[plt-scheme] Re: gzipped file + pipe hangs at the end

Update -

I was able to isolate the problem to just the pipe.

(define-values (in out)
  (make-pipe #f))
(write-bytes #"this is a test" out)
(read-bytes 14 in) ;; reads out #"this is a test"
(read-bytes 1 in) ;; hangs.

It seems that unlike regular input-port, pipe does not produce #<eof> in
this situation.  How can I make the pipe generate #<eof>?

Thanks,
yc

On Thu, Sep 3, 2009 at 7:37 PM, YC <yinso.chen at gmail.com> wrote:

> Hi -
>
> I am trying to pipe a gzipped file and it seems to hang at the end when I
> am trying to read the data.  It's unclear to me why it hangs at the end (I
> observed this by seeing it hangs immediately with small files, read quite a
> bit of data with medium files, and read lots of data with large files before
> it hangs), and hopefully others can see what I am missing here.
>
> Thanks,
> yc
>
> ;; gzip.ss
> #lang scheme/base
> (require file/gunzip file/gzip mzlib/trace scheme/port)
>
> (define (open-gzip-file path)
>   (let-values (((in out)
>                 (make-pipe-with-specials #f path)))
>     (thread (lambda ()
>               (call-with-input-file path
>                 (lambda (in)
>                   (gunzip-through-ports in out)))))
>     in))
>
> (define (read-bytes* num in)
>     (read-bytes num in))
>
> (trace read-bytes*)
>
> (define (reader in)
>   (let loop ((b (read-bytes* 4096 in)))
>     (if (eof-object? b)
>         ;; (reverse acc)
>         (void)
>         (loop (read-bytes* 4096 in)))))
>
> (provide reader open-gzip-file)
>
> ;; test ;; uncomment and run the two lines below in REPL
> ;; (require "gzip.ss")
> ;; (reader (open-gzip-file path-to-gzipped-file))
> ;; observe the it eventually hangs on calling read-bytes*.
>
>
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