[plt-scheme] reading a whole file

Now that's good for the cookbook.


On Nov 4, 2008, at 11:11 AM, Robby Findler wrote:

> Okay, I got curious. Below are some timing tests that suggest that,
> when it is possible, reading the file into a string has more
> consistent performance. Matching directly on the port can be much
> faster if the match is near the beginning of the file, but much worse
> if it is at the end of the file. The code is below. The file in
> question is 96k in size.
>
> This is the output I get (on a mac 2.8ghz intel w/ a pretty fast  
> filesystem):
>
> Welcome to DrScheme, version 4.1.2.2-svn3nov2008 [3m].
> Language: Module; memory limit: 128 megabytes.
> port/beginning-of-file
> cpu time: 11 real time: 11 gc time: 0
> string/beginning-of-file
> cpu time: 180 real time: 180 gc time: 30
> port/end-of-file
> cpu time: 2695 real time: 2715 gc time: 0
> string/end-of-file
> cpu time: 226 real time: 226 gc time: 10
>>
>
> Robby
>
> #lang scheme
> (require scheme/port)
>
> (define ((check-matches-port file) r)
>   (call-with-input-file file
>     (λ (port)
>       (regexp-match r port))))
>
> (define (check-matches-string file)
>   (let ([s
>          (let ([sp (open-output-string)])
>            (call-with-input-file file
>              (λ (fp)
>                (copy-port fp sp)))
>            (get-output-string sp))])
>     (λ (r)
>       (regexp-match r s))))
>
> (define (test check-matches reg)
>   (time
>    (let ([matcher (check-matches (build-path (collection-path  
> "framework")
>                                              "private"
>                                              "frame.ss"))])
>      (let loop ([n 300])
>        (unless (zero? n)
>          (matcher reg)
>          (loop (- n 1)))))))
>
> 'port/beginning-of-file
> (test check-matches-port #rx"unit")
>
> 'string/beginning-of-file
> (test check-matches-string #rx"unit")
>
>
> 'port/end-of-file
> (test check-matches-port #rx"pasteboard-mixin open-here%")
>
> 'string/end-of-file
> (test check-matches-string #rx"pasteboard-mixin open-here%")
>
>
> On Tue, Nov 4, 2008 at 11:00 AM, Shriram Krishnamurthi  
> <sk at cs.brown.edu> wrote:
>> Yes if you're doing only one string.  It's nice to be able to say
>>
>>  (define c ...contents of file...)
>>
>>  (match ... c)
>>  (match ... c)
>>
>> as you formulate and test hypotheses about the content of the file.
>> That is, it's nice to type the code to get the file content just  
>> once,
>> rather than over and over again.
>>
>> Shriram
>>
>>
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