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41
42 #include "qcore_unix_p.h"
43 #include "qelapsedtimer.h"
44
45 #ifdef Q_OS_NACL
46 #elif !defined (Q_OS_VXWORKS)
47 # if !defined(Q_OS_HPUX) || defined(__ia64)
48 # include <sys/select.h>
49 # endif
50 # include <sys/time.h>
51 #else
52 # include <selectLib.h>
53 #endif
54
55 #include <stdlib.h>
56
57 #ifdef Q_OS_MAC
58 #include <mach/mach_time.h>
59 #endif
60
61 QT_BEGIN_NAMESPACE
62
time_update(struct timeval * tv,const struct timeval & start,const struct timeval & timeout)63 static inline bool time_update(struct timeval *tv, const struct timeval &start,
64 const struct timeval &timeout)
65 {
66 // clock source is (hopefully) monotonic, so we can recalculate how much timeout is left;
67 // if it isn't monotonic, we'll simply hope that it hasn't jumped, because we have no alternative
68 struct timeval now = qt_gettime();
69 *tv = timeout + start - now;
70 return tv->tv_sec >= 0;
71 }
72
qt_safe_select(int nfds,fd_set * fdread,fd_set * fdwrite,fd_set * fdexcept,const struct timeval * orig_timeout)73 int qt_safe_select(int nfds, fd_set *fdread, fd_set *fdwrite, fd_set *fdexcept,
74 const struct timeval *orig_timeout)
75 {
76 if (!orig_timeout) {
77 // no timeout -> block forever
78 int ret;
79 EINTR_LOOP(ret, select(nfds, fdread, fdwrite, fdexcept, 0));
80 return ret;
81 }
82
83 timeval start = qt_gettime();
84 timeval timeout = *orig_timeout;
85
86 // loop and recalculate the timeout as needed
87 int ret;
88 forever {
89 ret = ::select(nfds, fdread, fdwrite, fdexcept, &timeout);
90 if (ret != -1 || errno != EINTR)
91 return ret;
92
93 // recalculate the timeout
94 if (!time_update(&timeout, start, *orig_timeout)) {
95 // timeout during update
96 // or clock reset, fake timeout error
97 return 0;
98 }
99 }
100 }
101
102 QT_END_NAMESPACE
103