1 //===----------------------------------------------------------------------===////
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===////
8 
9 #ifndef FILESYSTEM_TIME_UTILS_H
10 #define FILESYSTEM_TIME_UTILS_H
11 
12 #include <__config>
13 #include <array>
14 #include <chrono>
15 #include <filesystem>
16 #include <limits>
17 #include <ratio>
18 #include <system_error>
19 #include <type_traits>
20 #include <utility>
21 
22 #include "error.h"
23 #include "format_string.h"
24 
25 #if defined(_LIBCPP_WIN32API)
26 # define WIN32_LEAN_AND_MEAN
27 # define NOMINMAX
28 # include <windows.h>
29 #else
30 # include <fcntl.h>
31 # include <sys/stat.h>
32 # include <sys/time.h> // for ::utimes as used in __last_write_time
33 #endif
34 
35 // We can use the presence of UTIME_OMIT to detect platforms that provide utimensat.
36 #if defined(UTIME_OMIT)
37 # define _LIBCPP_USE_UTIMENSAT
38 #endif
39 
40 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
41 
42 namespace detail {
43 
44 #if defined(_LIBCPP_WIN32API)
45 // Various C runtime versions (UCRT, or the legacy msvcrt.dll used by
46 // some mingw toolchains) provide different stat function implementations,
47 // with a number of limitations with respect to what we want from the
48 // stat function. Instead provide our own which does exactly what we want,
49 // along with our own stat structure and flag macros.
50 
51 struct TimeSpec {
52   int64_t tv_sec;
53   int64_t tv_nsec;
54 };
55 struct StatT {
56   unsigned st_mode;
57   TimeSpec st_atim;
58   TimeSpec st_mtim;
59   uint64_t st_dev; // FILE_ID_INFO::VolumeSerialNumber
60   struct FileIdStruct {
61     unsigned char id[16]; // FILE_ID_INFO::FileId
62     bool operator==(const FileIdStruct &other) const {
63       for (int i = 0; i < 16; i++)
64         if (id[i] != other.id[i])
65           return false;
66       return true;
67     }
68   } st_ino;
69   uint32_t st_nlink;
70   uintmax_t st_size;
71 };
72 
73 // There were 369 years and 89 leap days from the Windows epoch
74 // (1601) to the Unix epoch (1970).
75 #define FILE_TIME_OFFSET_SECS (uint64_t(369 * 365 + 89) * (24 * 60 * 60))
76 
77 inline TimeSpec filetime_to_timespec(LARGE_INTEGER li) {
78   TimeSpec ret;
79   ret.tv_sec = li.QuadPart / 10000000 - FILE_TIME_OFFSET_SECS;
80   ret.tv_nsec = (li.QuadPart % 10000000) * 100;
81   return ret;
82 }
83 
84 inline TimeSpec filetime_to_timespec(FILETIME ft) {
85   LARGE_INTEGER li;
86   li.LowPart = ft.dwLowDateTime;
87   li.HighPart = ft.dwHighDateTime;
88   return filetime_to_timespec(li);
89 }
90 
91 inline FILETIME timespec_to_filetime(TimeSpec ts) {
92   LARGE_INTEGER li;
93   li.QuadPart =
94       ts.tv_nsec / 100 + (ts.tv_sec + FILE_TIME_OFFSET_SECS) * 10000000;
95   FILETIME ft;
96   ft.dwLowDateTime = li.LowPart;
97   ft.dwHighDateTime = li.HighPart;
98   return ft;
99 }
100 
101 #else
102 using TimeSpec = struct timespec;
103 using TimeVal = struct timeval;
104 using StatT = struct stat;
105 
106 inline TimeVal make_timeval(TimeSpec const& ts) {
107   using namespace chrono;
108   auto Convert = [](long nsec) {
109     using int_type = decltype(std::declval<TimeVal>().tv_usec);
110     auto dur = duration_cast<microseconds>(nanoseconds(nsec)).count();
111     return static_cast<int_type>(dur);
112   };
113   TimeVal TV = {};
114   TV.tv_sec = ts.tv_sec;
115   TV.tv_usec = Convert(ts.tv_nsec);
116   return TV;
117 }
118 #endif
