1 files changed, 76 insertions, 0 deletions
diff --git a/libgo/runtime/go-can-convert-interface.c b/libgo/runtime/go-can-convert-interface.c
new file mode 100644
index 0000000000..83217ab95b
--- /dev/null
+++ b/libgo/runtime/go-can-convert-interface.c
@@ -0,0 +1,76 @@
+/* go-can-convert-interface.c -- can we convert to an interface?
+
+   Copyright 2009 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-assert.h"
+#include "go-type.h"
+#include "interface.h"
+
+/* Return whether we can convert from the type in FROM_DESCRIPTOR to
+   the interface in TO_DESCRIPTOR.  This is used for type
+   switches.  */
+
+_Bool
+__go_can_convert_to_interface (
+    const struct __go_type_descriptor *to_descriptor,
+    const struct __go_type_descriptor *from_descriptor)
+{
+  const struct __go_interface_type *to_interface;
+  int to_method_count;
+  const struct __go_interface_method *to_method;
+  const struct __go_uncommon_type *from_uncommon;
+  int from_method_count;
+  const struct __go_method *from_method;
+  int i;
+
+  /* In a type switch FROM_DESCRIPTOR can be NULL.  */
+  if (from_descriptor == NULL)
+    return 0;
+
+  __go_assert (to_descriptor->__code == GO_INTERFACE);
+  to_interface = (const struct __go_interface_type *) to_descriptor;
+  to_method_count = to_interface->__methods.__count;
+  to_method = ((const struct __go_interface_method *)
+	       to_interface->__methods.__values);
+
+  from_uncommon = from_descriptor->__uncommon;
+  if (from_uncommon == NULL)
+    {
+      from_method_count = 0;
+      from_method = NULL;
+    }
+  else
+    {
+      from_method_count = from_uncommon->__methods.__count;
+      from_method = ((const struct __go_method *)
+		     from_uncommon->__methods.__values);
+    }
+
+  for (i = 0; i < to_method_count; ++i)
+    {
+      while (from_method_count > 0
+	     && (!__go_ptr_strings_equal (from_method->__name,
+					  to_method->__name)
+		 || !__go_ptr_strings_equal (from_method->__pkg_path,
+					     to_method->__pkg_path)))
+	{
+	  ++from_method;
+	  --from_method_count;
+	}
+
+      if (from_method_count == 0)
+	return 0;
+
+      if (!__go_type_descriptors_equal (from_method->__mtype,
+					to_method->__type))
+	return 0;
+
+      ++to_method;
+      ++from_method;
+      --from_method_count;
+    }
+
+  return 1;
+}