recvfd.c

unix环境高级编程的源代码

#include    <sys/types.h>
#include    <stropts.h>
#include    "ourhdr.h"

/* Receive a file descriptor from another process (a server).
 * In addition, any data received from the server is passed
 * to (*userfunc)(STDERR_FILENO, buf, nbytes).  We have a
 * 2-byte protocol for receiving the fd from send_fd(). */

int
recv_fd(int servfd, ssize_t (*userfunc)(int, const void *, size_t))
{
    int                    newfd, nread, flag, status;
    char                *ptr, buf[MAXLINE];
    struct strbuf        dat;
    struct strrecvfd    recvfd;

    status = -1;
    for ( ; ; ) {
        dat.buf = buf;
        dat.maxlen = MAXLINE;
        flag = 0;
        if (getmsg(servfd, NULL, &dat, &flag) < 0)
            err_sys("getmsg error");
        nread = dat.len;
        if (nread == 0) {
            err_ret("connection closed by server");
            return(-1);
        }
            /* See if this is the final data with null & status.
               Null must be next to last byte of buffer, status
               byte is last byte.  Zero status means there must
               be a file descriptor to receive. */
        for (ptr = buf; ptr < &buf[nread]; ) {
            if (*ptr++ == 0) {
                if (ptr != &buf[nread-1])
                    err_dump("message format error");
                 status = *ptr & 255;
                 if (status == 0) {
                    if (ioctl(servfd, I_RECVFD, &recvfd) < 0)
                        return(-1);
                    newfd = recvfd.fd;    /* new descriptor */
                } else
                    newfd = -status;
                nread -= 2;
            }
        }
        if (nread > 0)
            if ((*userfunc)(STDERR_FILENO, buf, nread) != nread)
                return(-1);

        if (status >= 0)    /* final data has arrived */
            return(newfd);    /* descriptor, or -status */
    }
}