Re: [Chicken-users] using mmap files as strings?

[Alan Post]

I've summarized this information and created an mmap example on the
wiki:

  http://wiki.call-cc.org/manual/Unit%20posix#memory-mapped-io-example

I'm afraid to ask, for being told to do it myself, but the ability to
edit single docment sections rather than whole documents would be very
nice.

-Alan

On Sat, Oct 23, 2010 at 08:11:20PM -0500, Jim Ursetto wrote:
> On Sat, Oct 23, 2010 at 05:04, Peter Bex <address@hidden> wrote:
> > On Fri, Oct 22, 2010 at 05:58:02PM -0600, Alan Post wrote:
> >> This is excellent, I've learned a lot more about how all of this
> >> works together now.
> >>
> >> What method would I use to convert a pointer and a length to a
> >> string?  Even though I'm copying the memory, how do I do it at
> >> all?
> >
> > Something like this:
> >
> > {
> >  C_word *scheme_string;
> >
> >  scheme_string = C_alloc(C_SIZEOF_STRING(the_length));
> >  C_string(&scheme_string, the_length, the_pointer);
> >  C_kontinue(the_continuation, scheme_string);
> > }
> 
> I think this might be better:
> 
> (let ((to (make-string len))
>  (move-memory! from to len))
> 
> Using your original example,
> 
> (use posix lolevel)
> 
> (let* ((fd (file-open "mmap.scm" (+ open/rdonly open/nonblock)))
>        (size (file-size fd))
>        (mmap (map-file-to-memory #f size prot/read (+ map/file map/shared) 
> fd))
>        (buf  (memory-mapped-file-pointer mmap)))
>   (let* ((len 10)
>           (str (make-string len)))
>     (move-memory! buf str len)
>     (print str)))
> 
> $ csi -script mmap.scm
> (use posix
> 
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