qcore_unix.cpp File Reference

#include "qcore_unix_p.h"
#include "qelapsedtimer.h"
#include <sys/select.h>
#include <sys/time.h>
#include <stdlib.h>
#include <mach/mach_time.h>

Go to the source code of this file.

Functions
int	qt_safe_select (int nfds, fd_set *fdread, fd_set *fdwrite, fd_set *fdexcept, const struct timeval *orig_timeout)
static bool	time_update (struct timeval *tv, const struct timeval &start, const struct timeval &timeout)

Function Documentation

qt_safe_select()

int qt_safe_select	(	int	nfds,
		fd_set *	fdread,
		fd_set *	fdwrite,
		fd_set *	fdexcept,
		const struct timeval *	orig_timeout
	)

Definition at line 73 of file qcore_unix.cpp.

Referenced by QNativeSocketEnginePrivate::nativeSelect(), SelectWorker::run(), QEventDispatcherUNIX::select(), and select_msecs().

{
    if (!orig_timeout) {
        // no timeout -> block forever
        register int ret;
        EINTR_LOOP(ret, select(nfds, fdread, fdwrite, fdexcept, 0));
        return ret;
    }

    timeval start = qt_gettime();
    timeval timeout = *orig_timeout;

    // loop and recalculate the timeout as needed
    int ret;
    forever {
        ret = ::select(nfds, fdread, fdwrite, fdexcept, &timeout);
        if (ret != -1 || errno != EINTR)
            return ret;

        // recalculate the timeout
        if (!time_update(&timeout, start, *orig_timeout)) {
            // timeout during update
            // or clock reset, fake timeout error
            return 0;
        }
    }
}

time_update()

static bool time_update ( struct timeval *  tv, const struct timeval &  start, const struct timeval &  timeout  )

inlinestatic

Definition at line 63 of file qcore_unix.cpp.

Referenced by qt_safe_select().

{
    // clock source is (hopefully) monotonic, so we can recalculate how much timeout is left;
    // if it isn't monotonic, we'll simply hope that it hasn't jumped, because we have no alternative
    struct timeval now = qt_gettime();
    *tv = timeout + start - now;
    return tv->tv_sec >= 0;
}