code review 81480043: bytes, strings: allow Reader.Seek past 1<<31 on 64-bit ...

bytes, strings: allow Reader.Seek past 1<<31 on 64-bit machines

Fixes Issue 7654

[bradfitz, 2014-03-27 15:42:45]

Hello golang-codereviews@googlegroups.com (cc: iant@golang.org, rsc@golang.org),

I'd like you to review this change to
https://go.googlecode.com/hg/

[rsc, 2014-03-27 15:48:45]

https://codereview.appspot.com/81480043/diff/40001/src/pkg/bytes/reader.go
File src/pkg/bytes/reader.go (right):

https://codereview.appspot.com/81480043/diff/40001/src/pkg/bytes/reader.go#ne...
src/pkg/bytes/reader.go:119: const intSize = 32 << uint(^uint(0)>>63)
if int64(int(abs)) != abs {

[bradfitz, 2014-03-27 16:04:26]

That is nicer. But while I'm here, can I just fix the Seeker completely? It
should be possible to seek to large int64 positions even on 32-bit
platforms, just as it's possible to seek past EOF.  All Reads are just then
EOF, regardless if you're at offset 100 in a 50 byte file or offset 1 << 50.

I don't know why we have this arbitrary 2GB boundary on 32-bit machines. It
looks like it was only to save ~two if statements.



On Thu, Mar 27, 2014 at 8:48 AM, <rsc@golang.org> wrote:

>
> https://codereview.appspot.com/81480043/diff/40001/src/pkg/bytes/reader.go
> File src/pkg/bytes/reader.go (right):
>
> https://codereview.appspot.com/81480043/diff/40001/src/
> pkg/bytes/reader.go#newcode119
> src/pkg/bytes/reader.go:119: const intSize = 32 << uint(^uint(0)>>63)
> if int64(int(abs)) != abs {
>
> https://codereview.appspot.com/81480043/
>

[rsc, 2014-03-27 16:08:30]

ok

[bradfitz, 2014-03-27 18:47:10]

R=close

Superseded by https://codereview.appspot.com/81530043