Mojo C++ bindings: inline pointer encoding/decoding/validating functions.

mojo/public/cpp/bindings/lib/validation_util.h

Index: mojo/public/cpp/bindings/lib/validation_util.h
diff --git a/mojo/public/cpp/bindings/lib/validation_util.h b/mojo/public/cpp/bindings/lib/validation_util.h
index c883392ebc13fae00fd7e629644a5bca880556ae..1c6c53cb23eba61f6139a66e712ba6055d5628b9 100644
--- a/mojo/public/cpp/bindings/lib/validation_util.h
+++ b/mojo/public/cpp/bindings/lib/validation_util.h
@@ -19,7 +19,15 @@ namespace internal {
 
 // Checks whether decoding the pointer will overflow and produce a pointer
 // smaller than |offset|.
-bool ValidateEncodedPointer(const uint64_t* offset);
+inline bool ValidateEncodedPointer(const uint64_t* offset) {
+  // - Make sure |*offset| is no more than 32-bits.
+  // - Cast |offset| to uintptr_t so overflow behavior is well defined across
+  //   32-bit and 64-bit systems.
+  return *offset <= std::numeric_limits<uint32_t>::max() &&
+         (reinterpret_cast<uintptr_t>(offset) +
+              static_cast<uint32_t>(*offset) >=
+          reinterpret_cast<uintptr_t>(offset));
+}
 
 template <typename T>
 bool ValidatePointer(const Pointer<T>& input,