libcxx/src/filesystem/time_utils.h

   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 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 constexpr 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 constexpr 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 constexpr 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 constexpr 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 constexpr 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 constexpr 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 constexpr 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