/* Memory info command for virtual domains.
   (C) Copyright 2008 Richard W.M. Jones, Red Hat Inc.
   http://libvirt.org/

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

   This contains hand-coded C functions written for speed.
*/

#include <config.h>

#include <string.h>

#include <caml/config.h>
#include <caml/alloc.h>
#include <caml/memory.h>
#include <caml/mlvalues.h>
#include <caml/bigarray.h>

CAMLprim value
virt_mem_mmap_find_in (value startv, value alignv, value strv, value arrv)
{
  CAMLparam4 (startv, alignv, strv, arrv);
  CAMLlocal2 (rv, vv);
  long start = Long_val (startv); /* Start offset for search. */
  long align = Long_val (alignv); /* Alignment for search. */
  char *str = String_val (strv);  /* String to search for. */
  int strlen = caml_string_length (strv);
  void *data = Data_bigarray_val (arrv); /* Data in bigarray. */
  int datalen = Bigarray_val(arrv)->dim[0]; /* Total length of bigarray. */
  long i, r = -1;
  void *p;

  /* memmem is a GNU extension.  Note that we cannot use strstr because
   * OCaml strings may contain NULs, and in this case it is very likely
   * that it does contain NULs.
   */
#ifdef HAVE_MEMMEM
  if (align == 1) {
    p = memmem (data+start, datalen-start, str, strlen);
    r = p ? p-data : -1;
    goto ret;
  }
#endif

  p = data+start;
  for (i = start; i < datalen-strlen; i += align) {
    if (memcmp (p, str, strlen) == 0) {
      r = p-data;
      goto ret;
    }
    p += align;
  }

 ret:
  if (r == -1)
    rv = Val_int (0);		/* None */
  else {
    vv = Val_long (r);		/* Some r */
    rv = caml_alloc (1, 0);
    Store_field (rv, 0, vv);
  }

  CAMLreturn (rv);
}