code review 170044: syscalls can return negative i/o counts. fix bugs in Re...

syscalls can return negative i/o counts. fix bugs in ReadAt and WriteAt not to include
negative counts in return values.

[r, 2009-12-09 22:06:01]

Hello rsc (cc: golang-dev@googlegroups.com),

I'd like you to review the following change.

[rsc, 2009-12-09 22:07:06]

LGTM

[hurtonm, 2009-12-09 22:12:46]

Hi,

Is it possible for Pread syscall to return positive count and nonzero
error? If not, I think we could make the code a little simpler.

- Martin

On Wed, Dec 9, 2009 at 11:06 PM,  <r@golang.org> wrote:
> Reviewers: rsc,
>
> Message:
> Hello rsc (cc: golang-dev@googlegroups.com),
>
> I'd like you to review the following change.
>
>
> Description:
> syscalls can return negative i/o counts. fix bugs in ReadAt and WriteAt
> not to include
> negative counts in return values.
>
> Please review this at http://codereview.appspot.com/170044
>
> Affected files:
>  M src/pkg/os/file.go
>
>
> Index: src/pkg/os/file.go
> ===================================================================
> --- a/src/pkg/os/file.go
> +++ b/src/pkg/os/file.go
> @@ -141,7 +141,9 @@
>                if m == 0 && e == 0 {
>                        return n, EOF
>                }
> -               n += m;
> +               if m > 0 {
> +                       n += m
> +               }
>                if e != 0 {
>                        err = &PathError{"read", file.name, Errno(e)};
>                        break;
> @@ -186,7 +188,9 @@
>        }
>        for len(b) > 0 {
>                m, e := syscall.Pwrite(file.fd, b, off);
> -               n += m;
> +               if m > 0 {
> +                       n += m
> +               }
>                if e != 0 {
>                        err = &PathError{"write", file.name, Errno(e)};
>                        break;
>
>
>

[r, 2009-12-09 22:18:37]

*** Submitted as http://code.google.com/p/go/source/detail?r=1502f7952a23 ***

syscalls can return negative i/o counts. fix bugs in ReadAt and WriteAt not to
include
negative counts in return values.

R=rsc
CC=golang-dev
http://codereview.appspot.com/170044