4 files changed, 1460 insertions, 0 deletions

diff --git a/DotLock.hs b/DotLock.hs
new file mode 100644
index 0000000..257a033
--- /dev/null
+++ b/DotLock.hs
@@ -0,0 +1,44 @@
+module DotLock 
+    ( DotLock
+    , Flags
+    , dotlock_init
+    , dotlock_create
+    , dotlock_take
+    , dotlock_release
+    , dotlock_destroy
+    , dotlock_remove_lockfiles
+    , dotlock_set_fd
+    , dotlock_get_fd
+    , dotlock_disable
+    ) where
+
+import System.Posix.Types (Fd(..))
+import Foreign.C.String
+import Foreign.C.Types
+import Foreign.Ptr
+
+newtype DotLock = DotLockPtr (Ptr ())
+type Flags = Int
+
+foreign import ccall "dotlock_create" _dotlock_create_ptr :: Ptr Char -> Flags -> IO (Ptr ())
+
+foreign import ccall "dotlock_create" _dotlock_create :: CString -> Flags -> IO (Ptr ())
+
+dotlock_init :: IO ()
+dotlock_init = do
+    null_ptr <- _dotlock_create_ptr nullPtr 0
+    return ()
+
+dotlock_create :: FilePath -> Flags -> IO (Maybe DotLock)
+dotlock_create file flags = do
+    ptr <- withCString file (flip _dotlock_create flags)
+    if ptr == nullPtr then return Nothing else return (Just $ DotLockPtr ptr)
+      
+
+foreign import ccall "dotlock_take" dotlock_take :: DotLock -> CLong -> IO CInt
+foreign import ccall "dotlock_release" dotlock_release :: DotLock -> IO CInt
+foreign import ccall "dotlock_destroy" dotlock_destroy :: DotLock -> IO ()
+foreign import ccall "dotlock_remove_lockfiles" dotlock_remove_lockfiles ::DotLock -> IO ()
+foreign import ccall "dotlock_set_fd" dotlock_set_fd :: DotLock -> Fd -> IO ()
+foreign import ccall "dotlock_get_fd" dotlock_get_fd :: DotLock -> IO Fd
+foreign import ccall "dotlock_disable" dotlock_disable :: IO ()
diff --git a/dotlock.c b/dotlock.c
new file mode 100644
index 0000000..c111159
--- /dev/null
+++ b/dotlock.c
@@ -0,0 +1,1303 @@
+/* dotlock.c - dotfile locking
+ * Copyright (C) 1998, 2000, 2001, 2003, 2004,
+ *               2005, 2006, 2008, 2010, 2011 Free Software Foundation, Inc.
+ *
+ * This file is part of JNLIB, which is a subsystem of GnuPG.
+ *
+ * JNLIB is free software; you can redistribute it and/or modify it
+ * under the terms of either
+ *
+ *   - the GNU Lesser General Public License as published by the Free
+ *     Software Foundation; either version 3 of the License, or (at
+ *     your option) any later version.
+ *
+ * or
+ *
+ *   - the GNU General Public License as published by the Free
+ *     Software Foundation; either version 2 of the License, or (at
+ *     your option) any later version.
+ *
+ * or both in parallel, as here.
+ *
+ * JNLIB 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 copies of the GNU General Public License
+ * and the GNU Lesser General Public License along with this program;
+ * if not, see <http://www.gnu.org/licenses/>.
+ *
+ * ALTERNATIVELY, this file may be distributed under the terms of the
+ * following license, in which case the provisions of this license are
+ * required INSTEAD OF the GNU Lesser General License or the GNU
+ * General Public License. If you wish to allow use of your version of
+ * this file only under the terms of the GNU Lesser General License or
+ * the GNU General Public License, and not to allow others to use your
+ * version of this file under the terms of the following license,
+ * indicate your decision by deleting this paragraph and the license
+ * below.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, and the entire permission notice in its entirety,
+ *    including the disclaimer of warranties.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+   Overview:
+   =========
+
+   This module implements advisory file locking in a portable way.
+   Due to the problems with POSIX fcntl locking a separate lock file
+   is used.  It would be possible to use fcntl locking on this lock
+   file and thus avoid the weird auto unlock bug of POSIX while still
+   having an unproved better performance of fcntl locking.  However
+   there are still problems left, thus we resort to use a hardlink
+   which has the well defined property that a link call will fail if
+   the target file already exists.
+
+   Given that hardlinks are also available on NTFS file systems since
+   Windows XP; it will be possible to enhance this module to use
+   hardlinks even on Windows and thus allow Windows and Posix clients
+   to use locking on the same directory.  This is not yet implemented;
+   instead we use a lockfile on Windows along with W32 style file
+   locking.
+
+   On FAT file systems hardlinks are not supported.  Thus this method
+   does not work.  Our solution is to use a O_EXCL locking instead.
+   Querying the type of the file system is not easy to do in a
+   portable way (e.g. Linux has a statfs, BSDs have a the same call
+   but using different structures and constants).  What we do instead
+   is to check at runtime whether link(2) works for a specific lock
+   file.
+
+
+   How to use:
+   ===========
+
+   At program initialization time, the module should be explicitly
+   initialized:
+
+      dotlock_create (NULL, 0);
+
+   This installs an atexit handler and may also initialize mutex etc.
+   It is optional for non-threaded applications.  Only the first call
+   has an effect.  This needs to be done before any extra threads are
+   started.
+
+   To create a lock file (which  prepares it but does not take the
+   lock) you do:
+
+     dotlock_t h
+
+     h = dotlock_create (fname, 0);
+     if (!h)
+       error ("error creating lock file: %s\n", strerror (errno));
+
+   It is important to handle the error.  For example on a read-only
+   file system a lock can't be created (but is usually not needed).
+   FNAME is the file you want to lock; the actual lockfile is that
+   name with the suffix ".lock" appended.  On success a handle to be
+   used with the other functions is returned or NULL on error.  Note
+   that the handle shall only be used by one thread at a time.  This
+   function creates a unique file temporary file (".#lk*") in the same
+   directory as FNAME and returns a handle for further operations.
