gnulib support for st_birthtime (second revision of patch)

[James Youngman]

Tested on:
        Linux (ext3) (no st_birthtime support at all)
        NetBSD-3.1 (UFS1) (st_birthtime support in kernel but not filesystem)
        NetBSD-3.1 (UFS2) (st_birthtime support both kernel and filesystem)
        NetBSD-3.1 (msdos) (st_birthtime support in kernel but not in 
filesystem)
        
Needs testing on everything else, notably including:
        Cygwin CVS (i.e. version 1.7 or later)
        mingw
        Systems completely lacking nanosecond timestamps

Style issue:
        The test case perhaps should not ASSERT that the test 
        files can be created.   It should arguably skip the test 
        withough failing if that happens.


2007-03-27  James Youngman  <address@hidden>

       * lib/stat-time.h (get_stat_birthtime): New function for
         retrieving st_birthtime as provided by UFS2 (hence *BSD).
       * m4/stat-time.m4 (gl_STAT_BIRTHTIME): Probe for st_birthtime
         and its variants.
       * modules/stat-time (configure.ac): call gl_STAT_BIRTHTIME.
       * modules/stat-time-test: New test
       * tests/test-stat-time.c: New test, devised by Bruno Haible.


Index: lib/stat-time.h
===================================================================
RCS file: /sources/gnulib/gnulib/lib/stat-time.h,v
retrieving revision 1.4
diff -u -p -r1.4 stat-time.h
--- lib/stat-time.h     23 Feb 2007 18:25:21 -0000      1.4
+++ lib/stat-time.h     27 Mar 2007 08:06:22 -0000
@@ -44,6 +44,13 @@
 # define STAT_TIMESPEC_NS(st, st_xtim) ((st)->st_xtim.st__tim.tv_nsec)
 #endif
 
+#if defined(HAVE_STRUCT_STAT_ST_BIRTHTIME) || 
defined(HAVE_STRUCT_STAT_ST_BIRTHTIMENSEC) || 
defined(HAVE_STRUCT_STAT_ST_BIRTHTIMESPEC_TV_NSEC) || 
defined(HAVE_STRUCT_STAT_ST_SPARE4)
+# define USE_BIRTHTIME 1
+#else
+# undef USE_BIRTHTIME
+#endif
+
+
 /* Return the nanosecond component of *ST's access time.  */
 static inline long int
 get_stat_atime_ns (struct stat const *st)
@@ -89,6 +96,28 @@ get_stat_mtime_ns (struct stat const *st
 # endif
 }
 
+/* Return the nanosecond component of *ST's birth time.  */
+static inline long int
+get_stat_birthtime_ns (struct stat const *st)
+{
+# if defined USE_BIRTHTIME
+#  if defined(STAT_TIMESPEC) && 
defined(HAVE_STRUCT_STAT_ST_BIRTHTIMESPEC_TV_NSEC)
+  return STAT_TIMESPEC (st, st_birthtim).tv_nsec;
+#  elif defined(STAT_TIMESPEC_NS) && 
defined(HAVE_STRUCT_STAT_ST_BIRTHTIMESPEC_TV_SEC)
+  return STAT_TIMESPEC_NS (st, st_birthtim);
+#  elif defined HAVE_STRUCT_STAT_ST_SPARE4
+  /* Cygwin, without __CYGWIN_USE_BIG_TYPES__ */
+  return st->st_spare4[1] * 1000L;
+#  else
+  /* Birthtime is available, but not at nanosecond resolution. */
+  return 0;
+#  endif
+# else
+  /* birthtime is not available, so indicate this in the returned value */
+  return 0;
+# endif 
+}
+
 /* Return *ST's access time.  */
 static inline struct timespec
 get_stat_atime (struct stat const *st)
@@ -131,4 +160,69 @@ get_stat_mtime (struct stat const *st)
 #endif
 }
 
