Add Dart_IdentityHash to the embedding API.

Add Dart_IdentityHash to the embedding API.

(For use in ScriptObjectTraits.)

R=asiva@google.com

Committed: https://code.google.com/p/dart/source/detail?r=35750

[siva, 2014-05-02 17:29:58]

https://codereview.chromium.org/263823004/diff/20001/runtime/include/dart_api.h
File runtime/include/dart_api.h (right):

https://codereview.chromium.org/263823004/diff/20001/runtime/include/dart_api...
runtime/include/dart_api.h:396: * codes of non-equal objects are not necessarily
distinct.
The comment should also document the input param and the return values

(see comment above for Dart_IdentityEquals)

Maybe the signature should be

DART_EXPORT Dart_Handle Dart_IdentityHash(Dart_Handle obj, uint64_t* value);

That way you can return error in case of input problems.

https://codereview.chromium.org/263823004/diff/20001/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

https://codereview.chromium.org/263823004/diff/20001/runtime/vm/dart_api_impl...
runtime/vm/dart_api_impl.cc:609: }
Maybe use the pattern:
  const Instance& obj = Api::UnwrapInstanceHandle(isolate, exception);
  if (obj.IsNull()) {
    RETURN_TYPE_ERROR(isolate, exception, Instance);
  }

https://codereview.chromium.org/263823004/diff/20001/runtime/vm/dart_api_impl...
runtime/vm/dart_api_impl.cc:641: }
We have a similar pattern in Dart_NativeIntegerArgument maybe you could factor
this part out into a static function.

[rmacnak, 2014-05-02 21:19:13]

https://codereview.chromium.org/263823004/diff/20001/runtime/include/dart_api.h
File runtime/include/dart_api.h (right):

https://codereview.chromium.org/263823004/diff/20001/runtime/include/dart_api...
runtime/include/dart_api.h:396: * codes of non-equal objects are not necessarily
distinct.
On 2014/05/02 17:29:59, siva wrote:
> The comment should also document the input param and the return values
> 
> (see comment above for Dart_IdentityEquals)

Done.

> Maybe the signature should be
> 
> DART_EXPORT Dart_Handle Dart_IdentityHash(Dart_Handle obj, uint64_t* value);
> 
> That way you can return error in case of input problems.

There is no error case. Dart_IdentityEquals accepts any handle so
Dart_IdentityHash must as well. We merely give low-quality hashes for
non-instances.

https://codereview.chromium.org/263823004/diff/20001/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

https://codereview.chromium.org/263823004/diff/20001/runtime/vm/dart_api_impl...
runtime/vm/dart_api_impl.cc:641: }
On 2014/05/02 17:29:59, siva wrote:
> We have a similar pattern in Dart_NativeIntegerArgument maybe you could factor
> this part out into a static function.

Given the lack of failure cases here I don't think there's a good refactoring.
But Dart_NativeIntegerArgument and Dart_IntegerToInt64 could share some code if
we're okay with slightly less specific error messages.

[siva, 2014-05-02 21:50:51]

lgtm

[rmacnak, 2014-05-05 17:32:25]

Committed patchset #3 manually as r35750 (presubmit successful).