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From: Jon Harrop <jon@ffconsultancy.com>
Organization: Flying Frog Consultancy Ltd.
To: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] Re: Threads performance issue.
Date: Tue, 17 Feb 2009 11:33:03 +0000
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References: <2184b2340902160715y1f935b5ehc0e6195b3f75b66b@mail.gmail.com> <20090217102659.GD29651@janestcapital.com> <2184b2340902170250g75d4482bt1d49e0e295c2e6d7@mail.gmail.com>
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X-Spam: no; 0.00; bigarray:01 ocaml:01 ocaml:01 desc:01 desc:01 stdlib:01 parser:01 2009:98 increments:98 frog:98 threads:01 char:01 char:01 wrote:01 unix:01 

On Tuesday 17 February 2009 10:50:44 R=C3=A9mi Dewitte wrote:
> Memory mapping of the file could be done using BigArray or do I have to
> write C code ?

You can memory map files very easily entirely from within OCaml.

This was actually covered in the OCaml Journal article about OpenGL 2, whic=
h=20
used file mapping as an easy way to load texture maps. First, you open the=
=20
file to create a file descriptor:

  try_finally (Unix.openfile file [] 777)

Then you map the file to create a big array:

    (fun desc ->
       let source =3D Array1.map_file desc int8_signed c_layout false (-1) =
in

Then you can do something with the big array, like copy it into an ordinary=
=20
string:

       String.init (Array1.dim source) (fun i -> Char.chr source.{i}))

=46inally, you close the file:

    Unix.close

Note that I have used try_finally and String.init functions from my own std=
lib=20
but their purpose and use should be obvious.

You probably just want to replace read_char with a function that increments=
 a=20
counter and reads from the array, with the whole parser inside the=20
try_finally.

=2D-=20
Dr Jon Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/?e