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Re: [Libguestfs] [PATCH 3/7] generator: Add new return types to ABI: RLenNode and RLenValue



There are still a few mistakes.  See my comments inline.

> From 02ce84fd959bf67afc6999eaeecef78ccdf57c71 Mon Sep 17 00:00:00 2001
> From: Alex Nelson <ajnelson cs ucsc edu>
> Date: Tue, 6 Sep 2011 09:27:51 -0700
> Subject: [PATCH] generator: Add new return type to ABI: RLenValue
> 
> RLenValue is are similar to RLenType, though with one less argument.
> This required adding one processing function for OCaml and Python.
> 
> Signed-off-by: Alex Nelson <ajnelson cs ucsc edu>
> ---
>  generator/generator.ml |   69 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 69 insertions(+), 0 deletions(-)
> 
> diff --git a/generator/generator.ml b/generator/generator.ml
> index b6fb8b3..2703023 100755
> --- a/generator/generator.ml
> +++ b/generator/generator.ml
> @@ -51,6 +51,7 @@ and ret =
>    | RNodeList                           (* Returns hive_node_h* or NULL. *)
>    | RValue                              (* Returns hive_value_h or 0. *)
>    | RValueList                          (* Returns hive_value_h* or NULL. *)
> +  | RLenValue                           (* See value_struct_length. *)

I think the comment should read "see value_data_cell_offset", but I'd
prefer it if the comment was "Returns offset and length of value"
since that describes what it actually does.

>    | RString                             (* Returns char* or NULL. *)
>    | RStringList                         (* Returns char** or NULL. *)
>    | RLenType                            (* See hivex_value_type. *)
> @@ -890,6 +891,7 @@ and generate_c_prototype ?(extern = false) name style =
>     | RValueList -> pr "hive_value_h *"
>     | RString -> pr "char *"
>     | RStringList -> pr "char **"
> +   | RLenValue -> pr "hive_value_h "
>     | RLenType -> pr "int "
>     | RLenTypeVal -> pr "char *"
>     | RInt32 -> pr "int32_t "
> @@ -911,6 +913,7 @@ and generate_c_prototype ?(extern = false) name style =
>    ) (snd style);
>    (match fst style with
>     | RLenType | RLenTypeVal -> pr ", hive_type *t, size_t *len"
> +   | RLenValue -> pr ", size_t *len"
>     | _ -> ()
>    );
>    pr ");\n"
> @@ -1113,6 +1116,10 @@ On error this returns NULL and sets errno.\n\n"
>             pr "\
>  Returns 0 on success.
>  On error this returns -1 and sets errno.\n\n"
> +       | RLenValue ->
> +           pr "\
> +Returns a positive number on success.
> +On error this returns 0 and sets errno.\n\n"

This should be:

  Returns a value handle.
  On error this returns 0 and sets errno.\n\n"

> @@ -1687,6 +1695,7 @@ static hive_type HiveType_val (value);
>  static value Val_hive_type (hive_type);
>  static value copy_int_array (size_t *);
>  static value copy_type_len (size_t, hive_type);
> +static value copy_len (size_t);
>  static value copy_type_value (const char *, size_t, hive_type);
>  static void raise_error (const char *) Noreturn;
>  static void raise_closed (const char *) Noreturn;
> @@ -1709,6 +1718,7 @@ static void raise_closed (const char *) Noreturn;
>        let c_params =
>          match fst style with
>          | RLenType | RLenTypeVal -> c_params @ [["&t"; "&len"]]
> +        | RLenValue -> c_params @ [["&len"]]
>          | _ -> c_params in
>        let c_params = List.concat c_params in
>  
> @@ -1781,6 +1791,10 @@ static void raise_closed (const char *) Noreturn;
>              pr "  size_t len;\n";
>              pr "  hive_type t;\n";
>              "-1"
> +        | RLenValue ->
> +            pr "  int r;\n";
> +            pr "  size_t len;\n";
> +            "0"

'r' is not an int.  It's a hive_value_h.

