code review 8100044: go/printer: use strings.Split instead of specialized code

go/printer: use strings.Split instead of specialized code

With the faster strings package, the difference between
the specialized code and strings.Split is in the noise:

benchmark         old ns/op    new ns/op    delta
BenchmarkPrint     16724291     16686729   -0.22%

(Measured on a Mac Pro, 2.8GHz Quad-core Intel Xeon,
4GB 800 MHz DDR2, Mac OS X 10.8.3)

[gri, 2013-03-28 22:40:08]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go

[bradfitz, 2013-03-28 22:46:49]

LGTM

On Thu, Mar 28, 2013 at 3:40 PM, <gri@golang.org> wrote:

> Reviewers: golang-dev1,
>
> Message:
> Hello golang-dev@googlegroups.com,
>
> I'd like you to review this change to
> https://code.google.com/p/go
>
>
> Description:
> go/printer: use strings.Split instead of specialized code
>
> With the faster strings package, the difference between
> the specialized code and strings.Split is in the noise:
>
> benchmark         old ns/op    new ns/op    delta
> BenchmarkPrint     16724291     16686729   -0.22%
>
> (Measured on a Mac Pro, 2.8GHz Quad-core Intel Xeon,
> 4GB 800 MHz DDR2, Max OS X 10.8.3).
>
> Please review this at
https://codereview.appspot.**com/8100044/<https://codereview.appspot.com/8100...
>
> Affected files:
>   M src/pkg/go/printer/printer.go
>
>
> Index: src/pkg/go/printer/printer.go
> ==============================**==============================**=======
> --- a/src/pkg/go/printer/printer.**go
> +++ b/src/pkg/go/printer/printer.**go
> @@ -395,35 +395,6 @@
>         }
>  }
>
> -// Split comment text into lines
> -// (using strings.Split(text, "\n") is significantly slower for
> -// this specific purpose, as measured with: go test -bench=Print)
> -//
> -func split(text string) []string {
> -       // count lines (comment text never ends in a newline)
> -       n := 1
> -       for i := 0; i < len(text); i++ {
> -               if text[i] == '\n' {
> -                       n++
> -               }
> -       }
> -
> -       // split
> -       lines := make([]string, n)
> -       n = 0
> -       i := 0
> -       for j := 0; j < len(text); j++ {
> -               if text[j] == '\n' {
> -                       lines[n] = text[i:j] // exclude newline
> -                       i = j + 1            // discard newline
> -                       n++
> -               }
> -       }
> -       lines[n] = text[i:]
> -
> -       return lines
> -}
> -
>  // Returns true if s contains only white space
>  // (only tabs and blanks can appear in the printer's context).
>  //
> @@ -616,7 +587,7 @@
>
>         // for /*-style comments, print line by line and let the
>         // write function take care of the proper indentation
> -       lines := split(text)
> +       lines := strings.Split(text, "\n")
>
>         // The comment started in the first column but is going
>         // to be indented. For an idempotent result, add indentation
>
>
> --
>
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>
>

[gri, 2013-03-28 22:47:43]

*** Submitted as https://code.google.com/p/go/source/detail?r=5e794a4e3035 ***

go/printer: use strings.Split instead of specialized code

With the faster strings package, the difference between
the specialized code and strings.Split is in the noise:

benchmark         old ns/op    new ns/op    delta
BenchmarkPrint     16724291     16686729   -0.22%

(Measured on a Mac Pro, 2.8GHz Quad-core Intel Xeon,
4GB 800 MHz DDR2, Mac OS X 10.8.3)

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/8100044