From 2a4f421a74b6e31e7718d206be704f1d42a268a2 Mon Sep 17 00:00:00 2001
From: Javier Sancho <jsf@jsancho.org>
Date: Sun, 3 Nov 2013 15:42:25 +0100
Subject: [PATCH] Improving with-engine

* src/engine.scm: with-engine now saves current engine for recursive
                  calls and uses engine mutex for exclusive access
---
 src/engine.scm | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/engine.scm b/src/engine.scm
index 6d5e0e7..0770e09 100644
--- a/src/engine.scm
+++ b/src/engine.scm
@@ -94,10 +94,12 @@
 (define-syntax with-engine
   (syntax-rules ()
     ((_ engine body ...)
-     (begin
+     (let ((old-engine (current-engine)))
        (set-current-engine! engine)
-       (let ((res (begin body ...)))
-	 (set-current-engine! #f)
+       (let ((res (with-mutex (engine-mutex engine)
+		    body
+		    ...)))
+	 (set-current-engine! old-engine)
 	 res)))))
 
 (export current-engine
-- 
2.39.5