>          | RLenTypeVal ->
>              pr "  char *r;\n";
>              pr "  size_t len;\n";
> @@ -1861,6 +1875,7 @@ static void raise_closed (const char *) Noreturn;
>             pr "  for (int i = 0; r[i] != NULL; ++i) free (r[i]);\n";
>             pr "  free (r);\n"
>         | RLenType -> pr "  rv = copy_type_len (len, t);\n"
> +       | RLenValue -> pr "  rv = copy_len (len);\n"

This call is wrong, and so is copy_len below.  What happens to 'r'?

>         | RLenTypeVal ->
>             pr "  rv = copy_type_value (r, len, t);\n";
>             pr "  free (r);\n"
> @@ -1983,6 +1998,18 @@ copy_type_len (size_t len, hive_type t)
>  }
>  
>  static value
> +copy_len (size_t len)
> +{
> +  CAMLparam0 ();
> +  CAMLlocal2 (v, rv);
> +
> +  rv = caml_alloc (1, 0);
> +  v = Val_int (len);
> +  Store_field (rv, 0, v);
> +  CAMLreturn (rv);
> +}

This creates a tuple with a single element, which OCaml can't actually
process.  In any case you need to be passing two parameters here: the
value and the len, and you need to make a 2-element tuple containing
both of them.

> +static value
>  copy_type_value (const char *r, size_t len, hive_type t)
>  {
>    CAMLparam0 ();
> @@ -2172,6 +2199,7 @@ sub open {
>  	 | RString
>  	 | RStringList
>  	 | RLenType
> +	 | RLenValue
>  	 | RLenTypeVal
>  	 | RInt32
>  	 | RInt64 -> ()
> @@ -2246,6 +2274,7 @@ and generate_perl_prototype name style =
>     | RString -> pr "$string = "
>     | RStringList -> pr "@strings = "
>     | RLenType -> pr "($type, $len) = "
> +   | RLenValue -> pr "($len) = "

Just a single length?  What about the value?

>     | RLenTypeVal -> pr "($type, $data) = "
>     | RInt32 -> pr "$int32 = "
>     | RInt64 -> pr "$int64 = "
> @@ -2469,6 +2498,7 @@ DESTROY (h)
>  	 | RValueList
>  	 | RStringList
>  	 | RLenType
> +	 | RLenValue
>  	 | RLenTypeVal -> pr "void\n"
>  	 | RInt32 -> pr "SV *\n"
>  	 | RInt64 -> pr "SV *\n"
> @@ -2641,6 +2671,20 @@ DESTROY (h)
>  	     pr "      PUSHs (sv_2mortal (newSViv (type)));\n";
>  	     pr "      PUSHs (sv_2mortal (newSViv (len)));\n";
>  
> +	 | RLenValue ->
> +	     pr "PREINIT:\n";
> +	     pr "      int r;\n";

int r?  The return from the function is a hive_value_h.

> +	     pr "      size_t len;\n";
> +	     pr " PPCODE:\n";
> +             pr "      r = hivex_%s (%s, &len);\n"
> +	       name (String.concat ", " c_params);
> +	     free_args ();
> +             pr "      if (r == 0)\n";
> +             pr "        croak (\"%%s: \", \"%s\", strerror (errno));\n"
> +	       name;
> +	     pr "      EXTEND (SP, 2);\n";
> +	     pr "      PUSHs (sv_2mortal (newSViv (len)));\n";

You extend the stack by two elements, then push one element.  This
would cause Perl to crash.  In any case you need to push both the
value (r) and the length.  I can't remember in which order you need to
push them -- take a look at other examples.

