In process locking implemented, not sqlite locking.

keystore.rkt

@@ -27,8 +27,10 @@
          ks-abort-transaction
          )
 
+(define (any? a) #t)
+
 (define-struct keystore
-  (file path dbh)
+  (file path dbh lock-sem (in-lock #:mutable) (entered #:mutable))
   #:transparent
   )
 
@@ -46,7 +48,7 @@
     (let ((dbh (sqlite3-connect #:database path #:mode 'create)))
       (query-exec dbh "CREATE TABLE IF NOT EXISTS keystore(key varchar primary key, value varchar, str_key varchar);")
       (query-exec dbh "CREATE INDEX IF NOT EXISTS keystore_idx on keystore(str_key);")
-      (make-keystore file path dbh))))
+      (make-keystore file path dbh (make-semaphore 1) #f 0))))
 
 (define/contract (ks-close ksh)
   (-> keystore? boolean?)
@@ -54,6 +56,27 @@
     (disconnect dbh)
     #t))
 
+(define/contract (ks-with-lock ksh proc)
+  (-> keystore? procedure? any?)
+  (dynamic-wind
+   (λ ()
+     (cond
+       ((eq? (keystore-in-lock ksh) (current-thread))
+        (set-keystore-entered! ksh (+ keystore-entered ksh) 1))
+       (else 
+        (semaphore-wait (keystore-lock-sem ksh))
+        (set-keystore-entered! ksh 1)
+        ))
+     (set-keystore-in-lock! ksh (current-thread)))
+   proc
+   (λ ()
+     (set-keystore-entered! (- (keystore-entered ksh) 1))
+     (when (= (keystore-entered ksh) 0)
+       (set-keystore-in-lock! ksh #f)
+       (semaphore-post (keystore-lock-sem ksh))))
+   )
+  )
+
 (define/contract (ks-set! ksh key value)
   (-> keystore? any/c any/c boolean?)
    (ks-set!* (keystore-dbh ksh) (key->string key) (format "~a" key) (value->string value)))