fasta: Use more efficient Uint16List/Uint32List for line offset information, use hints for length

fasta: Use more efficient Uint16List/Uint32List for line offset information, use hints for length

R=ahe@google.com

Committed: https://github.com/dart-lang/sdk/commit/a94bd171687d5a56aa84e6cf27ada540dad2bed5

[kustermann, 2017-02-22 13:26:45]

Patchset #2 (id:20001) has been deleted

[kustermann, 2017-02-22 13:27:06]

kustermann@google.com changed reviewers:
+ ahe@google.com, vegorov@google.com

[ahe, 2017-02-22 14:36:24]

Thanks for identifying this issue. We could land your CL as is, but I have some
additional considerations I'd like to go over with you in person (tomorrow).

So I don't forget:

* Everything is scanned twice in fasta, second time we shouldn't record line
starts.

* Can we avoid creating a List subclass by having a shared line number buffer?

[kustermann, 2017-02-22 14:53:21]

Let's talk more offline.


> Everything is scanned twice in fasta, second time we shouldn't record line
starts.

Correct, but that seems like an orthogonal CL.


> * Can we avoid creating a List subclass by having a shared line number buffer?

We can avoid creating a List subclass, by just changing all the code that
expects List<int> and replace it to use LineStarts.


Whether it's a good idea to share one buffer for all files is another question.
The current code allows these "hints" which means we never need to grow any of
the arrays, it uses almost always perfect with (16/32 typed_data list) and
length (number of lines).

[ahe, 2017-02-23 12:47:35]

lgtm

https://codereview.chromium.org/2709983002/diff/40001/pkg/front_end/lib/src/f...
File pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart (right):

https://codereview.chromium.org/2709983002/diff/40001/pkg/front_end/lib/src/f...
pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart:1190: // characters.
I don't understand this comment. It seems like you do use the hint.

[kustermann, 2017-02-24 14:24:49]

https://codereview.chromium.org/2709983002/diff/40001/pkg/front_end/lib/src/f...
File pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart (right):

https://codereview.chromium.org/2709983002/diff/40001/pkg/front_end/lib/src/f...
pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart:1190: // characters.
On 2017/02/23 12:47:35, ahe wrote:
> I don't understand this comment. It seems like you do use the hint.

Sorry that was a left over, will remove it.

[kustermann, 2017-02-24 14:54:47]

I did the experiment we talked about offline and saw no significant difference,
within flaky range.

[kustermann, 2017-02-24 16:03:46]

Description was changed from

==========
fasta: Use more efficient Uint16List/Uint32List for line offset information, use
hints for length
==========

to

==========
fasta: Use more efficient Uint16List/Uint32List for line offset information, use
hints for length

R=ahe@google.com

Committed:
https://github.com/dart-lang/sdk/commit/a94bd171687d5a56aa84e6cf27ada540dad2bed5
==========

[kustermann, 2017-02-24 16:03:47]

Committed patchset #3 (id:60001) manually as
a94bd171687d5a56aa84e6cf27ada540dad2bed5 (presubmit successful).