119 
120 using chrono::duration;
121 using chrono::duration_cast;
122 
123 template <class FileTimeT, class TimeT,
124           bool IsFloat = is_floating_point<typename FileTimeT::rep>::value>
125 struct time_util_base {
126   using rep = typename FileTimeT::rep;
127   using fs_duration = typename FileTimeT::duration;
128   using fs_seconds = duration<rep>;
129   using fs_nanoseconds = duration<rep, nano>;
130   using fs_microseconds = duration<rep, micro>;
131 
132   static constexpr rep max_seconds =
133       duration_cast<fs_seconds>(FileTimeT::duration::max()).count();
134 
135   static constexpr rep max_nsec =
136       duration_cast<fs_nanoseconds>(FileTimeT::duration::max() -
137                                     fs_seconds(max_seconds))
138           .count();
139 
140   static constexpr rep min_seconds =
141       duration_cast<fs_seconds>(FileTimeT::duration::min()).count();
142 
143   static constexpr rep min_nsec_timespec =
144       duration_cast<fs_nanoseconds>(
145           (FileTimeT::duration::min() - fs_seconds(min_seconds)) +
146           fs_seconds(1))
147           .count();
148 
149 private:
150   static _LIBCPP_CONSTEXPR fs_duration get_min_nsecs() {
151     return duration_cast<fs_duration>(
152         fs_nanoseconds(min_nsec_timespec) -
153         duration_cast<fs_nanoseconds>(fs_seconds(1)));
154   }
155   // Static assert that these values properly round trip.
156   static_assert(fs_seconds(min_seconds) + get_min_nsecs() ==
157                     FileTimeT::duration::min(),
158                 "value doesn't roundtrip");
159 
160   static _LIBCPP_CONSTEXPR_SINCE_CXX14 bool check_range() {
161     // This kinda sucks, but it's what happens when we don't have __int128_t.
162     if (sizeof(TimeT) == sizeof(rep)) {
163       typedef duration<long long, ratio<3600 * 24 * 365> > Years;
164       return duration_cast<Years>(fs_seconds(max_seconds)) > Years(250) &&
165              duration_cast<Years>(fs_seconds(min_seconds)) < Years(-250);
166     }
167     return max_seconds >= numeric_limits<TimeT>::max() &&
168            min_seconds <= numeric_limits<TimeT>::min();
169   }
170 #if _LIBCPP_STD_VER >= 14
171   static_assert(check_range(), "the representable range is unacceptable small");
172 #endif
173 };
174 
175 template <class FileTimeT, class TimeT>
176 struct time_util_base<FileTimeT, TimeT, true> {
177   using rep = typename FileTimeT::rep;
178   using fs_duration = typename FileTimeT::duration;
179   using fs_seconds = duration<rep>;
180   using fs_nanoseconds = duration<rep, nano>;
181   using fs_microseconds = duration<rep, micro>;
182 
183   static const rep max_seconds;
184   static const rep max_nsec;
185   static const rep min_seconds;
186   static const rep min_nsec_timespec;
187 };
188 
189 template <class FileTimeT, class TimeT>
190 const typename FileTimeT::rep
191     time_util_base<FileTimeT, TimeT, true>::max_seconds =
192         duration_cast<fs_seconds>(FileTimeT::duration::max()).count();
193 
194 template <class FileTimeT, class TimeT>
195 const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::max_nsec =
196     duration_cast<fs_nanoseconds>(FileTimeT::duration::max() -
197                                   fs_seconds(max_seconds))
198         .count();
199 
200 template <class FileTimeT, class TimeT>
201 const typename FileTimeT::rep
202     time_util_base<FileTimeT, TimeT, true>::min_seconds =
