	int result,opnd_cnt,i;
	int recv_cnt,recv_len;
	struct sockaddr_in serv_adr,clnt_adr;
	socklen_t clnt_adr_sz;
	if (argc != 2){
		printf("Usage : %s <port>\n", argv[0]);
		exit(1);
	}

	serv_sock = socket(PF_INET,SOCK_STREAM,0);
	if(serv_sock == -1)
		error_handling("socket() error");
	
	memset(&serv_adr,0,sizeof(serv_adr));
	serv_adr.sin_family = AF_INET;
	serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
	serv_adr.sin_port = htons(atoi(argv[1]));

	if(bind(serv_sock,(struct sockaddr*)&serv_adr,sizeof(serv_adr)) == -1)
		error_handling("bind() error");

	if(listen(hServSock,5) == -1)
		error_handling("listen() error");

	clnt_adr_sz = sizeof(clntAdr);

	for (i=0;i<5;i++)    // 为了接收5个客户端
	{
		opnd_cnt = 0;
		clnt_sock = accept(serv_sock,(struct sockaddr*)&clnt_adr,&clnt_adr_sz);
		read(clnt_sock,&opnd_cnt,1);   // 首先接收 待算数个数
		
		recv_len = 0;
		while ((opnd_cnt*OPSZ+1)>recv_len)   // 根据 待算数个数 接收 待算数
		{
			recv_cnt = read(clnt_sock, &opinfo[recv_len], BUF_SIZE-1);
			recv_len += recv_cnt;
		}
		result = calculate(opnd_cnt, (int*)opinfo, opinfo[recv_len-1]);   // 调用calculate
		write(clnt_sock,(char*)&result,sizeof(result));   // 向客户端返回运算结果
		close(clnt_sock);
	}
	close(serv_sock);
	return 0;
}

int calculate(int opum, int opnds[], char op)
{
	int result = opnds[0],i;
	switch(op)
	{
	case '+':
		for(i=1;i<opnum;i++) result += opnds[i];
		break;
	case '-':
		for(i=1;i<opnum;i++) result -= opnds[i];
		break;
	case '*':
		for(i=1;i<opnum;i++) result *= opnds[i];
		break;
	}
	return result
}

void error_handling(char *message)
{
	fputs(message,stderr);
	fputc('\n',stderr);
	exit(1);
}
