1 files changed, 72 insertions, 0 deletions
diff --git a/Chalice/tests/examples/CopyLessMessagePassing.chalice b/Chalice/tests/examples/CopyLessMessagePassing.chalice
new file mode 100644
index 00000000..4b8a9389
--- /dev/null
+++ b/Chalice/tests/examples/CopyLessMessagePassing.chalice
@@ -0,0 +1,72 @@
+// program inspired by "Proving Copyless Message Passing" (Villard, Lozes and Calcagno, APLAS 2009)
+
+// msg tag indicates what the type of the message
+// channel is freed by Getter when it completes
+
+// todo: accept ack message before sending the next one (requires sending negative credit!)
+
+channel C(msg: int, n: Node) where n!= null && acc(n.next) && acc(n.mu) && (msg == 1 ==> credit(this, 1)) && (msg == 0 ==> acc(this.mu, 50));
+
+class Node {
+  var next: Node;
+  
+  function length(): int
+    requires this.list;
+  {
+    unfolding this.list in 1 + (next == null ? 0 : next.length())
+  }
+  
+  predicate list {
+    acc(next) && acc(mu) && (next != null ==> next.list)
+  }
+}
+
+class Program {
+  method Putter(e: C, x0: Node) 
+    requires e!= null && acc(e.mu, 50) && (x0 != null ==> x0.list) && (x0 != null ==> credit(e, - 1));
+  {
+    var x: Node := x0;
+    var t: Node;
+    
+    while(x != null) 
+      invariant (x != null ==> x.list) && (x!=null ==> acc(e.mu, 50)) && (x != null ==> credit(e, - 1));
+    {
+      unfold x.list;
+      t := x.next;
+      if(t != null) {
+        send e(1, x);
+      } else {
+        send e(0, x);
+      }
+      x := t;
+    }
+  }  
+  
+  method Getter(f: C) 
+    requires f!= null && credit(f, 1) && acc(f.mu, 50) && waitlevel << f.mu;
+  {
+    var x: Node := null;
+    var msg := 1;
+    while(msg != 0)
+      invariant acc(f.mu, 50) && waitlevel << f.mu && (msg == 1 ==> credit(f, 1)) && (msg == 0 ==> acc(f.mu, 50));
+    {
+      receive msg, x := f;
+      if(msg == 1) {
+        free x;
+      }
+    }
+    free f; // close the channel
+  } 
+
+  method Main(x: Node)
+    requires x != null;
+    requires x.list;
+  {
+    var e := new C;
+    fork Putter(e, x);
+    fork Getter(e);
+  }  
+}
+
+
+