More RPC protocol WIP.

c++/src/capnp/capability.h

@@ -91,11 +91,11 @@ class Response: public Results::Reader {
   // is move-only -- once it goes out-of-scope, the underlying message will be freed.
 
 public:
-  inline Response(typename Results::Reader reader, kj::Own<ResponseHook>&& hook)
+  inline Response(typename Results::Reader reader, kj::Own<const ResponseHook>&& hook)
       : Results::Reader(reader), hook(kj::mv(hook)) {}
 
 private:
-  kj::Own<ResponseHook> hook;
+  kj::Own<const ResponseHook> hook;
 
   template <typename, typename>
   friend class Request;
@@ -347,6 +347,7 @@ public:
 };
 
 kj::Own<const ClientHook> newBrokenCap(const char* reason);
+kj::Own<const ClientHook> newBrokenCap(kj::Exception&& reason);
 // Helper function that creates a capability which simply throws exceptions when called.
 
 // =======================================================================================

c++/src/capnp/layout.h

@@ -494,6 +494,8 @@ public:
       : segment(nullptr), data(nullptr), pointers(nullptr), dataSize(0),
         pointerCount(0), bit0Offset(0), nestingLimit(0x7fffffff) {}
 
+  const void* getLocation() const { return data; }
+
   inline BitCount getDataSectionSize() const { return dataSize; }
   inline WirePointerCount getPointerSectionSize() const { return pointerCount; }
   inline Data::Reader getDataSectionAsBlob();

c++/src/kj/array.h

@@ -156,6 +156,9 @@ public:
   inline ArrayPtr<T> asPtr() {
     return ArrayPtr<T>(ptr, size_);
   }
+  inline ArrayPtr<const T> asPtr() const {
+    return ArrayPtr<T>(ptr, size_);
+  }
 
   inline size_t size() const { return size_; }
   inline T& operator[](size_t index) const {