1 files changed, 56 insertions, 0 deletions
diff --git a/lib/erl_interface/src/misc/ei_trace.c b/lib/erl_interface/src/misc/ei_trace.c
new file mode 100644
index 0000000000..fb183c8be4
--- /dev/null
+++ b/lib/erl_interface/src/misc/ei_trace.c
@@ -0,0 +1,56 @@
+/*
+ * %CopyrightBegin%
+ * 
+ * Copyright Ericsson AB 1998-2009. All Rights Reserved.
+ * 
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ * 
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ * 
+ * %CopyrightEnd%
+ *
+
+ */
+#include "eidef.h"
+#include "ei_trace.h"
+
+/* this is our lamport clock */
+erlang_trace *ei_trace(int query, erlang_trace *token)
+{
+  /* FIXME problem for threaded ? */ 
+  static erlang_trace save_token;
+  static int tracing = 0;
+  static int clock = 0;
+
+  
+  switch (query) {
+  case -1: /* we are no longer tracing */
+    tracing = 0;
+    break;
+    
+  case 0: /* are we tracing? */
+    if (tracing) {
+      clock++;
+      save_token.prev = save_token.serial++;
+      return &save_token;
+    }
+    break;
+    
+  case 1: /* we are now tracing */
+    tracing = 1;
+    save_token = *token;
+    if (save_token.serial > clock) 
+      save_token.prev = clock = token->serial;
+    break;
+  }
+
+  return NULL;
+}
+