read_fd.c

Unix网络编程 基于Socket的网络编程

/* include read_fd */
#include	"unp.h"

ssize_t
read_fd(int fd, void *ptr, size_t nbytes, int *recvfd)
{
	struct msghdr	msg;
	struct iovec	iov[1];
	ssize_t			n;
	int				newfd;

#ifdef	HAVE_MSGHDR_MSG_CONTROL
	union {
	  struct cmsghdr	cm;
	  char				control[CMSG_SPACE(sizeof(int))];
	} control_un;
	struct cmsghdr	*cmptr;

	msg.msg_control = control_un.control;
	msg.msg_controllen = sizeof(control_un.control);
#else
	msg.msg_accrights = (caddr_t) &newfd;
	msg.msg_accrightslen = sizeof(int);
#endif

	msg.msg_name = NULL;
	msg.msg_namelen = 0;

	iov[0].iov_base = ptr;
	iov[0].iov_len = nbytes;
	msg.msg_iov = iov;
	msg.msg_iovlen = 1;

	if ( (n = recvmsg(fd, &msg, 0)) <= 0)
		return(n);

#ifdef	HAVE_MSGHDR_MSG_CONTROL
	if ( (cmptr = CMSG_FIRSTHDR(&msg)) != NULL &&
	    cmptr->cmsg_len == CMSG_LEN(sizeof(int))) {
		if (cmptr->cmsg_level != SOL_SOCKET)
			err_quit("control level != SOL_SOCKET");
		if (cmptr->cmsg_type != SCM_RIGHTS)
			err_quit("control type != SCM_RIGHTS");
		*recvfd = *((int *) CMSG_DATA(cmptr));
	} else
		*recvfd = -1;		/* descriptor was not passed */
#else
/* *INDENT-OFF* */
	if (msg.msg_accrightslen == sizeof(int))
		*recvfd = newfd;
	else
		*recvfd = -1;		/* descriptor was not passed */
/* *INDENT-ON* */
#endif

	return(n);
}
/* end read_fd */

ssize_t
Read_fd(int fd, void *ptr, size_t nbytes, int *recvfd)
{
	ssize_t		n;

	if ( (n = read_fd(fd, ptr, nbytes, recvfd)) < 0)
		err_sys("read_fd error");

	return(n);
}