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 = ts.tv_nsec / 100 + (ts.tv_sec + FILE_TIME_OFFSET_SECS) * 10000000;
  94   FILETIME ft;
  95   ft.dwLowDateTime  = li.LowPart;
  96   ft.dwHighDateTime = li.HighPart;
  97   return ft;
  98 }
  99
 100 #else
 101 using TimeSpec = struct timespec;
 102 using TimeVal  = struct timeval;
 103 using StatT    = struct stat;
 104
 105 inline TimeVal make_timeval(TimeSpec const& ts) {
 106   using namespace chrono;
 107   auto Convert = [](long nsec) {
 108     using int_type = decltype(std::declval<TimeVal>().tv_usec);
 109     auto dur       = duration_cast<microseconds>(nanoseconds(nsec)).count();
 110     return static_cast<int_type>(dur);
 111   };
 112   TimeVal TV = {};
 113   TV.tv_sec  = ts.tv_sec;
 114   TV.tv_usec = Convert(ts.tv_nsec);
 115   return TV;
 116 }
 117 #endif
 118
 119 using chrono::duration;
 120 using chrono::duration_cast;
 121
 122 template <class FileTimeT, class TimeT, bool IsFloat = is_floating_point<typename FileTimeT::rep>::value>
 123 struct time_util_base {
 124   using rep             = typename FileTimeT::rep;
 125   using fs_duration     = typename FileTimeT::duration;
 126   using fs_seconds      = duration<rep>;
 127   using fs_nanoseconds  = duration<rep, nano>;
 128   using fs_microseconds = duration<rep, micro>;
 129
 130   static constexpr rep max_seconds = duration_cast<fs_seconds>(FileTimeT::duration::max()).count();
 131
 132   static constexpr rep max_nsec =
 133       duration_cast<fs_nanoseconds>(FileTimeT::duration::max() - fs_seconds(max_seconds)).count();
 134
 135   static constexpr rep min_seconds = duration_cast<fs_seconds>(FileTimeT::duration::min()).count();
 136
 137   static constexpr rep min_nsec_timespec =
 138       duration_cast<fs_nanoseconds>((FileTimeT::duration::min() - fs_seconds(min_seconds)) + fs_seconds(1)).count();
 139
 140 private:
 141   static constexpr fs_duration get_min_nsecs() {
 142     return duration_cast<fs_duration>(fs_nanoseconds(min_nsec_timespec) - duration_cast<fs_nanoseconds>(fs_seconds(1)));
 143   }
 144   // Static assert that these values properly round trip.
 145   static_assert(fs_seconds(min_seconds) + get_min_nsecs() == FileTimeT::duration::min(), "value doesn't roundtrip");
 146
 147   static constexpr bool check_range() {
 148     // This kinda sucks, but it's what happens when we don't have __int128_t.
 149     if (sizeof(TimeT) == sizeof(rep)) {
 150       typedef duration<long long, ratio<3600 * 24 * 365> > Years;
 151       return duration_cast<Years>(fs_seconds(max_seconds)) > Years(250) &&
 152              duration_cast<Years>(fs_seconds(min_seconds)) < Years(-250);
 153     }
 154     return max_seconds >= numeric_limits<TimeT>::max() && min_seconds <= numeric_limits<TimeT>::min();
 155   }
 156 #if _LIBCPP_STD_VER >= 14
 157   static_assert(check_range(), "the representable range is unacceptable small");
 158 #endif
 159 };
 160
 161 template <class FileTimeT, class TimeT>
 162 struct time_util_base<FileTimeT, TimeT, true> {
 163   using rep             = typename FileTimeT::rep;
 164   using fs_duration     = typename FileTimeT::duration;
 165   using fs_seconds      = duration<rep>;
 166   using fs_nanoseconds  = duration<rep, nano>;
 167   using fs_microseconds = duration<rep, micro>;
 168
 169   static const rep max_seconds;
 170   static const rep max_nsec;
 171   static const rep min_seconds;
 172   static const rep min_nsec_timespec;
