diff --git a/aos/ipc_lib/index.cc b/aos/ipc_lib/index.cc
new file mode 100644
index 0000000..ed58806
--- /dev/null
+++ b/aos/ipc_lib/index.cc
@@ -0,0 +1,33 @@
+#include "aos/ipc_lib/index.h"
+
+#include <string>
+#include <sstream>
+
+namespace aos {
+namespace ipc_lib {
+
+::std::string QueueIndex::DebugString() const {
+  if (valid()) {
+    ::std::stringstream s;
+    s << "QueueIndex(" << index_ << "/0x" << ::std::hex << index_ << ::std::dec
+      << ", count=" << count_ << ")";
+    return s.str();
+  } else {
+    return "QueueIndex::Invalid()";
+  }
+}
+
+::std::string Index::DebugString() const {
+  if (valid()) {
+    ::std::stringstream s;
+    s << "Index(queue_index=" << queue_index() << "/0x" << ::std::hex
+      << queue_index() << ::std::dec << ", message_index=" << message_index()
+      << ")";
+    return s.str();
+  } else {
+    return "QueueIndex::Invalid()";
+  }
+}
+
+}  // namespace ipc_lib
+}  // namespace aos