[Libguestfs] [nbdkit PATCH v2 08/24] ocaml: Implement .cache script callback

[Richard W.M. Jones]

On Wed, May 15, 2019 at 10:57:58PM -0500, Eric Blake wrote:
> +static int
> +can_cache_wrapper (void *h)
> +{
> +  CAMLparam0 ();
> +  CAMLlocal1 (rv);
> +
> +  caml_leave_blocking_section ();
> +
> +  rv = caml_callback_exn (can_cache_fn, *(value *) h);
> +  if (Is_exception_result (rv)) {
> +    nbdkit_error ("%s", caml_format_exception (Extract_exception (rv)));
> +    caml_enter_blocking_section ();
> +    CAMLreturnT (int, -1);
> +  }
> +
> +  caml_enter_blocking_section ();
> +  CAMLreturnT (int, Int_val (rv));

The not very obvious implicit assumption here is that the order of the
Cache* flags in the OCaml code is the same as the numbering of the
NBDKIT_CACHE_* flags in the C code, which it is, so we should be good.

Rich.

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