+   The module keeps track of theses unique files so that they will be
+   unlinked using the atexit handler.  If you don't need the lock file
+   anymore, you may also explicitly remove it with a call to:
+
+     dotlock_destroy (h);
+
+   To actually lock the file, you use:
+
+     if (dotlock_take (h, -1))
+       error ("error taking lock: %s\n", strerror (errno));
+
+   This function will wait until the lock is acquired.  If an
+   unexpected error occurs if will return non-zero and set ERRNO.  If
+   you pass (0) instead of (-1) the function does not wait in case the
+   file is already locked but returns -1 and sets ERRNO to EACCES.
+   Any other positive value for the second parameter is considered a
+   timeout valuie in milliseconds.
+
+   To release the lock you call:
+
+     if (dotlock_release (h))
+       error ("error releasing lock: %s\n", strerror (errno));
+
+   or, if the lock file is not anymore needed, you may just call
+   dotlock_destroy.  However dotlock_release does some extra checks
+   before releasing the lock and prints diagnostics to help detecting
+   bugs.
+
+   If you want to explicitly destroy all lock files you may call
+
+     dotlock_remove_lockfiles ();
+
+   which is the core of the installed atexit handler.  In case your
+   application wants to disable locking completely it may call
+
+     disable_locking ()
+
+   before any locks are created.
+
+   There are two convenience functions to store an integer (e.g. a
+   file descriptor) value with the handle:
+
+     void dotlock_set_fd (dotlock_t h, int fd);
+     int  dotlock_get_fd (dotlock_t h);
+
+   If nothing has been stored dotlock_get_fd returns -1.
+
+
+
+   How to build:
+   =============
+
+   This module was originally developed for GnuPG but later changed to
+   allow its use without any GnuPG dependency.  If you want to use it
+   with you application you may simply use it and it should figure out
+   most things automagically.
+
+   You may use the common config.h file to pass macros, but take care
+   to pass -DHAVE_CONFIG_H to the compiler.  Macros used by this
+   module are:
+
+     DOTLOCK_USE_PTHREAD  - Define if POSIX threads are in use.
+
+     DOTLOCK_GLIB_LOGGING - Define this to use Glib logging functions.
+
+     DOTLOCK_EXT_SYM_PREFIX - Prefix all external symbols with the
+                              string to which this macro evaluates.
+
+     GNUPG_MAJOR_VERSION - Defined when used by GnuPG.
+
+     HAVE_DOSISH_SYSTEM  - Defined for Windows etc.  Will be
+                           automatically defined if a the target is
+                           Windows.
+
+     HAVE_POSIX_SYSTEM   - Internally defined to !HAVE_DOSISH_SYSTEM.
+
+     HAVE_SIGNAL_H       - Should be defined on Posix systems.  If config.h
+                           is not used defaults to defined.
+
+     DIRSEP_C            - Separation character for file name parts.
+                           Usually not redefined.
+
+     EXTSEP_S            - Separation string for file name suffixes.
+                           Usually not redefined.
+
+     HAVE_W32CE_SYSTEM   - Currently only used by GnuPG.
+
+   Note that there is a test program t-dotlock which has compile
+   instructions at its end.  At least for SMBFS and CIFS it is
+   important that 64 bit versions of stat are used; most programming
+   environments do this these days, just in case you want to compile
+   it on the command line, remember to pass -D_FILE_OFFSET_BITS=64
+
+
+   Bugs:
+   =====
+
+   On Windows this module is not yet thread-safe.
+
+
+   Miscellaneous notes:
+   ====================
+
+   On hardlinks:
+   - Hardlinks are supported under Windows with NTFS since XP/Server2003.
+   - In Linux 2.6.33 both SMBFS and CIFS seem to support hardlinks.
+   - NFS supports hard links.  But there are solvable problems.
+   - FAT does not support links
+
+   On the file locking API:
+   - CIFS on Linux 2.6.33 supports several locking methods.
+     SMBFS seems not to support locking.  No closer checks done.
+   - NFS supports Posix locks.  flock is emulated in the server.
+     However there are a couple of problems; see below.
+   - FAT does not support locks.
+   - An advantage of fcntl locking is that R/W locks can be
+     implemented which is not easy with a straight lock file.
+
+   On O_EXCL:
+   - Does not work reliable on NFS
+   - Should work on CIFS and SMBFS but how can we delete lockfiles?
+
+   On NFS problems:
+   - Locks vanish if the server crashes and reboots.
+   - Client crashes keep the lock in the server until the client
+     re-connects.
+   - Communication problems may return unreliable error codes.  The
+     MUA Postfix's workaround is to compare the link count after
+     seeing an error for link.  However that gives a race.  If using a
+     unique file to link to a lockfile and using stat to check the
+     link count instead of looking at the error return of link(2) is
+     the best solution.
+   - O_EXCL seems to have a race and may re-create a file anyway.
+
+*/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+/* Some quick replacements for stuff we usually expect to be defined
+   in config.h.  Define HAVE_POSIX_SYSTEM for better readability. */
+#if !defined (HAVE_DOSISH_SYSTEM) && defined(_WIN32)
+# define HAVE_DOSISH_SYSTEM 1
+#endif
+#if !defined (HAVE_DOSISH_SYSTEM) && !defined (HAVE_POSIX_SYSTEM)
+# define HAVE_POSIX_SYSTEM 1
+#endif
+
+/* With no config.h assume that we have sitgnal.h.  */
+#if !defined (HAVE_CONFIG_H) && defined (HAVE_POSIX_SYSTEM)
+# define HAVE_SIGNAL_H 1
+#endif
+
+/* Standard headers.  */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <errno.h>
+#include <unistd.h>
+#ifdef  HAVE_DOSISH_SYSTEM
+# define WIN32_LEAN_AND_MEAN  /* We only need the OS core stuff.  */
+# include <windows.h>
+#else
+# include <sys/types.h>
+# include <sys/stat.h>
+# include <sys/utsname.h>
+#endif
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#ifdef HAVE_SIGNAL_H
+# include <signal.h>
+#endif
+#ifdef DOTLOCK_USE_PTHREAD
+# include <pthread.h>
+#endif
+
+#ifdef DOTLOCK_GLIB_LOGGING
+# include <glib.h>
+#endif
+
+#ifdef GNUPG_MAJOR_VERSION
+# include "libjnlib-config.h"
+#endif
+#ifdef HAVE_W32CE_SYSTEM
+# include "utf8conv.h"  /* WindowsCE requires filename conversion.  */
+#endif
+
+#include "dotlock.h"
+
+
+/* Define constants for file name construction.  */
+#if !defined(DIRSEP_C) && !defined(EXTSEP_S)
+# ifdef HAVE_DOSISH_SYSTEM
+#  define DIRSEP_C '\\'
+#  define EXTSEP_S "."