>  	 | RLenTypeVal ->
>  	     pr "PREINIT:\n";
>  	     pr "      char *r;\n";
> @@ -2879,6 +2923,14 @@ put_len_type (size_t len, hive_type t)
>  }
>  
>  static PyObject *
> +put_len (size_t len)
> +{
> +  PyObject *r = PyTuple_New (1);
> +  PyTuple_SetItem (r, 0, PyLong_FromLongLong ((long) len));
> +  return r;
> +}

Same problem in Python as in OCaml and Perl.

It's probably going to help if you make some small test programs in
all languages, so you can check the returned values are marshalled
properly.

> +static PyObject *
>  put_val_type (char *val, size_t len, hive_type t)
>  {
>    PyObject *r = PyTuple_New (2);
> @@ -2918,6 +2970,10 @@ put_val_type (char *val, size_t len, hive_type t)
>              pr "  size_t len;\n";
>              pr "  hive_type t;\n";
>              "-1"
> +        | RLenValue ->
> +            pr "  int r;\n";

As above.

> +            pr "  size_t len;\n";
> +            "0"
>          | RLenTypeVal ->
>              pr "  char *r;\n";
>              pr "  size_t len;\n";
> @@ -2942,6 +2998,7 @@ put_val_type (char *val, size_t len, hive_type t)
>        let c_params =
>          match fst style with
>          | RLenType | RLenTypeVal -> c_params @ ["&t"; "&len"]
> +        | RLenValue -> c_params @ ["&len"]
>          | _ -> c_params in
>  
>        List.iter (
> @@ -3086,6 +3143,8 @@ put_val_type (char *val, size_t len, hive_type t)
>             pr "  free_strings (r);\n"
>         | RLenType ->
>             pr "  py_r = put_len_type (len, t);\n"
> +       | RLenValue ->
> +           pr "  py_r = put_len (len);\n"

As above.

>         | RLenTypeVal ->
>             pr "  py_r = put_val_type (r, len, t);\n";
>             pr "  free (r);\n"
> @@ -3296,6 +3355,7 @@ get_values (VALUE valuesv, size_t *nr_values)
>            | RString -> "string"
>            | RStringList -> "list"
>            | RLenType -> "hash"
> +          | RLenValue -> "integer"
>            | RLenTypeVal -> "hash"
>            | RInt32 -> "integer"
>            | RInt64 -> "integer" in
> @@ -3394,6 +3454,10 @@ get_values (VALUE valuesv, size_t *nr_values)
>              pr "  size_t len;\n";
>              pr "  hive_type t;\n";
>              "-1"
> +        | RLenValue ->
> +            pr "  int r;\n";

As above (Ruby).

> +            pr "  size_t len;\n";
> +            "0"
>          | RLenTypeVal ->
>              pr "  char *r;\n";
>              pr "  size_t len;\n";
> @@ -3418,6 +3482,7 @@ get_values (VALUE valuesv, size_t *nr_values)
>        let c_params =
>          match ret with
>          | RLenType | RLenTypeVal -> c_params @ [["&t"; "&len"]]
> +        | RLenValue -> c_params @ [["&len"]]
>          | _ -> c_params in
>        let c_params = List.concat c_params in
>  
> @@ -3499,6 +3564,10 @@ get_values (VALUE valuesv, size_t *nr_values)
>          pr "  rb_hash_aset (rv, ID2SYM (rb_intern (\"len\")), INT2NUM (len));\n";
>          pr "  rb_hash_aset (rv, ID2SYM (rb_intern (\"type\")), INT2NUM (t));\n";
>          pr "  return rv;\n"
> +      | RLenValue ->
> +        pr "  VALUE rv = rb_hash_new ();\n";
> +        pr "  rb_hash_aset (rv, ID2SYM (rb_intern (\"len\")), INT2NUM (len));\n";
> +        pr "  return rv;\n"

As above.

>        | RLenTypeVal ->
>          pr "  VALUE rv = rb_hash_new ();\n";
>          pr "  rb_hash_aset (rv, ID2SYM (rb_intern (\"len\")), INT2NUM (len));\n";

Rich.

-- 
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