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diff --git a/libical/src/libical/filelock.h b/libical/src/libical/filelock.h
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+/*
+  I Stole this from:
+  http://www.cis.temple.edu/~ingargio/old/cis307s96/readings/rwlockexample.html
+
+  CIS 307: An example using Read/Write File Locks
+  [fcntl.h], [fcntl.c], [fcntlmain.c]
+
+In Stevens "Advanced Programming in the Unix Environment" we see ways to use
+the Unix service fcntl to lock portions of a file for reading and writing in
+the manner stated in the Reader and Writer problem [any number of readers at
+a time, but writers must operate alone]. Here we have three files that adapt
+and use the code from Stevens:
+
+*fcntl.h: Specification of the locking functions.
+*fcntl.c: Implementation of the locking functions.
+*fcntlmain.c: Driver that does a simple test of the locking functions.
+
+WARNING: A file lock request which is blocked can be interrupted by a
+signal. In this case the lock operation returns EINTR. Thus we may think we
+got a lock when we really don't. A solution is to block signals when
+locking. Another solution is to test the value returned by the lock
+operation and relock if the value is EINTR. Another solution, which we adopt
+here, is to do nothing about it.
+
+fcntl.h
+
+*/
+
+/* fcntl.h  -- Defines mutexes in terms of read/write locks on files.
+ *             filerwlock, filerwlockCreate, filerwlockDelete,
+ *             filerwreadlock, filerwlockUnlock
+ */
+
+typedef struct {
+    int fd;
+    int n;
+} filerwlock;
+
+/* Create N read/write locks and returns the id of this cluster of locks. */
+filerwlock * filerwlockCreate(char *filename, int n);
+
+/* Delete the cluster of read/write locks associated with fl. */
+int filerwlockDelete(filerwlock *fl);
+
+/* Given the read/write lock cluster fl, lock its ith element */
+int filerwreadlock(filerwlock *fl, int i);
+
+int filerwwritelock(filerwlock *fl, int i);
+
+/* Given the lock cluster fl, unlock its ith element */
+int filerwunlock(filerwlock *fl, int i);
+
+/* Given the lock cluster fl, it read locks all its elements */
+int filerwlongreadlock(filerwlock *fl);
+
+/* Given the lock cluster fl, it unlocks all its elements */
+int filerwlongunlock(filerwlock *fl);