+#else
+#  define DIRSEP_C '/'
+#  define EXTSEP_S "."
+# endif
+#endif
+
+/* In GnuPG we use wrappers around the malloc fucntions.  If they are
+   not defined we assume that this code is used outside of GnuPG and
+   fall back to the regular malloc functions.  */
+#ifndef jnlib_malloc
+# define jnlib_malloc(a)     malloc ((a))
+# define jnlib_calloc(a,b)   calloc ((a), (b))
+# define jnlib_free(a)       free ((a))
+#endif
+
+/* Wrapper to set ERRNO.  */
+#ifndef jnlib_set_errno
+# ifdef HAVE_W32CE_SYSTEM
+#  define jnlib_set_errno(e)  gpg_err_set_errno ((e))
+# else
+#  define jnlib_set_errno(e)  do { errno = (e); } while (0)
+# endif
+#endif
+
+/* Gettext macro replacement.  */
+#ifndef _
+# define _(a) (a)
+#endif
+
+#ifdef GNUPG_MAJOR_VERSION
+# define my_info_0(a)       log_info ((a))
+# define my_info_1(a,b)     log_info ((a), (b))
+# define my_info_2(a,b,c)   log_info ((a), (b), (c))
+# define my_info_3(a,b,c,d) log_info ((a), (b), (c), (d))
+# define my_error_0(a)      log_error ((a))
+# define my_error_1(a,b)    log_error ((a), (b))
+# define my_error_2(a,b,c)  log_error ((a), (b), (c))
+# define my_debug_1(a,b)    log_debug ((a), (b))
+# define my_fatal_0(a)      log_fatal ((a))
+#elif defined (DOTLOCK_GLIB_LOGGING)
+# define my_info_0(a)       g_message ((a))
+# define my_info_1(a,b)     g_message ((a), (b))
+# define my_info_2(a,b,c)   g_message ((a), (b), (c))
+# define my_info_3(a,b,c,d) g_message ((a), (b), (c), (d))
+# define my_error_0(a)      g_warning ((a))
+# define my_error_1(a,b)    g_warning ((a), (b))
+# define my_error_2(a,b,c)  g_warning ((a), (b), (c))
+# define my_debug_1(a,b)    g_debug ((a), (b))
+# define my_fatal_0(a)      g_error ((a))
+#else
+# define my_info_0(a)       fprintf (stderr, (a))
+# define my_info_1(a,b)     fprintf (stderr, (a), (b))
+# define my_info_2(a,b,c)   fprintf (stderr, (a), (b), (c))
+# define my_info_3(a,b,c,d) fprintf (stderr, (a), (b), (c), (d))
+# define my_error_0(a)      fprintf (stderr, (a))
+# define my_error_1(a,b)    fprintf (stderr, (a), (b))
+# define my_error_2(a,b,c)  fprintf (stderr, (a), (b), (c))
+# define my_debug_1(a,b)    fprintf (stderr, (a), (b))
+# define my_fatal_0(a)      do { fprintf (stderr,(a)); fflush (stderr); \
+                                 abort (); } while (0)
+#endif
+
+
+
+
+
+/* The object describing a lock.  */
+struct dotlock_handle
+{
+  struct dotlock_handle *next;
+  char *lockname;            /* Name of the actual lockfile.          */
+  unsigned int locked:1;     /* Lock status.                          */
+  unsigned int disable:1;    /* If true, locking is disabled.         */
+  unsigned int use_o_excl:1; /* Use open (O_EXCL) for locking.        */
+
+  int extra_fd;              /* A place for the caller to store an FD.  */
+
+#ifdef HAVE_DOSISH_SYSTEM
+  HANDLE lockhd;       /* The W32 handle of the lock file.      */
+#else /*!HAVE_DOSISH_SYSTEM */
+  char *tname;         /* Name of the lockfile template.        */
+  size_t nodename_off; /* Offset in TNAME of the nodename part. */
+  size_t nodename_len; /* Length of the nodename part.          */
+#endif /*!HAVE_DOSISH_SYSTEM */
+};
+
+
+/* A list of of all lock handles.  The volatile attribute might help
+   if used in an atexit handler.  */
+static volatile dotlock_t all_lockfiles;
+#ifdef DOTLOCK_USE_PTHREAD
+static pthread_mutex_t all_lockfiles_mutex = PTHREAD_MUTEX_INITIALIZER;
+# define LOCK_all_lockfiles() do {                               \
+        if (pthread_mutex_lock (&all_lockfiles_mutex))           \
+          my_fatal_0 ("locking all_lockfiles_mutex failed\n");   \
+      } while (0)
+# define UNLOCK_all_lockfiles() do {                             \
+        if (pthread_mutex_unlock (&all_lockfiles_mutex))         \
+          my_fatal_0 ("unlocking all_lockfiles_mutex failed\n"); \
+      } while (0)
+#else  /*!DOTLOCK_USE_PTHREAD*/
+# define LOCK_all_lockfiles()   do { } while (0)
+# define UNLOCK_all_lockfiles() do { } while (0)
+#endif /*!DOTLOCK_USE_PTHREAD*/
+
+/* If this has the value true all locking is disabled.  */
+static int never_lock;
+
+
+
+
+
+/* Entirely disable all locking.  This function should be called
+   before any locking is done.  It may be called right at startup of
+   the process as it only sets a global value.  */
+void
+dotlock_disable (void)
+{
+  never_lock = 1;
+}
+
+
+#ifdef HAVE_POSIX_SYSTEM
+static int
+maybe_deadlock (dotlock_t h)
+{
+  dotlock_t r;
+  int res = 0;
+
+  LOCK_all_lockfiles ();
+  for (r=all_lockfiles; r; r = r->next)
+    {
+      if ( r != h && r->locked )
+        {
+          res = 1;
+          break;
+        }
+    }
+  UNLOCK_all_lockfiles ();
+  return res;
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+/* Read the lock file and return the pid, returns -1 on error.  True
+   will be stored in the integer at address SAME_NODE if the lock file
+   has been created on the same node. */
