1/****************************************************************************
2**
3** Copyright (C) 2016 The Qt Company Ltd.
4** Copyright (C) 2016 Intel Corporation.
5** Contact: https://www.qt.io/licensing/
6**
7** This file is part of the QtCore module of the Qt Toolkit.
8**
9** $QT_BEGIN_LICENSE:LGPL$
10** Commercial License Usage
11** Licensees holding valid commercial Qt licenses may use this file in
12** accordance with the commercial license agreement provided with the
13** Software or, alternatively, in accordance with the terms contained in
14** a written agreement between you and The Qt Company. For licensing terms
15** and conditions see https://www.qt.io/terms-conditions. For further
16** information use the contact form at https://www.qt.io/contact-us.
17**
18** GNU Lesser General Public License Usage
19** Alternatively, this file may be used under the terms of the GNU Lesser
20** General Public License version 3 as published by the Free Software
21** Foundation and appearing in the file LICENSE.LGPL3 included in the
22** packaging of this file. Please review the following information to
23** ensure the GNU Lesser General Public License version 3 requirements
24** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
25**
26** GNU General Public License Usage
27** Alternatively, this file may be used under the terms of the GNU
28** General Public License version 2.0 or (at your option) the GNU General
29** Public license version 3 or any later version approved by the KDE Free
30** Qt Foundation. The licenses are as published by the Free Software
31** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
32** included in the packaging of this file. Please review the following
33** information to ensure the GNU General Public License requirements will
34** be met: https://www.gnu.org/licenses/gpl-2.0.html and
35** https://www.gnu.org/licenses/gpl-3.0.html.
36**
37** $QT_END_LICENSE$
38**
39****************************************************************************/
40
41#include <QtCore/private/qglobal_p.h>
42#include "qcore_unix_p.h"
43#include "qelapsedtimer.h"
44
45#include <stdlib.h>
46
47#ifdef __GLIBC__
48# include <sys/syscall.h>
49# include <pthread.h>
50# include <unistd.h>
51#endif
52
53#ifdef Q_OS_MAC
54#include <mach/mach_time.h>
55#endif
56
57QT_BEGIN_NAMESPACE
58
59QByteArray qt_readlink(const char *path)
60{
61#ifndef PATH_MAX
62 // suitably large value that won't consume too much memory
63# define PATH_MAX 1024*1024
64#endif
65
66 QByteArray buf(256, Qt::Uninitialized);
67
68 ssize_t len = ::readlink(path: path, buf: buf.data(), len: buf.size());
69 while (len == buf.size()) {
70 // readlink(2) will fill our buffer and not necessarily terminate with NUL;
71 if (buf.size() >= PATH_MAX) {
72 errno = ENAMETOOLONG;
73 return QByteArray();
74 }
75
76 // double the size and try again
77 buf.resize(size: buf.size() * 2);
78 len = ::readlink(path: path, buf: buf.data(), len: buf.size());
79 }
80
81 if (len == -1)
82 return QByteArray();
83
84 buf.resize(size: len);
85 return buf;
86}
87
88#if defined(Q_PROCESSOR_X86_32) && defined(__GLIBC__)
89# if !__GLIBC_PREREQ(2, 22)
90// glibc prior to release 2.22 had a bug that suppresses the third argument to
91// open() / open64() / openat(), causing file creation with O_TMPFILE to have
92// the wrong permissions. So we bypass the glibc implementation and go straight
93// for the syscall. See
94// https://sourceware.org/git/?p=glibc.git;a=commit;h=65f6f938cd562a614a68e15d0581a34b177ec29d
95int qt_open64(const char *pathname, int flags, mode_t mode)
96{
97 return syscall(SYS_open, pathname, flags | O_LARGEFILE, mode);
98}
99# endif
100#endif
101
102#ifndef QT_BOOTSTRAPPED
103
104#if QT_CONFIG(poll_pollts)
105# define ppoll pollts
106#endif
107
108static inline bool time_update(struct timespec *tv, const struct timespec &start,
109 const struct timespec &timeout)
110{
111 // clock source is (hopefully) monotonic, so we can recalculate how much timeout is left;
112 // if it isn't monotonic, we'll simply hope that it hasn't jumped, because we have no alternative
113 struct timespec now = qt_gettime();
114 *tv = timeout + start - now;
115 return tv->tv_sec >= 0;
116}
117
118#if QT_CONFIG(poll_poll)
119static inline int timespecToMillisecs(const struct timespec *ts)
120{
121 return (ts == NULL) ? -1 :
122 (ts->tv_sec * 1000) + (ts->tv_nsec / 1000000);
123}
124#endif
125
126// defined in qpoll.cpp
127int qt_poll(struct pollfd *fds, nfds_t nfds, const struct timespec *timeout_ts);
128
129static inline int qt_ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *timeout_ts)
130{
131#if QT_CONFIG(poll_ppoll) || QT_CONFIG(poll_pollts)
132 return ::ppoll(fds: fds, nfds: nfds, timeout: timeout_ts, ss: nullptr);
133#elif QT_CONFIG(poll_poll)
134 return ::poll(fds, nfds, timespecToMillisecs(timeout_ts));
135#elif QT_CONFIG(poll_select)
136 return qt_poll(fds, nfds, timeout_ts);
137#else
138 // configure.json reports an error when everything is not available
139#endif
140}
141
142
143/*!
144 \internal
145
146 Behaves as close to POSIX poll(2) as practical but may be implemented
147 using select(2) where necessary. In that case, returns -1 and sets errno
148 to EINVAL if passed any descriptor greater than or equal to FD_SETSIZE.
149*/
150int qt_safe_poll(struct pollfd *fds, nfds_t nfds, const struct timespec *timeout_ts)
151{
152 if (!timeout_ts) {
153 // no timeout -> block forever
154 int ret;
155 EINTR_LOOP(ret, qt_ppoll(fds, nfds, nullptr));
156 return ret;
157 }
158
159 timespec start = qt_gettime();
160 timespec timeout = *timeout_ts;
161
162 // loop and recalculate the timeout as needed
163 forever {
164 const int ret = qt_ppoll(fds, nfds, timeout_ts: &timeout);
165 if (ret != -1 || errno != EINTR)
166 return ret;
167
168 // recalculate the timeout
169 if (!time_update(tv: &timeout, start, timeout: *timeout_ts)) {
170 // timeout during update
171 // or clock reset, fake timeout error
172 return 0;
173 }
174 }
175}
176
177#endif // QT_BOOTSTRAPPED
178
179QT_END_NAMESPACE
180

source code of qtbase/src/corelib/kernel/qcore_unix.cpp