qcore_unix.cpp

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#include "qcore_unix_p.h"
#include "qelapsedtimer.h"

#ifdef Q_OS_NACL
#elif !defined (Q_OS_VXWORKS)
# if !defined(Q_OS_HPUX) || defined(__ia64)
#  include <sys/select.h>
# endif
#  include <sys/time.h>
#else
#  include <selectLib.h>
#endif

#include <stdlib.h>

#ifdef Q_OS_MAC
#include <mach/mach_time.h>
#endif

QT_BEGIN_NAMESPACE

static inline bool time_update(struct timeval *tv, const struct timeval &start,
                               const struct timeval &timeout)
{
    // 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;
}

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

QT_END_NAMESPACE