+#ifdef HAVE_POSIX_SYSTEM
+static int
+read_lockfile (dotlock_t h, int *same_node )
+{
+  char buffer_space[10+1+70+1]; /* 70 is just an estimated value; node
+                                   names are usually shorter. */
+  int fd;
+  int pid = -1;
+  char *buffer, *p;
+  size_t expected_len;
+  int res, nread;
+
+  *same_node = 0;
+  expected_len = 10 + 1 + h->nodename_len + 1;
+  if ( expected_len >= sizeof buffer_space)
+    {
+      buffer = jnlib_malloc (expected_len);
+      if (!buffer)
+        return -1;
+    }
+  else
+    buffer = buffer_space;
+
+  if ( (fd = open (h->lockname, O_RDONLY)) == -1 )
+    {
+      int e = errno;
+      my_info_2 ("error opening lockfile '%s': %s\n",
+                 h->lockname, strerror(errno) );
+      if (buffer != buffer_space)
+        jnlib_free (buffer);
+      jnlib_set_errno (e); /* Need to return ERRNO here. */
+      return -1;
+    }
+
+  p = buffer;
+  nread = 0;
+  do
+    {
+      res = read (fd, p, expected_len - nread);
+      if (res == -1 && errno == EINTR)
+        continue;
+      if (res < 0)
+        {
+          my_info_1 ("error reading lockfile '%s'\n", h->lockname );
+          close (fd);
+          if (buffer != buffer_space)
+            jnlib_free (buffer);
+          jnlib_set_errno (0); /* Do not return an inappropriate ERRNO. */
+          return -1;
+        }
+      p += res;
+      nread += res;
+    }
+  while (res && nread != expected_len);
+  close(fd);
+
+  if (nread < 11)
+    {
+      my_info_1 ("invalid size of lockfile '%s'\n", h->lockname);
+      if (buffer != buffer_space)
+        jnlib_free (buffer);
+      jnlib_set_errno (0); /* Better don't return an inappropriate ERRNO. */
+      return -1;
+    }
+
+  if (buffer[10] != '\n'
+      || (buffer[10] = 0, pid = atoi (buffer)) == -1
+      || !pid )
+    {
+      my_error_2 ("invalid pid %d in lockfile '%s'\n", pid, h->lockname);
+      if (buffer != buffer_space)
+        jnlib_free (buffer);
+      jnlib_set_errno (0);
+      return -1;
+    }
+
+  if (nread == expected_len
+      && !memcmp (h->tname+h->nodename_off, buffer+11, h->nodename_len)
+      && buffer[11+h->nodename_len] == '\n')
+    *same_node = 1;
+
+  if (buffer != buffer_space)
+    jnlib_free (buffer);
+  return pid;
+}
+#endif /*HAVE_POSIX_SYSTEM */
+
+
+/* Check whether the file system which stores TNAME supports
+   hardlinks.  Instead of using the non-portable statsfs call which
+   differs between various Unix versions, we do a runtime test.
+   Returns: 0 supports hardlinks; 1 no hardlink support, -1 unknown
+   (test error).  */
+#ifdef HAVE_POSIX_SYSTEM
+static int
+use_hardlinks_p (const char *tname)
+{
+  char *lname;
+  struct stat sb;
+  unsigned int nlink;
+  int res;
+
+  if (stat (tname, &sb))
+    return -1;
+  nlink = (unsigned int)sb.st_nlink;
+
+  lname = jnlib_malloc (strlen (tname) + 1 + 1);
+  if (!lname)
+    return -1;
+  strcpy (lname, tname);
+  strcat (lname, "x");
+
+  /* We ignore the return value of link() because it is unreliable.  */
+  (void) link (tname, lname);
+
+  if (stat (tname, &sb))
+    res = -1;  /* Ooops.  */
+  else if (sb.st_nlink == nlink + 1)
+    res = 0;   /* Yeah, hardlinks are supported.  */
+  else
+    res = 1;   /* No hardlink support.  */
+
+  unlink (lname);
+  jnlib_free (lname);
+  return res;
+}
+#endif /*HAVE_POSIX_SYSTEM */
+
+
+
+#ifdef  HAVE_POSIX_SYSTEM
+/* Locking core for Unix.  It used a temporary file and the link
+   system call to make locking an atomic operation. */
+static dotlock_t
+dotlock_create_unix (dotlock_t h, const char *file_to_lock)
+{
+  int  fd = -1;
+  char pidstr[16];
+  const char *nodename;
+  const char *dirpart;
+  int dirpartlen;
+  struct utsname utsbuf;
+  size_t tnamelen;
+
+  snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid() );
+
+  /* Create a temporary file. */
+  if ( uname ( &utsbuf ) )
+    nodename = "unknown";
+  else
+    nodename = utsbuf.nodename;
+
+  if ( !(dirpart = strrchr (file_to_lock, DIRSEP_C)) )
+    {
+      dirpart = EXTSEP_S;
+      dirpartlen = 1;
+    }
+  else
+    {
+      dirpartlen = dirpart - file_to_lock;
+      dirpart = file_to_lock;
+    }
+
+  LOCK_all_lockfiles ();
+  h->next = all_lockfiles;
+  all_lockfiles = h;
+
+  tnamelen = dirpartlen + 6 + 30 + strlen(nodename) + 10 + 1;
+  h->tname = jnlib_malloc (tnamelen + 1);
+  if (!h->tname)
+    {
+      all_lockfiles = h->next;
+      UNLOCK_all_lockfiles ();
+      jnlib_free (h);
+      return NULL;
+    }
+  h->nodename_len = strlen (nodename);
+
+  snprintf (h->tname, tnamelen, "%.*s/.#lk%p.", dirpartlen, dirpart, h );
+  h->nodename_off = strlen (h->tname);
+  snprintf (h->tname+h->nodename_off, tnamelen - h->nodename_off,
+           "%s.%d", nodename, (int)getpid ());
+
+  do
+    {
+      jnlib_set_errno (0);
+      fd = open (h->tname, O_WRONLY|O_CREAT|O_EXCL,
+                 S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR );
