Adding upstream version 9.1.upstream/9.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 412 insertions, 0 deletions

diff --git a/lib/utimecmp.c b/lib/utimecmp.c
new file mode 100644
index 0000000..3c00128
--- /dev/null
+++ b/lib/utimecmp.c
@@ -0,0 +1,412 @@
+/* utimecmp.c -- compare file timestamps
+
+   Copyright (C) 2004-2007, 2009-2022 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert.  */
+
+#include <config.h>
+
+#include "utimecmp.h"
+
+#include <fcntl.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "dirname.h"
+#include "hash.h"
+#include "intprops.h"
+#include "stat-time.h"
+#include "verify.h"
+
+#ifndef MAX
+# define MAX(a, b) ((a) > (b) ? (a) : (b))
+#endif
+
+#define BILLION (1000 * 1000 * 1000)
+
+/* Best possible resolution that utimens can set and stat can return,
+   due to system-call limitations.  It must be a power of 10 that is
+   no greater than 1 billion.  */
+#if HAVE_UTIMENSAT
+enum { SYSCALL_RESOLUTION = 1 };
+#elif defined _WIN32 && ! defined __CYGWIN__
+/* On native Windows, file times have 100 ns resolution. See
+   <https://docs.microsoft.com/en-us/windows/desktop/api/minwinbase/ns-minwinbase-filetime>  */
+enum { SYSCALL_RESOLUTION = 100 };
+#elif ((HAVE_FUTIMESAT || HAVE_WORKING_UTIMES)                  \
+       && (defined HAVE_STRUCT_STAT_ST_ATIM_TV_NSEC             \
+           || defined HAVE_STRUCT_STAT_ST_ATIMESPEC_TV_NSEC     \
+           || defined HAVE_STRUCT_STAT_ST_ATIMENSEC             \
+           || defined HAVE_STRUCT_STAT_ST_ATIM_ST__TIM_TV_NSEC  \
+           || defined HAVE_STRUCT_STAT_ST_SPARE1))
+enum { SYSCALL_RESOLUTION = 1000 };
+#else
+enum { SYSCALL_RESOLUTION = BILLION };
+#endif
+
+/* Describe a file system and its timestamp resolution in nanoseconds.  */
+struct fs_res
+{
+  /* Device number of file system.  */
+  dev_t dev;
+
+  /* An upper bound on the timestamp resolution of this file system,
+     ignoring any resolution that cannot be set via utimens.  It is
+     represented by an integer count of nanoseconds.  It must be
+     either 2 billion, or a power of 10 that is no greater than a
+     billion and is no less than SYSCALL_RESOLUTION.  */
+  int resolution;
+
+  /* True if RESOLUTION is known to be exact, and is not merely an
+     upper bound on the true resolution.  */
+  bool exact;
+};
+
+/* Hash some device info.  */
+static size_t
+dev_info_hash (void const *x, size_t table_size)
+{
+  struct fs_res const *p = x;
+
+  /* Beware signed arithmetic gotchas.  */
+  if (TYPE_SIGNED (dev_t) && SIZE_MAX < MAX (INT_MAX, TYPE_MAXIMUM (dev_t)))
+    {
+      uintmax_t dev = p->dev;
+      return dev % table_size;
+    }
+
+  return p->dev % table_size;
+}
+
+/* Compare two dev_info structs.  */
+static bool
+dev_info_compare (void const *x, void const *y)
+{
+  struct fs_res const *a = x;
+  struct fs_res const *b = y;
+  return a->dev == b->dev;
+}
+
+/* Return -1, 0, 1 based on whether the destination file (relative
+   to openat-like directory file descriptor DFD with name
+   DST_NAME and status DST_STAT) is older than SRC_STAT, the same age
+   as SRC_STAT, or newer than SRC_STAT, respectively.
+
+   DST_NAME may be NULL if OPTIONS is 0.
+
+   If OPTIONS & UTIMECMP_TRUNCATE_SOURCE, do the comparison after SRC is
+   converted to the destination's timestamp resolution as filtered through
+   utimens.  In this case, return -2 if the exact answer cannot be
+   determined; this can happen only if the timestamps are very close and
+   there is some trouble accessing the file system (e.g., the user does not
+   have permission to futz with the destination's timestamps).  */
+
+int
+utimecmp (char const *dst_name,
+          struct stat const *dst_stat,
+          struct stat const *src_stat,
+          int options)
+{
+  return utimecmpat (AT_FDCWD, dst_name, dst_stat, src_stat, options);
+}
+
+int
+utimecmpat (int dfd, char const *dst_name,
+            struct stat const *dst_stat,
+            struct stat const *src_stat,
+            int options)
+{
+  /* Things to watch out for:
+
+     The code uses a static hash table internally and is not safe in the
+     presence of signals, multiple threads, etc.  However, memory pressure
+     that prevents use of the hash table is not fatal - we just fall back
+     to redoing the computations on every call in that case.
