Add fast paths for Smi values in the dart embedding api.

vm/dart_api_impl.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_DART_API_IMPL_H_
 #define VM_DART_API_IMPL_H_
 
 #include "vm/allocation.h"
 #include "vm/object.h"
 
@@ skipping 93 matching lines @@
   static FinalizablePersistentHandle* UnwrapAsPrologueWeakPersistentHandle(
       const ApiState& state,
       Dart_Handle object);
 
   // Casts the internal Isolate* type to the external Dart_Isolate type.
   static Dart_Isolate CastIsolate(Isolate* isolate);
 
   // Gets the handle used to designate successful return.
   static Dart_Handle Success(Isolate* isolate);
 
+  // Returns true if the handle holds a Smi.
+  static bool IsSmi(Dart_Handle handle) {

[cshapiro, 2012/04/11 23:29:09]

Why not call the existing predicate after casing the value to a RawObject?

[turnidge, 2012/04/16 20:07:24]

Done.

+    uword value = *(reinterpret_cast<uword*>(handle));
+    return (value & kSmiTagMask) == kSmiTag;
+  }
+
+  // Returns the value of a Smi.
+  static intptr_t SmiValue(Dart_Handle handle) {
+    intptr_t value = *(reinterpret_cast<intptr_t*>(handle));

[cshapiro, 2012/04/11 23:29:09]

This may be another opportunity to reuse existing infrastructure.

[turnidge, 2012/04/16 20:07:24]

Done.  Had to add friend permission though...

+    ASSERT((value & kSmiTagMask) == kSmiTag);
+    return (value >> kSmiTagShift);
+  }
+
   // Generates a handle used to designate an error return.
   static Dart_Handle NewError(const char* format, ...);
 
   // Gets a handle to Null.
   static Dart_Handle Null(Isolate* isolate);
 
   // Gets a handle to True.
   static Dart_Handle True(Isolate* isolate);
 
   // Gets a handle to False
@@ skipping 29 matching lines @@
   }
  private:
   Isolate* saved_isolate_;
 
   DISALLOW_COPY_AND_ASSIGN(IsolateSaver);
 };
 
 }  // namespace dart.
 
 #endif  // VM_DART_API_IMPL_H_