Add support for big integers to the native message format

Add support for big integers to the native message format

Also fixed snapshotting of negative big integers.

R=asiva@google.com

BUG=
TEST=

Committed: https://code.google.com/p/dart/source/detail?r=4078

[siva, 2012-02-09 01:47:27]

LGTM once the openssl references in this code is removed and limited to the
BigIntOperations interface.

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/dart_api_mes...
File runtime/vm/dart_api_message.cc (right):

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/dart_api_mes...
runtime/vm/dart_api_message.cc:199: char* hex_string =
reinterpret_cast<char*>(AllocateTemp(len + 1));
Why do you use this special temp Allocator and not the regular allocator
registered with this reader object?

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/dart_api_mes...
runtime/vm/dart_api_message.cc:209: char* dec_string = BN_bn2dec(bn);
What is the advantage of converting this into a decimal string and not leaving
it as hex string?

Also ditto comment made elsewhere about exposing the OPENSSL stuff here and not
sticking to the BigIntOperations abstraction.

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/raw_object_s...
File runtime/vm/raw_object_snapshot.cc (right):

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/raw_object_s...
runtime/vm/raw_object_snapshot.cc:1188: if (neg) writer->Write<uint8_t>('-');
Could you restruct as follows to make it more clear:
if (neg) {
  writer->WriteIntptrValue(len - 1);  // Include '-' in length.
  writer->Write<uint8_t>('-');
} else {
  writer->WriteIntptrValue(len - 2);
}

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/snapshot.cc
File runtime/vm/snapshot.cc (right):

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/snapshot.cc#...
runtime/vm/snapshot.cc:551: char* hex_string = BN_bn2hex(bn);
Somebody came up with the BigintOperations class in the hope of hiding the fact
that we are using OPENSSL to do the bigint operations and be able to plug in
some other implementation without changing much of the rest of the code.

This assumption is being violated here.

[Søren Gjesse, 2012-02-09 14:08:32]

Thank you for the review

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/dart_api_mes...
File runtime/vm/dart_api_message.cc (right):

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/dart_api_mes...
runtime/vm/dart_api_message.cc:199: char* hex_string =
reinterpret_cast<char*>(AllocateTemp(len + 1));
On 2012/02/09 01:47:27, asiva wrote:
> Why do you use this special temp Allocator and not the regular allocator
> registered with this reader object?

The idea was that temporary data should be freed before returning, but maybe
thats a bad idea.

As suggested we keep the hex string, so temporary allocation for conversion is
not required any more.

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/dart_api_mes...
runtime/vm/dart_api_message.cc:209: char* dec_string = BN_bn2dec(bn);
On 2012/02/09 01:47:27, asiva wrote:
> What is the advantage of converting this into a decimal string and not leaving
> it as hex string?
> 
> Also ditto comment made elsewhere about exposing the OPENSSL stuff here and
not
> sticking to the BigIntOperations abstraction.

Keeping the hex string - no need for bigint operations here any more.

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/raw_object_s...
File runtime/vm/raw_object_snapshot.cc (right):

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/raw_object_s...
runtime/vm/raw_object_snapshot.cc:1188: if (neg) writer->Write<uint8_t>('-');
On 2012/02/09 01:47:27, asiva wrote:
> Could you restruct as follows to make it more clear:
> if (neg) {
>   writer->WriteIntptrValue(len - 1);  // Include '-' in length.
>   writer->Write<uint8_t>('-');
> } else {
>   writer->WriteIntptrValue(len - 2);
> }

Done.

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/snapshot.cc
File runtime/vm/snapshot.cc (right):

https://chromiumcodereview.appspot.com/9363023/diff/1/runtime/vm/snapshot.cc#...
runtime/vm/snapshot.cc:551: char* hex_string = BN_bn2hex(bn);
On 2012/02/09 01:47:27, asiva wrote:
> Somebody came up with the BigintOperations class in the hope of hiding the
fact
> that we are using OPENSSL to do the bigint operations and be able to plug in
> some other implementation without changing much of the rest of the code.
> 
> This assumption is being violated here.

After changing to using the hex format for the data in the Dart_CObject
structure no bignum operations are needed any more.