source: rtems/cpukit/libnetworking/rtems/rtems_select.c @ f7ceeacf

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <string.h>
#include <stdarg.h>
/* #include <stdlib.h> */
#include <stdio.h>

#include <rtems.h>
#include <rtems/libio.h>
#include <rtems/error.h>
#include <rtems/rtems_bsdnet.h>

#include <errno.h>
#include <sys/fcntl.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/proc.h>
#include <sys/filio.h>

#include <net/if.h>
#include <net/route.h>

/*
 *********************************************************************
 *            RTEMS implementation of select() system call           *
 *********************************************************************
 */

/*
 * This implementation is quite restricted:
 *      Works on sockets only -- no support for other devices!
 *      A given socket can be in a read-select or a read/recv* by only
 *              one task at a time.
 *      A given socket can be in a write-select or a write/send* by only
 *              one task at a time.
 *
 * NOTE - select() is a very expensive system call.  It should be avoided
 *        if at all possible.  In many cases, rewriting the application
 *        to use multiple tasks (one per socket) is a better solution.
 */

static __inline int imin(int a, int b) { return (a < b ? a : b); }
struct socket *rtems_bsdnet_fdToSocket(int fd);

static int
socket_select (struct socket *so, int which, rtems_id tid)
{
        switch (which) {

        case FREAD:
                if (soreadable(so))
                        return (1);
                so->so_rcv.sb_flags |= SB_WAIT;
                so->so_rcv.sb_sel.si_pid = tid;
                break;

        case FWRITE:
                if (sowriteable(so))
                        return (1);
                so->so_snd.sb_flags |= SB_WAIT;
                so->so_snd.sb_sel.si_pid = tid;
                break;

        case 0:
                if (so->so_oobmark || (so->so_state & SS_RCVATMARK))
                        return (1);
                so->so_rcv.sb_sel.si_pid = tid;
                break;
        }
        return (0);
}

static int
selscan (rtems_id tid, fd_mask **ibits, fd_mask **obits, int nfd, int *retval)
{
        struct socket *so;
        int msk, i, fd;
        fd_mask bits, bit;
        int n = 0;
        static int flag[3] = { FREAD, FWRITE, 0 };

        for (msk = 0; msk < 3; msk++) {
                if (ibits[msk] == NULL)
                        continue;
                for (i = 0; i < nfd; i += NFDBITS) {
                        bits = ibits[msk][i/NFDBITS];
                        for (fd = i, bit = 1 ; bits && (fd < nfd) ; fd++, bit <<= 1) {
                                if ((bits & bit) == 0)
                                        continue;
                                bits &= ~bit;
                                so = rtems_bsdnet_fdToSocket (fd);
                                if (so == NULL)
                                        return (EBADF);
                                if (socket_select (so, flag[msk], tid)) {
                                        obits[msk][fd/NFDBITS] |=
                                                        (1 << (fd % NFDBITS));
                                        n++;
                                }
                        }
                }
        }
        *retval = n;
        return (0);
}

int
select (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *tv)
{
        fd_mask *ibits[3], *obits[3];
        fd_set ob[3];
        int error, timo;
        int retval = 0;
        rtems_id tid;
        rtems_interval then = 0, now;
        rtems_event_set events;

        if (nfds < 0)
                return (EINVAL);
        if (tv) {
                timo = tv->tv_sec * hz + tv->tv_usec / tick;
                if (timo == 0)
                        timo = 1;
                then = rtems_clock_get_ticks_since_boot();
        }
        else {
                timo = 0;
        }

#define getbits(name,i) if (name) { \
                ibits[i] = &name->fds_bits[0]; \
                obits[i] = &ob[i].fds_bits[0]; \
                FD_ZERO(&ob[i]); \
        } \
        else ibits[i] = NULL
        getbits (readfds, 0);
        getbits (writefds, 1);
        getbits (exceptfds, 2);
#undef getbits

        rtems_task_ident (RTEMS_SELF, 0, &tid);
        rtems_event_receive (SBWAIT_EVENT, RTEMS_EVENT_ANY | RTEMS_NO_WAIT, RTEMS_NO_TIMEOUT, &events);
        for (;;) {
                rtems_bsdnet_semaphore_obtain ();
                error = selscan(tid, ibits, obits, nfds, &retval);
                rtems_bsdnet_semaphore_release ();
                if (error || retval)
                        break;
                if (timo) {
                        now = rtems_clock_get_ticks_since_boot();
                        timo -= now - then;
                        if (timo <= 0)
                                break;
                        then = now;
                }
                rtems_event_receive (SBWAIT_EVENT, RTEMS_EVENT_ANY | RTEMS_WAIT, timo, &events);
        }

#define putbits(name,i) if (name) *name = ob[i]
        putbits (readfds, 0);
        putbits (writefds, 1);
        putbits (exceptfds, 2);
#undef putbits
        if (error) {
                errno = error;
                retval = -1;
        }
        return (retval);
}