+
+     int and long int might be 32 bits.  Many of the calculations store
+     numbers up to 2 billion, and multiply by 10; they have to avoid
+     multiplying 2 billion by 10, as this exceeds 32-bit capabilities.
+
+     time_t might be unsigned.  */
+
+  verify (TYPE_IS_INTEGER (time_t));
+
+  /* Destination and source timestamps.  */
+  time_t dst_s = dst_stat->st_mtime;
+  time_t src_s = src_stat->st_mtime;
+  int dst_ns = get_stat_mtime_ns (dst_stat);
+  int src_ns = get_stat_mtime_ns (src_stat);
+
+  if (options & UTIMECMP_TRUNCATE_SOURCE)
+    {
+#if defined _AIX
+      /* On AIX 7.2, on a jfs2 file system, the times may differ by up to
+         0.01 seconds in either direction.  But it does not seem to come
+         from clock ticks of 0.01 seconds each.  */
+      long long difference =
+        ((long long) dst_s - (long long) src_s) * BILLION
+        + ((long long) dst_ns - (long long) src_ns);
+      if (difference < 10000000 && difference > -10000000)
+        return 0;
+#endif
+
+      /* Look up the timestamp resolution for the destination device.  */
+
+      /* Hash table for caching information learned about devices.  */
+      static Hash_table *ht;
+
+      /* Information about the destination file system.  */
+      static struct fs_res *new_dst_res;
+      struct fs_res *dst_res = NULL;
+      struct fs_res tmp_dst_res;
+
+      /* timestamp resolution in nanoseconds.  */
+      int res;
+
+      /* Quick exit, if possible.  Since the worst resolution is 2
+         seconds, anything that differs by more than that does not
+         needs source truncation.  */
+      if (dst_s == src_s && dst_ns == src_ns)
+        return 0;
+      if (dst_s <= src_s - 2)
+        return -1;
+      if (src_s <= dst_s - 2)
+        return 1;
+
+      /* Try to do a hash lookup, but fall back to stack variables and
+         recomputation on low memory situations.  */
+      if (! ht)
+        ht = hash_initialize (16, NULL, dev_info_hash, dev_info_compare, free);
+      if (ht)
+        {
+          if (! new_dst_res)
+            {
+              new_dst_res = malloc (sizeof *new_dst_res);
+              if (!new_dst_res)
+                goto low_memory;
+              new_dst_res->resolution = 2 * BILLION;
+              new_dst_res->exact = false;
+            }
+          new_dst_res->dev = dst_stat->st_dev;
+          dst_res = hash_insert (ht, new_dst_res);
+          if (! dst_res)
+            goto low_memory;
+
+          if (dst_res == new_dst_res)
+            {
+              /* NEW_DST_RES is now in use in the hash table, so allocate a
+                 new entry next time.  */
+              new_dst_res = NULL;
+            }
+        }
+      else
+        {
+        low_memory:
+          if (ht)
+            {
+              tmp_dst_res.dev = dst_stat->st_dev;
+              dst_res = hash_lookup (ht, &tmp_dst_res);
+            }
+          if (!dst_res)
+            {
+              dst_res = &tmp_dst_res;
+              dst_res->resolution = 2 * BILLION;
+              dst_res->exact = false;
+            }
+        }
+
+      res = dst_res->resolution;
+
+#ifdef _PC_TIMESTAMP_RESOLUTION
+      /* If the system will tell us the resolution, we're set!  */
+      if (! dst_res->exact)
+        {
+          res = -1;
+          if (dfd == AT_FDCWD)
+            res = pathconf (dst_name, _PC_TIMESTAMP_RESOLUTION);
+          else
+            {
+              char *dstdir = mdir_name (dst_name);
+              if (dstdir)
+                {
+                  int destdirfd = openat (dfd, dstdir,
+                                          O_SEARCH | O_CLOEXEC | O_DIRECTORY);
+                  if (0 <= destdirfd)
+                    {
+                      res = fpathconf (destdirfd, _PC_TIMESTAMP_RESOLUTION);
+                      close (destdirfd);
+                    }
+                  free (dstdir);
+                }
+            }
+          if (0 < res)
+            {
+              dst_res->resolution = res;
+              dst_res->exact = true;
+            }
+        }
+#endif
+
+      if (! dst_res->exact)
+        {
+          /* This file system's resolution is not known exactly.
+             Deduce it, and store the result in the hash table.  */
+
+          time_t dst_a_s = dst_stat->st_atime;
+          time_t dst_c_s = dst_stat->st_ctime;
+          time_t dst_m_s = dst_s;
+          int dst_a_ns = get_stat_atime_ns (dst_stat);
+          int dst_c_ns = get_stat_ctime_ns (dst_stat);
+          int dst_m_ns = dst_ns;
+
+          /* Set RES to an upper bound on the file system resolution
+             (after truncation due to SYSCALL_RESOLUTION) by inspecting
+             the atime, ctime and mtime of the existing destination.