 173 };
 174
 175 template <class FileTimeT, class TimeT>
 176 const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::max_seconds =
 177     duration_cast<fs_seconds>(FileTimeT::duration::max()).count();
 178
 179 template <class FileTimeT, class TimeT>
 180 const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::max_nsec =
 181     duration_cast<fs_nanoseconds>(FileTimeT::duration::max() - fs_seconds(max_seconds)).count();
 182
 183 template <class FileTimeT, class TimeT>
 184 const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::min_seconds =
 185     duration_cast<fs_seconds>(FileTimeT::duration::min()).count();
 186
 187 template <class FileTimeT, class TimeT>
 188 const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::min_nsec_timespec =
 189     duration_cast<fs_nanoseconds>((FileTimeT::duration::min() - fs_seconds(min_seconds)) + fs_seconds(1)).count();
 190
 191 template <class FileTimeT, class TimeT, class TimeSpecT>
 192 struct time_util : time_util_base<FileTimeT, TimeT> {
 193   using Base = time_util_base<FileTimeT, TimeT>;
 194   using Base::max_nsec;
 195   using Base::max_seconds;
 196   using Base::min_nsec_timespec;
 197   using Base::min_seconds;
 198
 199   using typename Base::fs_duration;
 200   using typename Base::fs_microseconds;
 201   using typename Base::fs_nanoseconds;
 202   using typename Base::fs_seconds;
 203
 204 public:
 205   template <class CType, class ChronoType>
 206   static constexpr bool checked_set(CType* out, ChronoType time) {
 207     using Lim = numeric_limits<CType>;
 208     if (time > Lim::max() || time < Lim::min())
 209       return false;
 210     *out = static_cast<CType>(time);
 211     return true;
 212   }
 213
 214   static constexpr bool is_representable(TimeSpecT tm) {
 215     if (tm.tv_sec >= 0) {
 216       return tm.tv_sec < max_seconds || (tm.tv_sec == max_seconds && tm.tv_nsec <= max_nsec);
 217     } else if (tm.tv_sec == (min_seconds - 1)) {
 218       return tm.tv_nsec >= min_nsec_timespec;
 219     } else {
 220       return tm.tv_sec >= min_seconds;
 221     }
 222   }
 223
 224   static constexpr bool is_representable(FileTimeT tm) {
 225     auto secs  = duration_cast<fs_seconds>(tm.time_since_epoch());
 226     auto nsecs = duration_cast<fs_nanoseconds>(tm.time_since_epoch() - secs);
 227     if (nsecs.count() < 0) {
 228       secs  = secs + fs_seconds(1);
 229       nsecs = nsecs + fs_seconds(1);
 230     }
 231     using TLim = numeric_limits<TimeT>;
 232     if (secs.count() >= 0)
 233       return secs.count() <= TLim::max();
 234     return secs.count() >= TLim::min();
 235   }
 236
 237   static constexpr FileTimeT convert_from_timespec(TimeSpecT tm) {
 238     if (tm.tv_sec >= 0 || tm.tv_nsec == 0) {
 239       return FileTimeT(fs_seconds(tm.tv_sec) + duration_cast<fs_duration>(fs_nanoseconds(tm.tv_nsec)));
 240     } else { // tm.tv_sec < 0
 241       auto adj_subsec = duration_cast<fs_duration>(fs_seconds(1) - fs_nanoseconds(tm.tv_nsec));
 242       auto Dur        = fs_seconds(tm.tv_sec + 1) - adj_subsec;
 243       return FileTimeT(Dur);
 244     }
 245   }
 246
 247   template <class SubSecT>
 248   static constexpr bool set_times_checked(TimeT* sec_out, SubSecT* subsec_out, FileTimeT tp) {
 249     auto dur        = tp.time_since_epoch();
 250     auto sec_dur    = duration_cast<fs_seconds>(dur);
 251     auto subsec_dur = duration_cast<fs_nanoseconds>(dur - sec_dur);
