example25.c

LinuxNetProgramming Linux网络编程基础实例

#include	<stdio.h>
#include	<sys/msg.h>
#include	<sys/ipc.h>
#include	<sys/types.h>
#include 	<errno.h>
#include	<string.h>

#define	MAXMESGDATA	1000
#define	SVMSG_MODE	777

struct mymesg {
    long	mesg_len;	/* #bytes in mesg_data, can be 0 */
    long	mesg_type;	/* message type, must be > 0 */
    char	mesg_data[MAXMESGDATA];
};

size_t   msg_send(int, struct mymesg *);
size_t   mesg_recv(int id, struct mymesg *mptr);
int
main()
{
	int	msgid;
	FILE	*fp;
	char	*ptr;
	pid_t	pid;
	ssize_t	n;
	struct mymesg mesg;

	msgid = msgget(1234, SVMSG_MODE | IPC_CREAT); /*、以1234为key创建一个消息队列 */

	for( ; ; ) {	/*循环从消息队列中读取客户请求 */
		mesg.mesg_type = 1;
		if ((n = mesg_recv(msgid, &mesg)) == 0) {
			printf("pathname missing");
			continue;
		}
		mesg.mesg_data[n] = '\0';	/*将消息的数据段格式化成以空字符结束的字符串 */
		if ((ptr = strchr(mesg.mesg_data, ' ')) == NULL) {
			printf("bogus request: %s", mesg.mesg_data);
			continue;
		}
		*ptr++ = 0;
		pid = atol(mesg.mesg_data); /*获得发送消息的客户进程的进程号 */
		mesg.mesg_type = pid;	
		if ((fp = fopen(ptr, "r")) == NULL) { /*打开所请求文件来读 */
			snprintf(mesg.mesg_data + n, sizeof(mesg.mesg_data) -n, ":can't open, %s\n", strerror(errno));
			mesg.mesg_len = strlen(ptr);
			memmove(mesg.mesg_data, ptr, mesg.mesg_len);
			msg_send(msgid, &mesg);	/*将文件内容写回消息队列 */
		}
		else {	/*若文件不存在，则将客户的请求消息内容再写回消息队列 */
			while(fgets(mesg.mesg_data, MAXMESGDATA, fp) != NULL) {
				mesg.mesg_len = strlen(mesg.mesg_data);
				msg_send(msgid, &mesg);
			}
			fclose(fp);
		}
		mesg.mesg_len = 0;
		msg_send(msgid, &mesg);
	}
	exit(0);
}

size_t
msg_send(int id, struct mymesg *mptr)
{
	return(msgsnd(id, &(mptr->mesg_type), mptr->mesg_len, 0));
}
/* end mesg_send */
size_t
mesg_recv(int id, struct mymesg *mptr)
{
	ssize_t	n;

	n = msgrcv(id, &(mptr->mesg_type), MAXMESGDATA, mptr->mesg_type, 0);
	mptr->mesg_len = n;		/* return #bytes of data */

	return(n);				/* -1 on error, 0 at EOF, else >0 */
}