- Add functionality to morph a string into an external string

vm/dart_api_impl.cc

Index: vm/dart_api_impl.cc
===================================================================
--- vm/dart_api_impl.cc	(revision 14589)
+++ vm/dart_api_impl.cc	(working copy)
@@ -1707,6 +1707,32 @@
 }
 
 
+DART_EXPORT Dart_Handle Dart_MakeExternalString(Dart_Handle str,
+                                                void* array,
+                                                intptr_t length,
+                                                void* peer,
+                                                Dart_PeerFinalizer cback) {
+  Isolate* isolate = Isolate::Current();
+  DARTSCOPE(isolate);
+  const String& str_obj = Api::UnwrapStringHandle(isolate, str);
+  if (str_obj.IsNull() || str_obj.IsExternal()) {
+    RETURN_TYPE_ERROR(isolate, str, String);

[Tom Ball, 2012/11/07 00:38:43]

Is passing in an external string necessarily an error?  The original handle
could instead be returned.

[siva, 2012/11/07 21:43:27]

Yes we could.

Does that make sense however, it seems like a lot of code
to return back the same handle. I am wondering if the
embedder code would prefer knowing when this happens.

On 2012/11/07 00:38:43, Tom Ball wrote:

+  }
+  if (array == NULL) {
+    RETURN_NULL_ERROR(array);
+  }
+  intptr_t str_length = (str_obj.Length() * str_obj.CharSize());
+  if ((length < str_length) || (length > String::kMaxElements)) {
+    return Api::NewError("Dart_MakeExternalString "
+                         "expects argument length to be in the range"
+                         "[%"Pd"..%"Pd"].",
+                         str_length, String::kMaxElements);
+  }
+  return Api::NewHandle(isolate,
+                        str_obj.MakeExternal(array, length, peer, cback));
+}
+
+
 // --- Lists ---