 252     // The tv_nsec and tv_usec fields must not be negative so adjust accordingly
 253     if (subsec_dur.count() < 0) {
 254       if (sec_dur.count() > min_seconds) {
 255         sec_dur    = sec_dur - fs_seconds(1);
 256         subsec_dur = subsec_dur + fs_seconds(1);
 257       } else {
 258         subsec_dur = fs_nanoseconds::zero();
 259       }
 260     }
 261     return checked_set(sec_out, sec_dur.count()) && checked_set(subsec_out, subsec_dur.count());
 262   }
 263   static constexpr bool convert_to_timespec(TimeSpecT& dest, FileTimeT tp) {
 264     if (!is_representable(tp))
 265       return false;
 266     return set_times_checked(&dest.tv_sec, &dest.tv_nsec, tp);
 267   }
 268 };
 269
 270 #if defined(_LIBCPP_WIN32API)
 271 using fs_time = time_util<file_time_type, int64_t, TimeSpec>;
 272 #else
 273 using fs_time = time_util<file_time_type, time_t, TimeSpec>;
 274 #endif
 275
 276 #if defined(__APPLE__)
 277 inline TimeSpec extract_mtime(StatT const& st) { return st.st_mtimespec; }
 278 inline TimeSpec extract_atime(StatT const& st) { return st.st_atimespec; }
 279 #elif defined(__MVS__)
 280 inline TimeSpec extract_mtime(StatT const& st) {
 281   TimeSpec TS = {st.st_mtime, 0};
 282   return TS;
 283 }
 284 inline TimeSpec extract_atime(StatT const& st) {
 285   TimeSpec TS = {st.st_atime, 0};
 286   return TS;
 287 }
 288 #elif defined(_AIX)
 289 inline TimeSpec extract_mtime(StatT const& st) {
 290   TimeSpec TS = {st.st_mtime, st.st_mtime_n};
 291   return TS;
 292 }
 293 inline TimeSpec extract_atime(StatT const& st) {
 294   TimeSpec TS = {st.st_atime, st.st_atime_n};
 295   return TS;
 296 }
 297 #else
 298 inline TimeSpec extract_mtime(StatT const& st) { return st.st_mtim; }
 299 inline TimeSpec extract_atime(StatT const& st) { return st.st_atim; }
 300 #endif
 301
 302 #ifndef _LIBCPP_HAS_NO_FILESYSTEM
 303
 304 #  if !defined(_LIBCPP_WIN32API)
 305 inline bool posix_utimes(const path& p, std::array<TimeSpec, 2> const& TS, error_code& ec) {
 306   TimeVal ConvertedTS[2] = {make_timeval(TS[0]), make_timeval(TS[1])};
 307   if (::utimes(p.c_str(), ConvertedTS) == -1) {
 308     ec = capture_errno();
 309     return true;
 310   }
 311   return false;
 312 }
 313
 314 #    if defined(_LIBCPP_USE_UTIMENSAT)
 315 inline bool posix_utimensat(const path& p, std::array<TimeSpec, 2> const& TS, error_code& ec) {
 316   if (::utimensat(AT_FDCWD, p.c_str(), TS.data(), 0) == -1) {
 317     ec = capture_errno();
 318     return true;
 319   }
 320   return false;
 321 }
 322 #    endif
 323
 324 inline bool set_file_times(const path& p, std::array<TimeSpec, 2> const& TS, error_code& ec) {
 325 #    if !defined(_LIBCPP_USE_UTIMENSAT)
 326   return posix_utimes(p, TS, ec);
 327 #    else
 328   return posix_utimensat(p, TS, ec);
 329 #    endif
 330 }
 331
 332 #  endif // !_LIBCPP_WIN32API
 333
 334 inline file_time_type __extract_last_write_time(const path& p, const StatT& st, error_code* ec) {
 335   using detail::fs_time;
 336   ErrorHandler<file_time_type> err("last_write_time", ec, &p);
 337
 338   auto ts = detail::extract_mtime(st);
 339   if (!fs_time::is_representable(ts))
 340     return err.report(errc::value_too_large);
 341
 342   return fs_time::convert_from_timespec(ts);
 343 }
 344
 345 #endif // !_LIBCPP_HAS_NO_FILESYSTEM
 346
 347 } // end namespace detail
 348
 349 _LIBCPP_END_NAMESPACE_FILESYSTEM
 350
 351 #endif // FILESYSTEM_TIME_UTILS_H