+    }
+  while (fd == -1 && errno == EINTR);
+
+  if ( fd == -1 )
+    {
+      all_lockfiles = h->next;
+      UNLOCK_all_lockfiles ();
+      my_error_2 (_("failed to create temporary file '%s': %s\n"),
+                  h->tname, strerror(errno));
+      jnlib_free (h->tname);
+      jnlib_free (h);
+      return NULL;
+    }
+  if ( write (fd, pidstr, 11 ) != 11 )
+    goto write_failed;
+  if ( write (fd, nodename, strlen (nodename) ) != strlen (nodename) )
+    goto write_failed;
+  if ( write (fd, "\n", 1 ) != 1 )
+    goto write_failed;
+  if ( close (fd) )
+    goto write_failed;
+
+  /* Check whether we support hard links.  */
+  switch (use_hardlinks_p (h->tname))
+    {
+    case 0: /* Yes.  */
+      break;
+    case 1: /* No.  */
+      unlink (h->tname);
+      h->use_o_excl = 1;
+      break;
+    default:
+      my_error_2 ("can't check whether hardlinks are supported for '%s': %s\n",
+                  h->tname, strerror(errno));
+      goto write_failed;
+    }
+
+  h->lockname = jnlib_malloc (strlen (file_to_lock) + 6 );
+  if (!h->lockname)
+    {
+      all_lockfiles = h->next;
+      UNLOCK_all_lockfiles ();
+      unlink (h->tname);
+      jnlib_free (h->tname);
+      jnlib_free (h);
+      return NULL;
+    }
+  strcpy (stpcpy (h->lockname, file_to_lock), EXTSEP_S "lock");
+  UNLOCK_all_lockfiles ();
+  if (h->use_o_excl)
+    my_debug_1 ("locking for '%s' done via O_EXCL\n", h->lockname);
+
+  return h;
+
+ write_failed:
+  all_lockfiles = h->next;
+  UNLOCK_all_lockfiles ();
+  my_error_2 (_("error writing to '%s': %s\n"), h->tname, strerror (errno));
+  close (fd);
+  unlink (h->tname);
+  jnlib_free (h->tname);
+  jnlib_free (h);
+  return NULL;
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Locking core for Windows.  This version does not need a temporary
+   file but uses the plain lock file along with record locking.  We
+   create this file here so that we later only need to do the file
+   locking.  For error reporting it is useful to keep the name of the
+   file in the handle.  */
+static dotlock_t
+dotlock_create_w32 (dotlock_t h, const char *file_to_lock)
+{
+  LOCK_all_lockfiles ();
+  h->next = all_lockfiles;
+  all_lockfiles = h;
+
+  h->lockname = jnlib_malloc ( strlen (file_to_lock) + 6 );
+  if (!h->lockname)
+    {
+      all_lockfiles = h->next;
+      UNLOCK_all_lockfiles ();
+      jnlib_free (h);
+      return NULL;
+    }
+  strcpy (stpcpy(h->lockname, file_to_lock), EXTSEP_S "lock");
+
+  /* If would be nice if we would use the FILE_FLAG_DELETE_ON_CLOSE
+     along with FILE_SHARE_DELETE but that does not work due to a race
+     condition: Despite the OPEN_ALWAYS flag CreateFile may return an
+     error and we can't reliable create/open the lock file unless we
+     would wait here until it works - however there are other valid
+     reasons why a lock file can't be created and thus the process
+     would not stop as expected but spin until Windows crashes.  Our
+     solution is to keep the lock file open; that does not harm. */
+  {
+#ifdef HAVE_W32CE_SYSTEM
+    wchar_t *wname = utf8_to_wchar (h->lockname);
+
+    if (wname)
+      h->lockhd = CreateFile (wname,
+                              GENERIC_READ|GENERIC_WRITE,
+                              FILE_SHARE_READ|FILE_SHARE_WRITE,
+                              NULL, OPEN_ALWAYS, 0, NULL);
+    else
+      h->lockhd = INVALID_HANDLE_VALUE;
+    jnlib_free (wname);
+#else
+    h->lockhd = CreateFile (h->lockname,
+                            GENERIC_READ|GENERIC_WRITE,
+                            FILE_SHARE_READ|FILE_SHARE_WRITE,
+                            NULL, OPEN_ALWAYS, 0, NULL);
+#endif
+  }
+  if (h->lockhd == INVALID_HANDLE_VALUE)
+    {
+      all_lockfiles = h->next;
+      UNLOCK_all_lockfiles ();
+      my_error_2 (_("can't create '%s': %s\n"), h->lockname, w32_strerror (-1));
+      jnlib_free (h->lockname);
+      jnlib_free (h);
+      return NULL;
+    }
+  return h;
+}
+#endif /*HAVE_DOSISH_SYSTEM*/
+
+
+/* Create a lockfile for a file name FILE_TO_LOCK and returns an
+   object of type dotlock_t which may be used later to actually acquire
+   the lock.  A cleanup routine gets installed to cleanup left over
+   locks or other files used internally by the lock mechanism.
+
+   Calling this function with NULL does only install the atexit
+   handler and may thus be used to assure that the cleanup is called
+   after all other atexit handlers.
+
+   This function creates a lock file in the same directory as
+   FILE_TO_LOCK using that name and a suffix of ".lock".  Note that on
+   POSIX systems a temporary file ".#lk.<hostname>.pid[.threadid] is
+   used.
+
+   FLAGS must be 0.
+
+   The function returns an new handle which needs to be released using
+   destroy_dotlock but gets also released at the termination of the
+   process.  On error NULL is returned.