+/* Return *ST's birth time, if available, in *PTS.  A nonzero value is
+ * returned if the stat structure appears to indicate that the
+ * timestamp is available.
+ *
+ * The return value of this function does not reliably indicate that the 
+ * returned data is valid; see the comments within the body of the 
+ * function for an explanation.
+ */
+static inline int
+get_stat_birthtime (struct stat const *st,
+                   struct timespec *pts)
+{
+#if defined USE_BIRTHTIME
+# ifdef STAT_TIMESPEC
+  *pts = STAT_TIMESPEC (st, st_birthtim);
+# else
+  struct timespec t;
+  pts->tv_sec = st->st_birthtime;
+  pts->tv_nsec = get_stat_birthtime_ns (st);
+# endif
+
+  /* NetBSD sometimes signals the absence of knowledge of the file's
+   * birth time by using zero.  We indicate we don't know, by
+   * returning 0 from this function when that happens.  This is
+   * slightly problematic since (time_t)0 is otherwise a valid, albeit
+   * unlikely, timestamp.  
+   *
+   * NetBSD sometimes returns 0 for unknown values (for example on
+   * ffs) and sometimes begative values for tv_nsec (for example on
+   * NFS).  For some filesystems (e.g. msdos) NetBSD also appears to
+   * fail to update the st_birthtime member at all, and just leaves in
+   * there whatever junk existed int he uninitialised stat structure
+   * the caller provided.  Therefore, callers are advised to initialise
+   * the tv_nsec number to a negative value before they call stat in
+   * order to detect this problem.
+   */
+  if (pts->tv_sec == (time_t)0)
+    {
+      return 0;                        /* result probably invalid, see above. 
*/
+    }
+  else
+    {
+      /* Sometimes NetBSD returns junk in the birth time fields, so 
+       * do a simple range check on the data, and return 0 to indicate
+       * that the data is invalid if it just looks wrong. 
+       */
+      return (pts->tv_nsec >= 0) && (pts->tv_nsec <= 1000000000);
+    }
+#elif (defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__
+  /* Woe32 native platforms (mingw, msvc, but not Cygwin) put the
+   * "file creation time" in st_ctime (!).  See for example the
+   * article
+   * http://msdn2.microsoft.com/de-de/library/14h5k7ff(VS.80).aspx
+   */
+  pts->tv_sec = st->st_ctime;
+  pts->tv_nsec = 0;
+  return 1;                    /* result is valid */
+#else
+  /* Birth time not supported. */
+  pts->tv_sec = 0;
+  pts->tv_nsec = 0;
+  return 0;                    /* result is not valid */
+#endif
+}
+
 #endif
Index: m4/stat-time.m4
===================================================================
RCS file: /sources/gnulib/gnulib/m4/stat-time.m4,v
retrieving revision 1.4
diff -u -p -r1.4 stat-time.m4
--- m4/stat-time.m4     18 Jan 2007 08:33:35 -0000      1.4
+++ m4/stat-time.m4     27 Mar 2007 08:06:22 -0000
@@ -10,11 +10,13 @@
 dnl From Paul Eggert.
 
 # st_atim.tv_nsec - Linux, Solaris
-# st_atimespec.tv_nsec - FreeBSD, if ! defined _POSIX_SOURCE
-# st_atimensec - FreeBSD, if defined _POSIX_SOURCE
+# st_atimespec.tv_nsec - FreeBSD, NetBSD, if ! defined _POSIX_SOURCE
+# st_atimensec - FreeBSD, NetBSD, if defined _POSIX_SOURCE
 # st_atim.st__tim.tv_nsec - UnixWare (at least 2.1.2 through 7.1)
 # st_spare1 - Cygwin?
 
+# st_birthtimespec present on NetBSD (probably also FreBSD, OpenBSD)
+
 AC_DEFUN([gl_STAT_TIME],
 [
   AC_REQUIRE([AC_C_INLINE])
@@ -61,3 +63,26 @@ AC_DEFUN([gl_STAT_TIME],
     [#include <sys/types.h>
      #include <sys/stat.h>])
 ])
+
+# Checks for st_birthtime, which is a feature from UFS2 (FreeBSD, NetBSD, 
OpenBSD, etc.)
+# There was a time when this field was named st_createtime (21 June 2002 to 16 
July 2002)
+# But that window is very small and applied only to development code, so 
systems still
+# using that configuration are not a realistic development target.
+# See revisions 1.10 and 1.11 of FreeBSD's src/sys/ufs/ufs/dinode.h.
+#
+AC_DEFUN([gl_STAT_BIRTHTIME],
+[
+  AC_REQUIRE([AC_C_INLINE])
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_CHECK_HEADERS_ONCE([sys/time.h])
+  AC_CHECK_MEMBERS([struct stat.st_birthtimespec.tv_sec, struct 
stat.st_birthtimespec.tv_nsec], [],
+    [AC_CHECK_MEMBERS([struct stat.st_birthtime, struct 
stat.st_birthtimensec], [], 
+       [AC_CHECK_MEMBERS([struct stat.st_spare4], [], 
+          [],
+          [#include <sys/types.h>
+           #include <sys/stat.h>])],
+       [#include <sys/types.h>
+       #include <sys/stat.h>])],
+    [#include <sys/types.h>
+     #include <sys/stat.h>])
+])
Index: modules/stat-time
===================================================================
RCS file: /sources/gnulib/gnulib/modules/stat-time,v
retrieving revision 1.4
diff -u -p -r1.4 stat-time
--- modules/stat-time   12 Feb 2007 18:49:19 -0000      1.4
+++ modules/stat-time   27 Mar 2007 08:06:22 -0000
@@ -10,6 +10,7 @@ time
 
 configure.ac:
 gl_STAT_TIME
+gl_STAT_BIRTHTIME
 
 Makefile.am:
 