203         duration_cast<fs_seconds>(FileTimeT::duration::min()).count();
204 
205 template <class FileTimeT, class TimeT>
206 const typename FileTimeT::rep
207     time_util_base<FileTimeT, TimeT, true>::min_nsec_timespec =
208         duration_cast<fs_nanoseconds>((FileTimeT::duration::min() -
209                                        fs_seconds(min_seconds)) +
210                                       fs_seconds(1))
211             .count();
212 
213 template <class FileTimeT, class TimeT, class TimeSpecT>
214 struct time_util : time_util_base<FileTimeT, TimeT> {
215   using Base = time_util_base<FileTimeT, TimeT>;
216   using Base::max_nsec;
217   using Base::max_seconds;
218   using Base::min_nsec_timespec;
219   using Base::min_seconds;
220 
221   using typename Base::fs_duration;
222   using typename Base::fs_microseconds;
223   using typename Base::fs_nanoseconds;
224   using typename Base::fs_seconds;
225 
226 public:
227   template <class CType, class ChronoType>
228   static _LIBCPP_CONSTEXPR_SINCE_CXX14 bool checked_set(CType* out,
229                                                         ChronoType time) {
230     using Lim = numeric_limits<CType>;
231     if (time > Lim::max() || time < Lim::min())
232       return false;
233     *out = static_cast<CType>(time);
234     return true;
235   }
236 
237   static _LIBCPP_CONSTEXPR_SINCE_CXX14 bool is_representable(TimeSpecT tm) {
238     if (tm.tv_sec >= 0) {
239       return tm.tv_sec < max_seconds ||
240              (tm.tv_sec == max_seconds && tm.tv_nsec <= max_nsec);
241     } else if (tm.tv_sec == (min_seconds - 1)) {
242       return tm.tv_nsec >= min_nsec_timespec;
243     } else {
244       return tm.tv_sec >= min_seconds;
245     }
246   }
247 
248   static _LIBCPP_CONSTEXPR_SINCE_CXX14 bool is_representable(FileTimeT tm) {
249     auto secs = duration_cast<fs_seconds>(tm.time_since_epoch());
250     auto nsecs = duration_cast<fs_nanoseconds>(tm.time_since_epoch() - secs);
251     if (nsecs.count() < 0) {
252       secs = secs + fs_seconds(1);
253       nsecs = nsecs + fs_seconds(1);
254     }
255     using TLim = numeric_limits<TimeT>;
256     if (secs.count() >= 0)
257       return secs.count() <= TLim::max();
258     return secs.count() >= TLim::min();
259   }
260 
261   static _LIBCPP_CONSTEXPR_SINCE_CXX14 FileTimeT
262   convert_from_timespec(TimeSpecT tm) {
263     if (tm.tv_sec >= 0 || tm.tv_nsec == 0) {
264       return FileTimeT(fs_seconds(tm.tv_sec) +
265                        duration_cast<fs_duration>(fs_nanoseconds(tm.tv_nsec)));
266     } else { // tm.tv_sec < 0
267       auto adj_subsec = duration_cast<fs_duration>(fs_seconds(1) -
268                                                    fs_nanoseconds(tm.tv_nsec));
269       auto Dur = fs_seconds(tm.tv_sec + 1) - adj_subsec;
270       return FileTimeT(Dur);
271     }
272   }
273 
274   template <class SubSecT>
275   static _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
276   set_times_checked(TimeT* sec_out, SubSecT* subsec_out, FileTimeT tp) {
277     auto dur = tp.time_since_epoch();
278     auto sec_dur = duration_cast<fs_seconds>(dur);
279     auto subsec_dur = duration_cast<fs_nanoseconds>(dur - sec_dur);
280     // The tv_nsec and tv_usec fields must not be negative so adjust accordingly
281     if (subsec_dur.count() < 0) {
282       if (sec_dur.count() > min_seconds) {
