Improve performance of reading a protobuf buffer

Improve performance of reading a protobuf buffer

* Avoid the use of two vars for handling the read limit
* Avoid always copying the buffer
* Improve reading of varint which was high on the profile

R=sigmund@google.com
BUG=

Committed: https://github.com/dart-lang/protobuf/commit/1b22ec4bd717e16e1c5dc0b1e3051ab33c3f7bf1

[Anders Johnsen, 2014-12-19 08:32:25]

ajohnsen@google.com changed reviewers:
+ ajohnsen@google.com

[Anders Johnsen, 2014-12-19 08:32:25]

DBC

https://chromiumcodereview.appspot.com/798683007/diff/1/lib/src/protobuf/code...
File lib/src/protobuf/coded_buffer_reader.dart (right):

https://chromiumcodereview.appspot.com/798683007/diff/1/lib/src/protobuf/code...
lib/src/protobuf/coded_buffer_reader.dart:23: _buffer = buffer,// is Uint8List ?
buffer : new Uint8List(buffer.length)..setRange(0, buffer.length, buffer),
Out-commented code

[Søren Gjesse, 2014-12-19 09:05:28]

https://chromiumcodereview.appspot.com/798683007/diff/1/lib/src/protobuf/code...
File lib/src/protobuf/coded_buffer_reader.dart (right):

https://chromiumcodereview.appspot.com/798683007/diff/1/lib/src/protobuf/code...
lib/src/protobuf/coded_buffer_reader.dart:23: _buffer = buffer,// is Uint8List ?
buffer : new Uint8List(buffer.length)..setRange(0, buffer.length, buffer),
On 2014/12/19 08:32:25, Anders Johnsen wrote:
> Out-commented code

Oops - testing code. Fixed.

[Siggi Cherem (dart-lang), 2014-12-19 17:42:56]

lgtm

[sra1, 2014-12-19 17:53:46]

sra@google.com changed reviewers:
+ sra@google.com

[sra1, 2014-12-19 17:53:47]

How much was the performance improvement on dart2js?

[Søren Gjesse, 2015-01-05 13:51:01]

On 2014/12/19 17:53:47, sra1 wrote:
> How much was the performance improvement on dart2js?

I just tried to measure, and could not see any difference in the numbers when
running the generated JavaScript. Btw. generated JavaScript is ~10x SLOWER than
the VM (in a simple protobuf benchmark).

[Søren Gjesse, 2015-01-05 13:52:53]

Committed patchset #2 (id:20001) manually as
1b22ec4bd717e16e1c5dc0b1e3051ab33c3f7bf1 (presubmit successful).