Speed up ASCII, LATIN1, UTF8 converters, for single-byte codeunits.

Speed up ASCII, LATIN1, UTF8 converters, for single-byte values.

In case of Uint8Lists, LATIN1 is now simply calling
String.fromCharCodes, skipping all checks.

BUG=https://code.google.com/p/dart/issues/detail?id=17659
R=lrn@google.com

Committed: https://code.google.com/p/dart/source/detail?r=34300

[kevmoo, 2014-03-23 23:17:31]

On 2014/03/23 08:07:59, Anders Johnsen wrote:

I'd LOVE this to get in, BUT...this will break on IE9 due to dart:typed_data and
we're still supporting IE9 through at least 1.5.

[Anders Johnsen, 2014-03-24 07:38:52]

It was my understanding that the types are defined, but allocation will fail on
IE9 - is that not the case?

If not, I'll pull out that part of the code - it's still a lot faster for Latin1
:)

[Lasse Reichstein Nielsen, 2014-03-24 09:21:00]

lgtm

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/latin1.dart
File sdk/lib/convert/latin1.dart (right):

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/latin1.d...
sdk/lib/convert/latin1.dart:129: // solution can be made.
Is it still incredibly stupid, or can we downgrade it to moderately stupid?

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/latin1.d...
sdk/lib/convert/latin1.dart:140: if (source is Uint8List || source is Int8List)
{
Int8List isn't safe. It can contain negative numbers.
Luckily code that works with bytes will likely use Uint8List for everything.

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/utf.dart
File sdk/lib/convert/utf.dart (right):

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/utf.dart...
sdk/lib/convert/utf.dart:509: addSingleBytes(i - singleBytesCount - 1, i - 1);
i - 1 - singleBytesCount

Allows reuse of the (i - 1) computation.
Ditto above.

[Lasse Reichstein Nielsen, 2014-03-24 09:30:38]

This should work on IE9 too.
The test is redundant, since there will never be an Uint8List instance, but it
should still work.

The problem with IE9 is only in using the typed lists, not in using the types.

[Anders Johnsen, 2014-03-24 12:01:01]

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/latin1.dart
File sdk/lib/convert/latin1.dart (right):

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/latin1.d...
sdk/lib/convert/latin1.dart:129: // solution can be made.
On 2014/03/24 09:21:01, Lasse Reichstein Nielsen wrote:
> Is it still incredibly stupid, or can we downgrade it to moderately stupid?

Done.

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/latin1.d...
sdk/lib/convert/latin1.dart:140: if (source is Uint8List || source is Int8List)
{
On 2014/03/24 09:21:01, Lasse Reichstein Nielsen wrote:
> Int8List isn't safe. It can contain negative numbers.
> Luckily code that works with bytes will likely use Uint8List for everything.

Done.

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/utf.dart
File sdk/lib/convert/utf.dart (right):

https://codereview.chromium.org/208693008/diff/40001/sdk/lib/convert/utf.dart...
sdk/lib/convert/utf.dart:509: addSingleBytes(i - singleBytesCount - 1, i - 1);
On 2014/03/24 09:21:01, Lasse Reichstein Nielsen wrote:
> i - 1 - singleBytesCount
> 
> Allows reuse of the (i - 1) computation.
> Ditto above.

Done.

[Anders Johnsen, 2014-03-24 12:01:52]

Committed patchset #4 manually as r34300 (presubmit successful).