+ */
+
+dotlock_t
+dotlock_create (const char *file_to_lock, unsigned int flags)
+{
+  static int initialized;
+  dotlock_t h;
+
+  if ( !initialized )
+    {
+      atexit (dotlock_remove_lockfiles);
+      initialized = 1;
+    }
+
+  if ( !file_to_lock )
+    return NULL;  /* Only initialization was requested.  */
+
+  if (flags)
+    {
+      jnlib_set_errno (EINVAL);
+      return NULL;
+    }
+
+  h = jnlib_calloc (1, sizeof *h);
+  if (!h)
+    return NULL;
+  h->extra_fd = -1;
+
+  if (never_lock)
+    {
+      h->disable = 1;
+      LOCK_all_lockfiles ();
+      h->next = all_lockfiles;
+      all_lockfiles = h;
+      UNLOCK_all_lockfiles ();
+      return h;
+    }
+
+#ifdef HAVE_DOSISH_SYSTEM
+  return dotlock_create_w32 (h, file_to_lock);
+#else /*!HAVE_DOSISH_SYSTEM */
+  return dotlock_create_unix (h, file_to_lock);
+#endif /*!HAVE_DOSISH_SYSTEM*/
+}
+
+
+
+/* Convenience function to store a file descriptor (or any any other
+   integer value) in the context of handle H.  */
+void
+dotlock_set_fd (dotlock_t h, int fd)
+{
+  h->extra_fd = fd;
+}
+
+/* Convenience function to retrieve a file descriptor (or any any other
+   integer value) stored in the context of handle H.  */
+int
+dotlock_get_fd (dotlock_t h)
+{
+  return h->extra_fd;
+}
+
+
+
+#ifdef HAVE_POSIX_SYSTEM
+/* Unix specific code of destroy_dotlock.  */
+static void
+dotlock_destroy_unix (dotlock_t h)
+{
+  if (h->locked && h->lockname)
+    unlink (h->lockname);
+  if (h->tname && !h->use_o_excl)
+    unlink (h->tname);
+  jnlib_free (h->tname);
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Windows specific code of destroy_dotlock.  */
+static void
+dotlock_destroy_w32 (dotlock_t h)
+{
+  if (h->locked)
+    {
+      OVERLAPPED ovl;
+
+      memset (&ovl, 0, sizeof ovl);
+      UnlockFileEx (h->lockhd, 0, 1, 0, &ovl);
+    }
+  CloseHandle (h->lockhd);
+}
+#endif /*HAVE_DOSISH_SYSTEM*/
+
+
+/* Destroy the locck handle H and release the lock.  */
+void
+dotlock_destroy (dotlock_t h)
+{
+  dotlock_t hprev, htmp;
+
+  if ( !h )
+    return;
+
+  /* First remove the handle from our global list of all locks. */
+  LOCK_all_lockfiles ();
+  for (hprev=NULL, htmp=all_lockfiles; htmp; hprev=htmp, htmp=htmp->next)
+    if (htmp == h)
+      {
+        if (hprev)
+          hprev->next = htmp->next;
+        else
+          all_lockfiles = htmp->next;
+        h->next = NULL;
+        break;
+      }
+  UNLOCK_all_lockfiles ();
+
+  /* Then destroy the lock. */
+  if (!h->disable)
+    {
+#ifdef HAVE_DOSISH_SYSTEM
+      dotlock_destroy_w32 (h);
+#else /* !HAVE_DOSISH_SYSTEM */
+      dotlock_destroy_unix (h);
+#endif /* HAVE_DOSISH_SYSTEM */
+      jnlib_free (h->lockname);
+    }
+  jnlib_free(h);
+}
+
+
+
+#ifdef HAVE_POSIX_SYSTEM
+/* Unix specific code of make_dotlock.  Returns 0 on success and -1 on
+   error.  */
+static int
+dotlock_take_unix (dotlock_t h, long timeout)
+{
+  int wtime = 0;
+  int sumtime = 0;
+  int pid;
+  int lastpid = -1;
+  int ownerchanged;
+  const char *maybe_dead="";
+  int same_node;
+
+ again:
+  if (h->use_o_excl)
+    {
+      /* No hardlink support - use open(O_EXCL).  */
+      int fd;
+
+      do
+        {
+          jnlib_set_errno (0);
+          fd = open (h->lockname, O_WRONLY|O_CREAT|O_EXCL,
+                     S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR );
+        }
+      while (fd == -1 && errno == EINTR);
+
+      if (fd == -1 && errno == EEXIST)
+        ; /* Lock held by another process.  */
+      else if (fd == -1)
+        {
+          my_error_2 ("lock not made: open(O_EXCL) of '%s' failed: %s\n",
+                      h->lockname, strerror (errno));
+          return -1;
+        }
+      else
+        {
+          char pidstr[16];
+
+          snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid());
+          if (write (fd, pidstr, 11 ) == 11
+              && write (fd, h->tname + h->nodename_off,h->nodename_len)
+              == h->nodename_len
+              && write (fd, "\n", 1) == 1
+              && !close (fd))
+            {
+              h->locked = 1;
+              return 0;
+            }
+          /* Write error.  */
+          my_error_2 ("lock not made: writing to '%s' failed: %s\n",
+                      h->lockname, strerror (errno));
+          close (fd);
+          unlink (h->lockname);
+          return -1;
+        }
+    }
+  else /* Standard method:  Use hardlinks.  */
+    {
+      struct stat sb;
+
+      /* We ignore the return value of link() because it is unreliable.  */
+      (void) link (h->tname, h->lockname);
+
+      if (stat (h->tname, &sb))
+        {
+          my_error_1 ("lock not made: Oops: stat of tmp file failed: %s\n",
+                      strerror (errno));
+          /* In theory this might be a severe error: It is possible
+             that link succeeded but stat failed due to changed
+             permissions.  We can't do anything about it, though.  */
+          return -1;
+        }
+
+      if (sb.st_nlink == 2)
+        {
+          h->locked = 1;
+          return 0; /* Okay.  */
+        }
+    }
+
+  /* Check for stale lock files.  */
