From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v2 18/30] libxl: ocaml: use the "string
 option" type for IDL strings
Date: Thu, 13 Jun 2013 16:58:59 +0100
Message-ID: <51B9EC43.2030000@citrix.com>
References: <1371137112-16692-1-git-send-email-rob.hoes@citrix.com>
	<1371137112-16692-19-git-send-email-rob.hoes@citrix.com>
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To: Rob Hoes <rob.hoes@citrix.com>
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On 13/06/13 16:25, Rob Hoes wrote:
> The libxl IDL is based on C type "char *", and therefore "strings" can
> by NULL, or be an actual string. In ocaml, it is common to encode such

"can be NULL" perhaps?

~Andrew

> things as option types.
>
> Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
> ---
>  tools/ocaml/libs/xl/genwrap.py       |    2 +-
>  tools/ocaml/libs/xl/xenlight_stubs.c |   21 +++++++++++++++++++++
>  2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/tools/ocaml/libs/xl/genwrap.py b/tools/ocaml/libs/xl/genwrap.py
> index f0d4885..d967ee6 100644
> --- a/tools/ocaml/libs/xl/genwrap.py
> +++ b/tools/ocaml/libs/xl/genwrap.py
> @@ -8,7 +8,7 @@ import idl
>  builtins = {
>      "bool":                 ("bool",                   "%(c)s = Bool_val(%(o)s)",           "Val_bool(%(c)s)" ),
>      "int":                  ("int",                    "%(c)s = Int_val(%(o)s)",            "Val_int(%(c)s)"  ),
> -    "char *":               ("string",                 "%(c)s = dup_String_val(%(o)s)", "caml_copy_string(%(c)s)"),
> +    "char *":               ("string option",          "%(c)s = String_option_val(%(o)s)",  "Val_string_option(%(c)s)"),
>      "libxl_domid":          ("domid",                  "%(c)s = Int_val(%(o)s)",            "Val_int(%(c)s)"  ),
>      "libxl_devid":          ("devid",                  "%(c)s = Int_val(%(o)s)",            "Val_int(%(c)s)"  ),
>      "libxl_defbool":        ("bool option",            "%(c)s = Defbool_val(%(o)s)",        "Val_defbool(%(c)s)" ),
> diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c b/tools/ocaml/libs/xl/xenlight_stubs.c
> index 7b7d696..e801643 100644
> --- a/tools/ocaml/libs/xl/xenlight_stubs.c
> +++ b/tools/ocaml/libs/xl/xenlight_stubs.c
> @@ -371,6 +371,27 @@ static value Val_hwcap(libxl_hwcap *c_val)
>  	CAMLreturn(hwcap);
>  }
>  
> +static value Val_string_option(const char *c_val)
> +{
> +	CAMLparam0();
> +	CAMLlocal2(tmp1, tmp2);
> +	if (c_val) {
> +		tmp1 = caml_copy_string(c_val);
> +		tmp2 = Val_some(tmp1);
> +		CAMLreturn(tmp2);
> +	}
> +	else
> +		CAMLreturn(Val_none);
> +}
> +
> +static char *String_option_val(value v)
> +{
> +	char *s = NULL;
> +	if (v != Val_none)
> +		s = dup_String_val(Some_val(v));
> +	return s;
> +}
> +
>  #include "_libxl_types.inc"
>  
>  #define _STRINGIFY(x) #x