From: "Berger, Daniel" <Daniel.Berger@...>
Date: 2006-05-19T04:29:31+09:00
Subject: Re: String#nstrip ?

> -----Original Message-----
> From: Joel VanderWerf [mailto:vjoel@path.berkeley.edu] 
> Sent: Thursday, May 18, 2006 12:41 PM
> To: ruby-core@ruby-lang.org
> Subject: Re: String#nstrip ?
> 
> 
> Daniel Berger wrote:
> > Hi all,
> > 
> > When using the Win32API package, I often have to resort to 
> this idiom 
> > to get a string out of a buffer:
> > 
> > string.split(0.chr).first
> 
> Why won't slice do the trick?
> 
> irb(main):001:0> s = "hello\0\0\0\0"
> => "hello\000\000\000\000"
> irb(main):002:0> s[/^.*?(?=\0)/]
> => "hello"
> 
> -- 
>       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

> -----Original Message-----
> From: ara.t.howard@noaa.gov [mailto:ara.t.howard@noaa.gov] 
> Sent: Thursday, May 18, 2006 1:16 PM
> To: ruby-core@ruby-lang.org
> Subject: Re: String#nstrip ?
> 
> 
> On Fri, 19 May 2006, Daniel Berger wrote:
> 
> > Hi all,
> >
> > When using the Win32API package, I often have to resort to 
> this idiom 
> > to get
> > a string out of a buffer:
> >
> > string.split(0.chr).first
> >
> > The problem is that it's kinda slow.  No, I can't use 
> String#rstrip or
> > String#gsub because often there's other junk at the end of 
> the string that 
> > would prevent those methods from working.
> >
> > What about adding a String#nstrip (null strip) method that would 
> > return a
> > string up to the first NULL character?  Here's a simple 
> implementation:
> 
> harp:~ > ruby -e'  p "42\0\0"[ /^[^\0]*/ ]  '
> "42"
> 
> harp:~ > ruby -e'  p "42"[ /^[^\0]*/ ]  '
> "42"
> 
> harp:~ > ruby -e'  p ""[ /^[^\0]*/ ]  '
> ""

Thanks all.  My benchmarks show the best solutions at about ~4x faster.
I've included a few other solutions folks have provided.

require 'benchmark'

MAX = 100000
STRING = "hello\0\0\0\0m"

Benchmark.bm do |x|
   x.report("String#split"){
      MAX.times{ STRING.split("\0").first }
   }

   # Another attempt by me
   x.report("String#index"){
      MAX.times{ STRING[0 .. STRING.index(0.chr)-1] }
   }

   # Hugh Sasse
   x.report("String#scan"){
      MAX.times{ STRING.scan(/^[^\000]+/).first }
   }

   # Joel VanderWerf
   x.report("String#[regex1]"){
      MAX.times{ STRING[/^.*?(?=\0)/] }
   }

   # Ara Howard
   x.report("String#[regex2]"){
      MAX.times{ STRING[ /^[^\0]*/ ] }
   }
end

String#split  3.174000   0.000000   3.174000 (  3.355000)
String#index  1.733000   0.000000   1.733000 (  2.023000)
String#scan  1.141000   0.000000   1.141000 (  1.212000)
String#[regex1]  0.822000   0.010000   0.832000 (  0.901000)
String#[regex2]  0.691000   0.000000   0.691000 (  0.741000)

Not *quite* as fast as the C version, but good enough I suppose.

Ok, nevermind. :)

Dan


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