Narrow when storing to a byte array and implement uint64 get and set.

Narrow when storing to a byte array and implement uint64 get and set.

Previously, the byte array get and set routines for integers would not
correctly narrow an integer when the width of a value being stored was
greater than the element width.  This change implements the behavior in
the Web IDL specification.

In addition, an implementation for uint64 get and set is now provided.

BUG=2042
Committed: https://code.google.com/p/dart/source/detail?r=5738

[cshapiro, 2012-03-21 05:52:17]

Should I add a TODO regarding the shift-and-subtract operations?  I cannot do
the more sensible thing until the snapshot reader works.

[siva, 2012-03-22 00:27:20]

Sure please add the TODO so that we remember to change to the new form once the
bugs are fixed.

http://codereview.chromium.org/9769013/diff/1/runtime/lib/byte_array.cc
File runtime/lib/byte_array.cc (right):

http://codereview.chromium.org/9769013/diff/1/runtime/lib/byte_array.cc#newco...
runtime/lib/byte_array.cc:93: result ^= BigintOperations::NewFromUint64(value); 
                 \
Can these assignments just be = as Integer is a base class of Smi, Mint and
Bigint

[cshapiro, 2012-03-22 00:47:46]

PTAL

I've added comments after each use of the shift-and-subtract.  It is ugly but
that is probably what we want in this case.

http://codereview.chromium.org/9769013/diff/1/runtime/lib/byte_array.cc
File runtime/lib/byte_array.cc (right):

http://codereview.chromium.org/9769013/diff/1/runtime/lib/byte_array.cc#newco...
runtime/lib/byte_array.cc:93: result ^= BigintOperations::NewFromUint64(value); 
                 \
Yes!  Done.

[siva, 2012-03-22 01:07:59]

lgtm

[siva, 2012-03-22 01:08:05]

lgtm