C types and utilities to validate and access struct and message headers

mojo/public/c/bindings/lib/struct.c

Index: mojo/public/c/bindings/lib/struct.c
diff --git a/mojo/public/c/bindings/lib/struct.c b/mojo/public/c/bindings/lib/struct.c
new file mode 100644
index 0000000000000000000000000000000000000000..df791c177ae0aeda72bc27fff3e58898adb18e79
--- /dev/null
+++ b/mojo/public/c/bindings/lib/struct.c
@@ -0,0 +1,25 @@
+// Copyright 2016 The Chromium 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 "mojo/public/c/bindings/struct.h"
+
+#include <stdint.h>
+
+_Static_assert(sizeof(mojo_struct_header_t) == 8u,
+               "mojo_struct_header_t should be 8 bytes");
+
+bool mojo_validate_struct_header(const void* data, size_t size) {
+  if (size < sizeof(mojo_struct_header_t) || size > UINT32_MAX) {
+    return false;
+  }
+
+  const mojo_struct_header_t* header = (const mojo_struct_header_t*)data;
+
+  if (header->num_bytes < sizeof(mojo_struct_header_t) ||
+      header->num_bytes > size) {
+    return false;
+  }
+
+  return true;
+}