+             We don't know of any file system that stores atime or
+             ctime with a higher precision than mtime, so it's valid to
+             look at them too.  */
+          {
+            bool odd_second = (dst_a_s | dst_c_s | dst_m_s) & 1;
+
+            if (SYSCALL_RESOLUTION == BILLION)
+              {
+                if (odd_second | dst_a_ns | dst_c_ns | dst_m_ns)
+                  res = BILLION;
+              }
+            else
+              {
+                int a = dst_a_ns;
+                int c = dst_c_ns;
+                int m = dst_m_ns;
+
+                /* Write it this way to avoid mistaken GCC warning
+                   about integer overflow in constant expression.  */
+                int SR10 = SYSCALL_RESOLUTION;  SR10 *= 10;
+
+                if ((a % SR10 | c % SR10 | m % SR10) != 0)
+                  res = SYSCALL_RESOLUTION;
+                else
+                  for (res = SR10, a /= SR10, c /= SR10, m /= SR10;
+                       (res < dst_res->resolution
+                        && (a % 10 | c % 10 | m % 10) == 0);
+                       res *= 10, a /= 10, c /= 10, m /= 10)
+                    if (res == BILLION)
+                      {
+                        if (! odd_second)
+                          res *= 2;
+                        break;
+                      }
+              }
+
+            dst_res->resolution = res;
+          }
+
+          if (SYSCALL_RESOLUTION < res)
+            {
+              struct timespec timespec[2];
+              struct stat dst_status;
+
+              /* Ignore source timestamp information that must necessarily
+                 be lost when filtered through utimens.  */
+              src_ns -= src_ns % SYSCALL_RESOLUTION;
+
+              /* If the timestamps disagree widely enough, there's no need
+                 to interrogate the file system to deduce the exact
+                 timestamp resolution; return the answer directly.  */
+              {
+                time_t s = src_s & ~ (res == 2 * BILLION ? 1 : 0);
+                if (src_s < dst_s || (src_s == dst_s && src_ns <= dst_ns))
+                  return 1;
+                if (dst_s < s
+                    || (dst_s == s && dst_ns < src_ns - src_ns % res))
+                  return -1;
+              }
+
+              /* Determine the actual timestamp resolution for the
+                 destination file system (after truncation due to
+                 SYSCALL_RESOLUTION) by setting the access timestamp of the
+                 destination to the existing access time, except with
+                 trailing nonzero digits.  */
+
+              timespec[0].tv_sec = dst_a_s;
+              timespec[0].tv_nsec = dst_a_ns;
+              timespec[1].tv_sec = dst_m_s | (res == 2 * BILLION);
+              timespec[1].tv_nsec = dst_m_ns + res / 9;
+
+              if (utimensat (dfd, dst_name, timespec, AT_SYMLINK_NOFOLLOW))
+                return -2;
+
+              /* Read the modification time that was set.  */
+              {
+                int stat_result
+                  = fstatat (dfd, dst_name, &dst_status, AT_SYMLINK_NOFOLLOW);
+
+                if (stat_result
+                    | (dst_status.st_mtime ^ dst_m_s)
+                    | (get_stat_mtime_ns (&dst_status) ^ dst_m_ns))
+                  {
+                    /* The modification time changed, or we can't tell whether
+                       it changed.  Change it back as best we can.  */
+                    timespec[1].tv_sec = dst_m_s;
+                    timespec[1].tv_nsec = dst_m_ns;
+                    utimensat (dfd, dst_name, timespec, AT_SYMLINK_NOFOLLOW);
+                  }
+
+                if (stat_result != 0)
+                  return -2;
+              }
+
+              /* Determine the exact resolution from the modification time
+                 that was read back.  */
+              {
+                int old_res = res;
+                int a = (BILLION * (dst_status.st_mtime & 1)
+                         + get_stat_mtime_ns (&dst_status));
+
+                res = SYSCALL_RESOLUTION;
+
+                for (a /= res; a % 10 == 0; a /= 10)
+                  {
+                    if (res == BILLION)
+                      {
+                        res *= 2;
+                        break;
+                      }
+                    res *= 10;
+                    if (res == old_res)
+                      break;
+                  }
+              }
+            }
+
+          dst_res->resolution = res;
+          dst_res->exact = true;
+        }
+
+      /* Truncate the source's timestamp according to the resolution.  */
+      src_s &= ~ (res == 2 * BILLION ? 1 : 0);
+      src_ns -= src_ns % res;
+    }
+
+  /* Compare the timestamps and return -1, 0, 1 accordingly.  */
+  return (_GL_CMP (dst_s, src_s)
+          + ((dst_s == src_s ? ~0 : 0) & _GL_CMP (dst_ns, src_ns)));
+}