===================================================================
--- /dev/null   2007-03-26 11:36:11.944059000 +0100
+++ modules/stat-time-tests     2007-03-26 00:49:57.000000000 +0100
@@ -0,0 +1,11 @@
+Files:
+tests/test-stat-time.c
+
+Depends-on:
+time
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-stat-time
+check_PROGRAMS += test-stat-time
===================================================================
--- /dev/null   2007-03-26 11:36:11.944059000 +0100
+++ tests/test-stat-time.c      2007-03-26 02:02:39.000000000 +0100
@@ -0,0 +1,160 @@
+/* Test of <stat-time.h>.
+   Copyright (C) 2007 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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by James Youngman <address@hidden>, 2007.  */
+
+#include <config.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/fcntl.h>
+
+#include "stat-time.h"
+
+enum { NFILES = 5 };
+
+
+
+#define ASSERT(condition) if (!(condition)) abort ()
+
+static int
+open_file(const char *filename, int flags)
+{
+  int fd = open(filename, flags|O_WRONLY, 0500);
+  if (fd >= 0)
+    {
+      close(fd);
+      return 1;
+    }
+  else
+    {
+      return 0;
+    }
+}
+
+static void
+create_file(const char *filename)
+{
+  ASSERT(open_file(filename, O_CREAT|O_EXCL));
+}
+
+
+static int
+touch_file(const char *filename)
+{
+  ASSERT(open_file(filename, O_CREAT));
+}
+
+static void
+do_stat(const char *filename, struct stat *p)
+{
+  ASSERT(0 == stat(filename, p));
+}
+
+
+static int 
+prepare_test(struct stat *statinfo, struct timespec *modtimes)
+{
+  int i;
+  
+  create_file("stamp1");
+  sleep(2);
+  create_file("testfile");
+  sleep(2);
+  create_file("stamp2");
+  sleep(2);
+  ASSERT(0 == rename("testfile", "renamed"));
+  sleep(2);
+  create_file("stamp3");
+  
+  do_stat("stamp1",  &statinfo[0]);
+  do_stat("renamed", &statinfo[1]);
+  do_stat("stamp2",  &statinfo[2]);
+  do_stat("stamp3",  &statinfo[3]);
+  
+  /* Now use our access functions. */
+  for (i=0; i<NFILES; ++i)
+    {
+      modtimes[i] = get_stat_mtime(&statinfo[i]);
+    }
+}
+
+
+static void
+test_mtime(const struct stat *statinfo, struct timespec *modtimes)
+{
+  int i;
+  
+  /* Use the struct stat fields directly. */
+  ASSERT(statinfo[0].st_mtime < statinfo[2].st_mtime); /* mtime(stamp1) < 
mtime(stamp2) */
+  ASSERT(statinfo[2].st_mtime < statinfo[3].st_mtime); /* mtime(stamp2) < 
mtime(stamp3) */
+  ASSERT(statinfo[2].st_mtime < statinfo[1].st_ctime); /* mtime(stamp2) < 
ctime(renamed) */
+
+  /* Now check the result of the access functions. */
+  ASSERT(modtimes[0].tv_sec < modtimes[2].tv_sec); /* mtime(stamp1) < 
mtime(stamp2) */
+  ASSERT(modtimes[2].tv_sec < modtimes[3].tv_sec); /* mtime(stamp2) < 
mtime(stamp3) */
+
+  /* verify equivalence */
+  for (i=0; i<NFILES; ++i)
+    {
+      struct timespec ts;
+      ts = get_stat_mtime(&statinfo[i]);
+      ASSERT(ts.tv_sec == statinfo[i].st_mtime);
+    }
+
+  ASSERT(statinfo[2].st_mtime < statinfo[1].st_ctime); /* mtime(stamp2) < 
ctime(renamed) */
+}
+
+
+static int
+test_birthtime(const struct stat *statinfo,
+              const struct timespec *modtimes,
+              struct timespec *birthtimes)
+{
+  int i;
+  
+  /* Collect the birth times.. */
+  for (i=0; i<NFILES; ++i)
+    {
+      if (1 || !get_stat_birthtime(&statinfo[i], &birthtimes[i]))
+       {
+         return 0;
+       }
+    }
+  
+  ASSERT(modtimes[0].tv_sec < birthtimes[1].tv_sec); /* mtime(stamp1) < 
birthtime(renamed) */
+  ASSERT(birthtimes[1].tv_sec < modtimes[2].tv_sec); /* birthtime(renamed) < 
mtime(stamp2) */
+}
+
+int
+main ()
+{
+  int skipflag = 0;
+  struct stat statinfo[NFILES];
+  struct timespec modtimes[NFILES];
+  struct timespec birthtimes[NFILES];
+
+  prepare_test(statinfo, modtimes);
+  test_mtime    (statinfo, modtimes);
+  if (!test_birthtime(statinfo, modtimes, birthtimes))
+    skipflag = 1;
+  
+  unlink("stamp1");
+  unlink("renamed");
+  unlink("stamp2");
+  unlink("stamp3");
+  return 0;
+}


-- 
James Youngman
Dublin, Ireland