Use a list of Uint8List-views instead of a BytesBuilder, to build up websocket messages.

Use a list of Uint8List-views instead of a BytesBuilder, to build up websocket messages.

This avoids a lot of copyings, and in the case of only one payload,
there are no copies at all.

BUG=
R=kasperl@google.com

Committed: https://code.google.com/p/dart/source/detail?r=32122

[kasperl, 2014-01-29 11:10:44]

LGTM.

https://codereview.chromium.org/130913010/diff/1/sdk/lib/io/websocket_impl.dart
File sdk/lib/io/websocket_impl.dart (right):

https://codereview.chromium.org/130913010/diff/1/sdk/lib/io/websocket_impl.da...
sdk/lib/io/websocket_impl.dart:94: if (_payloads.length == 0) return new
Uint8List(0);
Do you have to create a new one here? Cache an empty list for this case if it's
important?

[Anders Johnsen, 2014-01-29 14:23:40]

https://codereview.chromium.org/130913010/diff/1/sdk/lib/io/websocket_impl.dart
File sdk/lib/io/websocket_impl.dart (right):

https://codereview.chromium.org/130913010/diff/1/sdk/lib/io/websocket_impl.da...
sdk/lib/io/websocket_impl.dart:94: if (_payloads.length == 0) return new
Uint8List(0);
On 2014/01/29 11:10:44, kasperl wrote:
> Do you have to create a new one here? Cache an empty list for this case if
it's
> important?

The empty-list case is very rare, and not something we particular want to
optimize for.

[Anders Johnsen, 2014-01-29 14:23:51]

Committed patchset #1 manually as r32122 (presubmit successful).