+  if ( (pid = read_lockfile (h, &same_node)) == -1 )
+    {
+      if ( errno != ENOENT )
+        {
+          my_info_0 ("cannot read lockfile\n");
+          return -1;
+        }
+      my_info_0 ("lockfile disappeared\n");
+      goto again;
+    }
+  else if ( pid == getpid() && same_node )
+    {
+      my_info_0 ("Oops: lock already held by us\n");
+      h->locked = 1;
+      return 0; /* okay */
+    }
+  else if ( same_node && kill (pid, 0) && errno == ESRCH )
+    {
+      /* Note: It is unlikley that we get a race here unless a pid is
+         reused too fast or a new process with the same pid as the one
+         of the stale file tries to lock right at the same time as we.  */
+      my_info_1 (_("removing stale lockfile (created by %d)\n"), pid);
+      unlink (h->lockname);
+      goto again;
+    }
+
+  if (lastpid == -1)
+    lastpid = pid;
+  ownerchanged = (pid != lastpid);
+
+  if (timeout)
+    {
+      struct timeval tv;
+
+      /* Wait until lock has been released.  We use increasing retry
+         intervals of 50ms, 100ms, 200ms, 400ms, 800ms, 2s, 4s and 8s
+         but reset it if the lock owner meanwhile changed.  */
+      if (!wtime || ownerchanged)
+        wtime = 50;
+      else if (wtime < 800)
+        wtime *= 2;
+      else if (wtime == 800)
+        wtime = 2000;
+      else if (wtime < 8000)
+        wtime *= 2;
+
+      if (timeout > 0)
+        {
+          if (wtime > timeout)
+            wtime = timeout;
+          timeout -= wtime;
+        }
+
+      sumtime += wtime;
+      if (sumtime >= 1500)
+        {
+          sumtime = 0;
+          my_info_3 (_("waiting for lock (held by %d%s) %s...\n"),
+                     pid, maybe_dead, maybe_deadlock(h)? _("(deadlock?) "):"");
+        }
+
+
+      tv.tv_sec = wtime / 1000;
+      tv.tv_usec = (wtime % 1000) * 1000;
+      select (0, NULL, NULL, NULL, &tv);
+      goto again;
+    }
+
+  jnlib_set_errno (EACCES);
+  return -1;
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Windows specific code of make_dotlock.  Returns 0 on success and -1 on
+   error.  */
+static int
+dotlock_take_w32 (dotlock_t h, long timeout)
+{
+  int wtime = 0;
+  int w32err;
+  OVERLAPPED ovl;
+
+ again:
+  /* Lock one byte at offset 0.  The offset is given by OVL.  */
+  memset (&ovl, 0, sizeof ovl);
+  if (LockFileEx (h->lockhd, (LOCKFILE_EXCLUSIVE_LOCK
+                              | LOCKFILE_FAIL_IMMEDIATELY), 0, 1, 0, &ovl))
+    {
+      h->locked = 1;
+      return 0; /* okay */
+    }
+
+  w32err = GetLastError ();
+  if (w32err != ERROR_LOCK_VIOLATION)
+    {
+      my_error_2 (_("lock '%s' not made: %s\n"),
+                  h->lockname, w32_strerror (w32err));
+      return -1;
+    }
+
+  if (timeout)
+    {
+      /* Wait until lock has been released.  We use retry intervals of
+         50ms, 100ms, 200ms, 400ms, 800ms, 2s, 4s and 8s.  */
+      if (!wtime)
+        wtime = 50;
+      else if (wtime < 800)
+        wtime *= 2;
+      else if (wtime == 800)
+        wtime = 2000;
+      else if (wtime < 8000)
+        wtime *= 2;
+
+      if (timeout > 0)
+        {
+          if (wtime > timeout)
+            wtime = timeout;
+          timeout -= wtime;
+        }
+
+      if (wtime >= 800)
+        my_info_1 (_("waiting for lock %s...\n"), h->lockname);
+
+      Sleep (wtime);
+      goto again;
+    }
+
+  return -1;
+}
+#endif /*HAVE_DOSISH_SYSTEM*/
+
+
+/* Take a lock on H.  A value of 0 for TIMEOUT returns immediately if
+   the lock can't be taked, -1 waits forever (hopefully not), other
+   values wait for TIMEOUT milliseconds.  Returns: 0 on success  */
+int
+dotlock_take (dotlock_t h, long timeout)
+{
+  int ret;
+
+  if ( h->disable )
+    return 0; /* Locks are completely disabled.  Return success. */
+
+  if ( h->locked )
+    {
+      my_debug_1 ("Oops, '%s' is already locked\n", h->lockname);
+      return 0;
+    }
+
+#ifdef HAVE_DOSISH_SYSTEM
+  ret = dotlock_take_w32 (h, timeout);
+#else /*!HAVE_DOSISH_SYSTEM*/
+  ret = dotlock_take_unix (h, timeout);
+#endif /*!HAVE_DOSISH_SYSTEM*/
+
+  return ret;
+}
+
+
+
+#ifdef HAVE_POSIX_SYSTEM
+/* Unix specific code of release_dotlock.  */
+static int
+dotlock_release_unix (dotlock_t h)
+{
+  int pid, same_node;
+
+  pid = read_lockfile (h, &same_node);
+  if ( pid == -1 )
+    {
+      my_error_0 ("release_dotlock: lockfile error\n");
+      return -1;
+    }
+  if ( pid != getpid() || !same_node )
+    {
+      my_error_1 ("release_dotlock: not our lock (pid=%d)\n", pid);
+      return -1;
+    }
+
+  if ( unlink( h->lockname ) )
+    {
+      my_error_1 ("release_dotlock: error removing lockfile '%s'\n",
+                  h->lockname);
+      return -1;
+    }
+  /* Fixme: As an extra check we could check whether the link count is
+     now really at 1. */
+  return 0;
+}
+#endif /*HAVE_POSIX_SYSTEM */
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Windows specific code of release_dotlock.  */
+static int
+dotlock_release_w32 (dotlock_t h)
+{
+  OVERLAPPED ovl;
+
+  memset (&ovl, 0, sizeof ovl);
+  if (!UnlockFileEx (h->lockhd, 0, 1, 0, &ovl))
+    {
