Add an external array type to support typed arrays.

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 5872b4cd6434c0b067c82480167bfa28c1da7cfd..8fe419a42fb8855b2718ca6b0049294252047889 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -52,6 +52,7 @@ namespace dart {
     V(Bool)                                                                    \
     V(Array)                                                                   \
       V(ImmutableArray)                                                        \
+    V(ExternalArray)                                                           \
     V(Closure)                                                                 \
     V(Stacktrace)                                                              \
     V(JSRegExp)                                                                \
@@ -719,6 +720,14 @@ class RawImmutableArray : public RawArray {
 };
 
 
+class RawExternalArray : public RawInstance {
+  RAW_HEAP_OBJECT_IMPLEMENTATION(ExternalArray);
+
+  RawSmi* length_;

[siva, 2011/11/02 17:05:31]

Do we want this to be RawSmi or intptr_t i.e have a restriction on how big the
external array can be or let it be larger than what Smi can hold?

Also missing from() and to() methods, even though you might have only a RawSmi
in here it is probably a good idea to add the from and to so that it is
consistent with the others and if somebody decides to add a field in here later
it is not overlooked. 

[cshapiro, 2011/11/04 18:16:21]

I am partial to having the length parameter to be a Smi as the type should
implement List and Collection and the extant implementations of these types are
limit to Smi indices.  I am not sure how to reconcile this disparity in reach. 
What do you think?

As for the from and to methods, I will go ahead add that.

+  uint8_t* data_;
+};
+
+
 class RawClosure : public RawInstance {
   RAW_HEAP_OBJECT_IMPLEMENTATION(Closure);