From f61b5371c492b0685c179090372f35329e8a2028 Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Thu, 29 Sep 2011 16:51:48 +0200
Subject: [PATCH] Add dotlock_get_fd and dotlock_set_fd.

---
 common/ChangeLog |  1 +
 common/dotlock.c | 36 ++++++++++++++++++++++++++++++++++--
 common/dotlock.h |  2 ++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/common/ChangeLog b/common/ChangeLog
index 7ed2673ba..1c067cdf5 100644
--- a/common/ChangeLog
+++ b/common/ChangeLog
@@ -4,6 +4,7 @@
 	[DOTLOCK_USE_PTHREAD] (all_lockfiles_mutex): New.
 	(LOCK_all_lockfiles, UNLOCK_all_lockfiles): New.  Use them to
 	protect access to all_lockfiles.
+	(dotlock_set_fd, dotlock_get_fd): New.
 
 2011-09-28  Werner Koch  <wk@g10code.com>
 
diff --git a/common/dotlock.c b/common/dotlock.c
index 146394412..c65f6f637 100644
--- a/common/dotlock.c
+++ b/common/dotlock.c
@@ -100,8 +100,10 @@
      if (dotlock_release (h))
        error ("error releasing lock: %s\n", strerror (errno));
 
-   or, if the lock file is not anymore needed, you may call
-   dotlock_destroy.
+   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
 
@@ -114,6 +116,15 @@
 
    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:
    =============
@@ -336,6 +347,8 @@ struct dotlock_handle
   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 */
@@ -769,6 +782,7 @@ dotlock_create (const char *file_to_lock, unsigned int flags)
   h = jnlib_calloc (1, sizeof *h);
   if (!h)
     return NULL;
+  h->extra_fd = -1;
 
   if (never_lock)
     {
@@ -788,6 +802,24 @@ dotlock_create (const char *file_to_lock, unsigned int flags)
 }
 
 
+
+/* 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.  */
diff --git a/common/dotlock.h b/common/dotlock.h
index 666d0b72c..6ae7836c5 100644
--- a/common/dotlock.h
+++ b/common/dotlock.h
@@ -27,6 +27,8 @@ 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);