1 files changed, 49 insertions, 0 deletions
diff --git a/libgo/runtime/go-assert-interface.c b/libgo/runtime/go-assert-interface.c
new file mode 100644
index 0000000000..57a092d59b
--- /dev/null
+++ b/libgo/runtime/go-assert-interface.c
@@ -0,0 +1,49 @@
+/* go-assert-interface.c -- interface type assertion for Go.
+
+   Copyright 2010 The Go Authors. All rights reserved.
+   Use of this source code is governed by a BSD-style
+   license that can be found in the LICENSE file.  */
+
+#include "go-alloc.h"
+#include "go-assert.h"
+#include "go-panic.h"
+#include "interface.h"
+
+/* This is called by the compiler to implement a type assertion from
+   one interface type to another.  This returns the value that should
+   go in the first field of the result tuple.  The result may be an
+   empty or a non-empty interface.  */
+
+const void *
+__go_assert_interface (const struct __go_type_descriptor *lhs_descriptor,
+		       const struct __go_type_descriptor *rhs_descriptor)
+{
+  const struct __go_interface_type *lhs_interface;
+
+  if (rhs_descriptor == NULL)
+    {
+      struct __go_empty_interface panic_arg;
+
+      /* A type assertion is not permitted with a nil interface.  */
+
+      newTypeAssertionError (NULL,
+			     NULL,
+			     lhs_descriptor,
+			     NULL,
+			     NULL,
+			     lhs_descriptor->__reflection,
+			     NULL,
+			     &panic_arg);
+      __go_panic (panic_arg);
+    }
+
+  /* A type assertion to an empty interface just returns the object
+     descriptor.  */
+
+  __go_assert (lhs_descriptor->__code == GO_INTERFACE);
+  lhs_interface = (const struct __go_interface_type *) lhs_descriptor;
+  if (lhs_interface->__methods.__count == 0)
+    return rhs_descriptor;
+
+  return __go_convert_interface_2 (lhs_descriptor, rhs_descriptor, 0);
+}