283         sec_dur = sec_dur - fs_seconds(1);
284         subsec_dur = subsec_dur + fs_seconds(1);
285       } else {
286         subsec_dur = fs_nanoseconds::zero();
287       }
288     }
289     return checked_set(sec_out, sec_dur.count()) &&
290            checked_set(subsec_out, subsec_dur.count());
291   }
292   static _LIBCPP_CONSTEXPR_SINCE_CXX14 bool convert_to_timespec(TimeSpecT& dest,
293                                                                 FileTimeT tp) {
294     if (!is_representable(tp))
295       return false;
296     return set_times_checked(&dest.tv_sec, &dest.tv_nsec, tp);
297   }
298 };
299 
300 #if defined(_LIBCPP_WIN32API)
301 using fs_time = time_util<file_time_type, int64_t, TimeSpec>;
302 #else
303 using fs_time = time_util<file_time_type, time_t, TimeSpec>;
304 #endif
305 
306 #if defined(__APPLE__)
307 inline TimeSpec extract_mtime(StatT const& st) { return st.st_mtimespec; }
308 inline TimeSpec extract_atime(StatT const& st) { return st.st_atimespec; }
309 #elif defined(__MVS__)
310 inline TimeSpec extract_mtime(StatT const& st) {
311   TimeSpec TS = {st.st_mtime, 0};
312   return TS;
313 }
314 inline TimeSpec extract_atime(StatT const& st) {
315   TimeSpec TS = {st.st_atime, 0};
316   return TS;
317 }
318 #elif defined(_AIX)
319 inline TimeSpec extract_mtime(StatT const& st) {
320   TimeSpec TS = {st.st_mtime, st.st_mtime_n};
321   return TS;
322 }
323 inline TimeSpec extract_atime(StatT const& st) {
324   TimeSpec TS = {st.st_atime, st.st_atime_n};
325   return TS;
326 }
327 #else
328 inline TimeSpec extract_mtime(StatT const& st) { return st.st_mtim; }
329 inline TimeSpec extract_atime(StatT const& st) { return st.st_atim; }
330 #endif
331 
332 #ifndef _LIBCPP_HAS_NO_FILESYSTEM
333 
334 #if !defined(_LIBCPP_WIN32API)
335 inline bool posix_utimes(const path& p, std::array<TimeSpec, 2> const& TS,
336                   error_code& ec) {
337   TimeVal ConvertedTS[2] = {make_timeval(TS[0]), make_timeval(TS[1])};
338   if (::utimes(p.c_str(), ConvertedTS) == -1) {
339     ec = capture_errno();
340     return true;
341   }
342   return false;
343 }
344 
345 #if defined(_LIBCPP_USE_UTIMENSAT)
346 inline bool posix_utimensat(const path& p, std::array<TimeSpec, 2> const& TS,
347                             error_code& ec) {
348   if (::utimensat(AT_FDCWD, p.c_str(), TS.data(), 0) == -1) {
349     ec = capture_errno();
350     return true;
351   }
352   return false;
353 }
354 #endif
355 
356 inline bool set_file_times(const path& p, std::array<TimeSpec, 2> const& TS,
357                            error_code& ec) {
358 #if !defined(_LIBCPP_USE_UTIMENSAT)
359   return posix_utimes(p, TS, ec);
360 #else
361   return posix_utimensat(p, TS, ec);
362 #endif
363 }
364 
365 #endif // !_LIBCPP_WIN32API
366 
367 inline file_time_type __extract_last_write_time(const path& p, const StatT& st,
368                                                 error_code* ec) {
369   using detail::fs_time;
370   ErrorHandler<file_time_type> err("last_write_time", ec, &p);
371 
372   auto ts = detail::extract_mtime(st);
373   if (!fs_time::is_representable(ts))
374     return err.report(errc::value_too_large);
375 
376   return fs_time::convert_from_timespec(ts);
377 }
378 
379 #endif // !_LIBCPP_HAS_NO_FILESYSTEM
380 
381 } // end namespace detail
382 
383 _LIBCPP_END_NAMESPACE_FILESYSTEM
384 
385 #endif // FILESYSTEM_TIME_UTILS_H
386