code review 4625068: io.WriteString: if the object has a WriteString method,...

io.WriteString: if the object has a WriteString method, use it

This avoids allocation when writing to bytes.Buffers and bufio.Writers, for
example.

[eds, 2011-06-26 08:28:11]

Hello golang-dev@googlegroups.com,

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

[rsc, 2011-06-27 13:55:32]

I'm pretty skeptical.  How often does this come up?

Russ

[eds, 2011-06-27 20:17:23]

On Tue, Jun 28, 2011 at 1:55 AM, Russ Cox <rsc@golang.org> wrote:
> I'm pretty skeptical.  How often does this come up?

It could come up a few times in the standard library. WriteString is
called in about 50 places outside of tests.

I think WriteString needs to earn its keep and it's not doing that
right now. Alternatively, I propose removing WriteString. It was once
useful before strings could be converted to []bytes, but now it's
actually a little more verbose than using a conversion:

io.WriteString(w, s)
vs
w.Write([]byte(s))

- Evan

[rsc, 2011-06-27 20:20:52]

> Alternatively, I propose removing WriteString.

Fine with me.
Let's wait and see what Rob thinks.

[r2, 2011-06-27 21:39:27]

On 28/06/2011, at 6:20 AM, Russ Cox wrote:

>> Alternatively, I propose removing WriteString.
> 
> Fine with me.
> Let's wait and see what Rob thinks.

bytes.Buffer.WriteString is significantly more efficient than the conversion.
ditto for bufio. i propose that io.WriteString gain the ability to use those
implementations, as proposed, and that the real question is whether StringWriter
be published. since its first and only customer for now will be io.WriteString,
let's just do it locally and see, as with RuneReader, if pressure to publish
grows.

-rob

[Kyle C, 2011-06-28 00:29:12]

On Mon, Jun 27, 2011 at 2:39 PM, Rob 'Commander' Pike <r@google.com> wrote:

>
> On 28/06/2011, at 6:20 AM, Russ Cox wrote:
>
> >> Alternatively, I propose removing WriteString.
> >
> > Fine with me.
> > Let's wait and see what Rob thinks.
>
> bytes.Buffer.WriteString is significantly more efficient than the
> conversion. ditto for bufio. i propose that io.WriteString gain the ability
> to use those implementations, as proposed, and that the real question is
> whether StringWriter be published. since its first and only customer for now
> will be io.WriteString, let's just do it locally and see, as with
> RuneReader, if pressure to publish grows.
>

os.File.WriteString looks to be less efficient than Write([]byte(s)), so
that may be a candidate for removal.

[r2, 2011-06-28 01:07:37]

http://codereview.appspot.com/4639081

[eds, 2011-06-28 05:09:50]

Hello golang-dev@googlegroups.com, rsc@golang.org, r@google.com,
consalus@gmail.com (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2011-06-28 05:14:14]

http://codereview.appspot.com/4625068/diff/1004/src/pkg/io/io.go
File src/pkg/io/io.go (right):

http://codereview.appspot.com/4625068/diff/1004/src/pkg/io/io.go#newcode203
src/pkg/io/io.go:203: // WriteString must return a non-nil error if it returns n
< len(s).
there's an unnecessary amount of explanation here for a private nonce interface.
if it belongs anywhere, a shorter version could go onto io.WriteString

[eds, 2011-06-28 05:15:15]

Hello golang-dev@googlegroups.com, rsc@golang.org, r@google.com,
consalus@gmail.com, r@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2011-06-28 05:24:34]

the CL desc I see isn't right. have you updated it locally?

[eds, 2011-06-28 05:30:11]

On Tue, Jun 28, 2011 at 5:24 PM,  <r@golang.org> wrote:
> the CL desc I see isn't right. have you updated it locally?

Updated in the CL (after you looked).

- Evan

[r, 2011-06-28 06:01:07]

it's good to provide actual information in the CL description. these
descriptions are a matter of record and should be helpful and searchable.

io.WriteString: if the object implements the WriteString method, use that.
Avoids allocation when writing to bytes.Buffers, bufio.Writers, etc.

[eds, 2011-06-28 06:05:31]

Hello golang-dev@googlegroups.com, rsc@golang.org, r@google.com,
consalus@gmail.com, r@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2011-06-28 06:06:31]

LGTM

[r, 2011-06-28 06:10:45]

*** Submitted as http://code.google.com/p/go/source/detail?r=5e7ad769e69f ***

io.WriteString: if the object has a WriteString method, use it

This avoids allocation when writing to bytes.Buffers and bufio.Writers, for
example.

R=golang-dev, rsc, r, consalus, r
CC=golang-dev
http://codereview.appspot.com/4625068

Committer: Rob Pike <r@golang.org>