X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=tests%2Fnap.h;h=229e4d3f8d4165cc1b828e691755642be754b905;hb=4e1dc0e3d73be7c53e10b8541a0313df3d1ae35b;hp=6dfb0a077bcca786ca6a5d1aa599dab9903bf2fb;hpb=1602f0afed21be664fcf5c42d59db07cc22c56d6;p=gnulib.git

diff --git a/tests/nap.h b/tests/nap.h
index 6dfb0a077..229e4d3f8 100644
--- a/tests/nap.h
+++ b/tests/nap.h
@@ -1,5 +1,5 @@
 /* Assist in file system timestamp tests.
-   Copyright (C) 2009-2012 Free Software Foundation, Inc.
+   Copyright (C) 2009-2013 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
@@ -19,49 +19,110 @@
 #ifndef GLTEST_NAP_H
 # define GLTEST_NAP_H
 
+# include <limits.h>
+# include <stdbool.h>
+
+/* File descriptor used for the witness file.  */
+static int nap_fd = -1;
+
+/* Return A - B, in ns.
+   Return 0 if the true result would be negative.
+   Return INT_MAX if the true result would be greater than INT_MAX.  */
+static int
+diff_timespec (struct timespec a, struct timespec b)
+{
+  time_t as = a.tv_sec;
+  time_t bs = b.tv_sec;
+  int ans = a.tv_nsec;
+  int bns = b.tv_nsec;
+
+  if (! (bs < as || (bs == as && bns < ans)))
+    return 0;
+  if (as - bs <= INT_MAX / 1000000000)
+    {
+      int sdiff = (as - bs) * 1000000000;
+      int usdiff = ans - bns;
+      if (usdiff < INT_MAX - sdiff)
+        return sdiff + usdiff;
+    }
+  return INT_MAX;
+}
+
+static void
+get_stat (int fd, struct stat *st, int do_write)
+{
+  if (do_write)
+    ASSERT (write (fd, "\n", 1) == 1);
+  ASSERT (fstat (fd, st) == 0);
+}
+
+/* Given a file whose descriptor is FD, see whether delaying by DELAY
+   nanoseconds causes a change in a file's ctime and mtime.
+   OLD_ST is the file's status, recently gotten.  */
+static bool
+nap_works (int fd, int delay, struct stat old_st)
+{
+  struct stat st;
+  struct timespec delay_spec;
+  delay_spec.tv_sec = delay / 1000000000;
+  delay_spec.tv_nsec = delay % 1000000000;
+  ASSERT (nanosleep (&delay_spec, 0) == 0);
+  get_stat (fd, &st, 1);
+
+  if (   diff_timespec (get_stat_ctime (&st), get_stat_ctime (&old_st))
+      && diff_timespec (get_stat_mtime (&st), get_stat_mtime (&old_st)))
+    return true;
+
+  return false;
+}
+
+#define TEMPFILE BASE "nap.tmp"
+
+static void
+clear_temp_file (void)
+{
+  if (0 <= nap_fd)
+    {
+      ASSERT (close (nap_fd) != -1);
+      ASSERT (unlink (TEMPFILE) != -1);
+    }
+}
+
 /* Sleep long enough to notice a timestamp difference on the file
-   system in the current directory.  Assumes that BASE is defined,
-   and requires that the test module depends on usleep.  */
+   system in the current directory.  Use an adaptive approach, trying
+   to find the smallest delay which works on the current file system
+   to make the timestamp difference appear.  Assert a maximum delay of
+   ~2 seconds, more precisely sum(2^n) from 0 to 30 = 2^31 - 1 = 2.1s.
+   Assumes that BASE is defined, and requires that the test module
+   depends on nanosleep.  */
 static void
 nap (void)
 {
-  static long delay;
-  if (!delay)
+  struct stat old_st;
+  static int delay = 1;
+
+  if (-1 == nap_fd)
+    {
+      atexit (clear_temp_file);
+      ASSERT ((nap_fd = creat (TEMPFILE, 0600)) != -1);
+      get_stat (nap_fd, &old_st, 0);
+    }
+  else
     {
-      /* Initialize only once, by sleeping for 20 milliseconds (needed
-         since xfs has a quantization of about 10 milliseconds, even
-         though it has a granularity of 1 nanosecond, and since NTFS
-         has a default quantization of 15.25 milliseconds, even though
-         it has a granularity of 100 nanoseconds).  If the seconds
-         differ, repeat the test one more time (in case we crossed a
-         quantization boundary on a file system with 1 second
-         resolution).  If we can't observe a difference in only the
-         nanoseconds, then fall back to 1 second if the time is odd,
-         and 2 seconds (needed for FAT) if time is even.  */
-      struct stat st1;
-      struct stat st2;
-      ASSERT (close (creat (BASE "tmp", 0600)) == 0);
-      ASSERT (stat (BASE "tmp", &st1) == 0);
-      ASSERT (unlink (BASE "tmp") == 0);
-      delay = 20000;
-      usleep (delay);
-      ASSERT (close (creat (BASE "tmp", 0600)) == 0);
-      ASSERT (stat (BASE "tmp", &st2) == 0);
-      ASSERT (unlink (BASE "tmp") == 0);
-      if (st1.st_mtime != st2.st_mtime)
-        {
-          /* Seconds differ, give it one more shot.  */
-          st1 = st2;
-          usleep (delay);
-          ASSERT (close (creat (BASE "tmp", 0600)) == 0);
-          ASSERT (stat (BASE "tmp", &st2) == 0);
-          ASSERT (unlink (BASE "tmp") == 0);
-        }
-      if (! (st1.st_mtime == st2.st_mtime
-             && get_stat_mtime_ns (&st1) < get_stat_mtime_ns (&st2)))
-        delay = (st1.st_mtime & 1) ? 1000000 : 2000000;
+      ASSERT (0 <= nap_fd);
+      get_stat (nap_fd, &old_st, 1);
     }
-  usleep (delay);
+
+  if (1 < delay)
+    delay = delay / 2;  /* Try half of the previous delay.  */
+  ASSERT (0 < delay);
+
+  for ( ; delay <= 2147483647; delay = delay * 2)
+    if (nap_works (nap_fd, delay, old_st))
+      return;
+
+  /* Bummer: even the highest nap delay didn't work. */
+  ASSERT (0);
 }
 
 #endif /* GLTEST_NAP_H */