+      my_error_2 ("release_dotlock: error removing lockfile '%s': %s\n",
+                  h->lockname, w32_strerror (-1));
+      return -1;
+    }
+
+  return 0;
+}
+#endif /*HAVE_DOSISH_SYSTEM */
+
+
+/* Release a lock.  Returns 0 on success.  */
+int
+dotlock_release (dotlock_t h)
+{
+  int ret;
+
+  /* To avoid atexit race conditions we first check whether there are
+     any locks left.  It might happen that another atexit handler
+     tries to release the lock while the atexit handler of this module
+     already ran and thus H is undefined.  */
+  LOCK_all_lockfiles ();
+  ret = !all_lockfiles;
+  UNLOCK_all_lockfiles ();
+  if (ret)
+    return 0;
+
+  if ( h->disable )
+    return 0;
+
+  if ( !h->locked )
+    {
+      my_debug_1 ("Oops, '%s' is not locked\n", h->lockname);
+      return 0;
+    }
+
+#ifdef HAVE_DOSISH_SYSTEM
+  ret = dotlock_release_w32 (h);
+#else
+  ret = dotlock_release_unix (h);
+#endif
+
+  if (!ret)
+    h->locked = 0;
+  return ret;
+}
+
+
+
+/* Remove all lockfiles.  This is called by the atexit handler
+   installed by this module but may also be called by other
+   termination handlers.  */
+void
+dotlock_remove_lockfiles (void)
+{
+  dotlock_t h, h2;
+
+  /* First set the lockfiles list to NULL so that for example
+     dotlock_release is ware that this fucntion is currently
+     running.  */
+  LOCK_all_lockfiles ();
+  h = all_lockfiles;
+  all_lockfiles = NULL;
+  UNLOCK_all_lockfiles ();
+
+  while ( h )
+    {
+      h2 = h->next;
+      dotlock_destroy (h);
+      h = h2;
+    }
+}
diff --git a/dotlock.h b/dotlock.h
new file mode 100644
index 0000000..3fb9bcb
--- /dev/null
+++ b/dotlock.h
@@ -0,0 +1,112 @@
+/* dotlock.h - dotfile locking declarations
+ * Copyright (C) 2000, 2001, 2006, 2011 Free Software Foundation, Inc.
+ *
+ * This file is part of JNLIB, which is a subsystem of GnuPG.
+ *
+ * JNLIB is free software; you can redistribute it and/or modify it
+ * under the terms of either
+ *
+ *   - the GNU Lesser General Public License as published by the Free
+ *     Software Foundation; either version 3 of the License, or (at
+ *     your option) any later version.
+ *
+ * or
+ *
+ *   - the GNU General Public License as published by the Free
+ *     Software Foundation; either version 2 of the License, or (at
+ *     your option) any later version.
+ *
+ * or both in parallel, as here.
+ *
+ * JNLIB 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 copies of the GNU General Public License
+ * and the GNU Lesser General Public License along with this program;
+ * if not, see <http://www.gnu.org/licenses/>.
+ *
+ * ALTERNATIVELY, this file may be distributed under the terms of the
+ * following license, in which case the provisions of this license are
+ * required INSTEAD OF the GNU Lesser General License or the GNU
+ * General Public License. If you wish to allow use of your version of
+ * this file only under the terms of the GNU Lesser General License or
+ * the GNU General Public License, and not to allow others to use your
+ * version of this file under the terms of the following license,
+ * indicate your decision by deleting this paragraph and the license
+ * below.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, and the entire permission notice in its entirety,
+ *    including the disclaimer of warranties.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef LIBJNLIB_DOTLOCK_H
+#define LIBJNLIB_DOTLOCK_H
+
+/* See dotlock.c for a description.  */
+
+#ifdef DOTLOCK_EXT_SYM_PREFIX
+# ifndef _DOTLOCK_PREFIX
+#  define _DOTLOCK_PREFIX1(x,y)  x ## y
+#  define _DOTLOCK_PREFIX2(x,y) _DOTLOCK_PREFIX1(x,y)
+#  define _DOTLOCK_PREFIX(x)    _DOTLOCK_PREFIX2(DOTLOCK_EXT_SYM_PREFIX,x)
+# endif /*_DOTLOCK_PREFIX*/
+# define dotlock_disable          _DOTLOCK_PREFIX(dotlock_disable)
+# define dotlock_create           _DOTLOCK_PREFIX(dotlock_create)
+# define dotlock_set_fd           _DOTLOCK_PREFIX(dotlock_set_fd)
+# define dotlock_get_fd           _DOTLOCK_PREFIX(dotlock_get_fd)
+# define dotlock_destroy          _DOTLOCK_PREFIX(dotlock_destroy)
+# define dotlock_take             _DOTLOCK_PREFIX(dotlock_take)
+# define dotlock_release          _DOTLOCK_PREFIX(dotlock_release)
+# define dotlock_remove_lockfiles _DOTLOCK_PREFIX(dotlock_remove_lockfiles)
+#endif /*DOTLOCK_EXT_SYM_PREFIX*/
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0
+}
+#endif
+#endif
+
+
+struct dotlock_handle;
+typedef struct dotlock_handle *dotlock_t;
+
+void dotlock_disable (void);
+dotlock_t dotlock_create (const char *file_to_lock, unsigned int flags);
+void dotlock_set_fd (dotlock_t h, int fd);
+int  dotlock_get_fd (dotlock_t h);
+void dotlock_destroy (dotlock_t h);
+int dotlock_take (dotlock_t h, long timeout);
+int dotlock_release (dotlock_t h);
+void dotlock_remove_lockfiles (void);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /*LIBJNLIB_DOTLOCK_H*/
diff --git a/kiki.cabal b/kiki.cabal
index 1fd9507..fbf9470 100644
--- a/kiki.cabal
+++ b/kiki.cabal
@@ -22,3 +22,4 @@ Executable kiki
                      unix, time, crypto-api, cryptocipher (>=0.3.7),
                      containers -any
     ghc-options:     -O2
+    c-sources: dotlock.c