1 files changed, 19 insertions, 0 deletions
diff --git a/lockdir.tl b/lockdir.tl
new file mode 100644
index 0000000..3d6fe0f
--- /dev/null
+++ b/lockdir.tl
@@ -0,0 +1,19 @@
+(defun acquire-lock (path)
+  (let ((lock `@path.#lock#`)
+        (start-time (time)))
+    (while (< (- (time) start-time) 30)
+      (catch (if (mkdir lock #o700)
+               (return-from acquire-lock lock))
+        (file-error (e)
+          (unless (= 17 (errno))
+            (throw 'file-error e))
+          (usleep 1000000))))
+    (error "acquire-lock: unable to acquire ~a" lock))) 
+
+(defun release-lock (lock)
+  (ignerr (remove-path lock)))
+
+(defmacro with-lock (path . body)
+  (let ((lock (gensym)))
+    ^(with-resources ((,lock (acquire-lock ,path) (release-lock ,lock)))
+       ,*body)))