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From: Joel Reymont <joelr1@gmail.com>
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Date: Wed, 19 Jan 2011 19:47:03 +0000
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Subject: [Caml-list] accessing a bigarray from c stubs

Folks,

How do I get hold of the array pointer in the C stub below, assuming that the Caml value is of type (char, Bigarray.int8_unsigned_elt) Bigarray.kind?

Should I be using Bigarray for memory buffers?

	Thanks in advance, Joel

---

/*
int bg_usb480_read (
    Beagle beagle,
    u32 *  status,
    u32 *  events,
    u64 *  time_sop,
    u64 *  time_duration,
    u32 *  time_dataoffset,
    int    max_bytes,
    u08 *  packet
);
*/

type buffer = (char, Bigarray.int8_unsigned_elt) Bigarray.kind

CAMLprim value ml_bg_usb480_read(value beagle, value bytes, value buffer)
{
  CAMLparam3(beagle, bytes, buffer);
  CAMLlocal1(tuple);

  u32 status, events, time_dataoffset;
  u64 time_sop, time_duration;
  int max_bytes = Int_val(bytes);
  u08 *packet = ???
  
  int err = bg_usb480_read(Int_val(beagle), &status, &events, 
                           &time_sop, &time_duration, &time_dataoffset,
                           Int_val(max_bytes), packet);

  tuple = caml_alloc_tuple(6);
  Store_field(tuple, 0, Val_int(err));
  Store_field(tuple, 1, Val_int32(status));
  Store_field(tuple, 2, Val_int32(events));
  Store_field(tuple, 3, Val_int64(time_sop));
  Store_field(tuple, 4, Val_int64(time_duration));
  Store_field(tuple, 5, Val_int32(time_dataoffset));

  CAMLreturn(tuple);
}

---
http://wagerlabs.com | @wagerlabs | http://www.linkedin.com/in/joelreymont