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libguestfs/generator/erlang.ml
Richard W.M. Jones fd9ac7f47d generator: Implement Pointer arguments. 
This implements Pointer arguments properly, at least for certain
limited definitions of "implements" and "properly".

'Pointer' as an argument type is meant to indicate a pointer passed to
an API.  The canonical example is the following proposed API:

  int guestfs_add_libvirt_dom (guestfs_h *g, virDomainPtr dom, ...);

where 'dom' is described in the generator as:

  Pointer ("virDomainPtr", "dom")

Pointer existed already in the generator, but the implementation was
broken.  It is not used by any existing API.

There are two basic difficulties of implementing Pointer:

(1) In language bindings there is no portable way to turn (eg.) a Perl
Sys::Virt 'dom' object into a C virDomainPtr.

(2) We can't rely on <libvirt/libvirt.h> being included (since it's an
optional dependency).

In this commit, we solve (2) by using a 'void *'.

We don't solve (1), really.  Instead we have a macro
POINTER_NOT_IMPLEMENTED which is used by currently all the non-C
language bindings.  It complains loudly and passes a NULL to the
underlying function.  The underlying function detects the NULL and
safely returns an error.  It is to be hoped that people will
contribute patches to make each language binding work, although in
some bindings it will always remain impossible to implement.
2014-12-11 14:15:00 +00:00

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(* libguestfs
* Copyright (C) 2011 Red Hat Inc.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*)
(* Please read generator/README first. *)
open Printf
open Types
open Utils
open Pr
open Docstrings
open Optgroups
open Actions
open Structs
open C
open Events
let rec generate_erlang_erl () =
generate_header ErlangStyle LGPLv2plus;
pr "-module(guestfs).\n";
pr "\n";
pr "-export([create/0, create/1, close/1, init/1]).\n";
pr "\n";
(* Export the public actions. *)
List.iter (
fun { name = name; style = _, args, optargs; non_c_aliases = aliases } ->
let nr_args = List.length args in
let export name =
if optargs = [] then
pr "-export([%s/%d]).\n" name (nr_args+1)
else
pr "-export([%s/%d, %s/%d]).\n" name (nr_args+1) name (nr_args+2)
in
export name;
List.iter export aliases
) external_functions_sorted;
pr "\n";
pr "\
create() ->
create(\"erl-guestfs\").
create(ExtProg) ->
G = spawn(?MODULE, init, [ExtProg]),
{ok, G}.
close(G) ->
G ! close,
ok.
call_port(G, Args) ->
G ! {call, self(), Args},
receive
{guestfs, Result} ->
Result
end.
init(ExtProg) ->
process_flag(trap_exit, true),
Port = open_port({spawn, ExtProg}, [{packet, 4}, binary]),
loop(Port).
loop(Port) ->
receive
{call, Caller, Args} ->
Port ! { self(), {command, term_to_binary(Args)}},
receive
{Port, {data, Result}} ->
Caller ! { guestfs, binary_to_term(Result)}
end,
loop(Port);
close ->
port_close(Port),
exit(normal);
{ 'EXIT', Port, _ } ->
exit(port_terminated)
end.
";
(* These bindings just marshal the parameters and call the back-end
* process which dispatches them to the port.
*)
List.iter (
fun { name = name; style = _, args, optargs; non_c_aliases = aliases } ->
pr "%s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr ") ->\n";
pr " call_port(G, {%s" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr "}).\n";
(* For functions with optional arguments, make a variant that
* has no optarg array, which just calls the function above with
* an empty list as the final arg.
*)
if optargs <> [] then (
pr "%s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ") ->\n";
pr " %s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ", []";
pr ").\n"
);
(* Aliases. *)
List.iter (
fun alias ->
pr "%s(G" alias;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr ") ->\n";
pr " %s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr ").\n";
if optargs <> [] then (
pr "%s(G" alias;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ") ->\n";
pr " %s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ").\n"
)
) aliases;
pr "\n"
) external_functions_sorted
and generate_erlang_c () =
generate_header CStyle GPLv2plus;
pr "\
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <erl_interface.h>
/* We should switch over to using
#include <ei.h>
instead of erl_interface.
*/
#include \"guestfs.h\"
#include \"guestfs-internal-frontend.h\"
extern guestfs_h *g;
extern ETERM *dispatch (ETERM *message);
extern int atom_equals (ETERM *atom, const char *name);
extern ETERM *make_error (const char *funname);
extern ETERM *unknown_optarg (const char *funname, ETERM *optargname);
extern ETERM *unknown_function (ETERM *fun);
extern ETERM *make_string_list (char **r);
extern ETERM *make_table (char **r);
extern ETERM *make_bool (int r);
extern char **get_string_list (ETERM *term);
extern int get_bool (ETERM *term);
extern int get_int (ETERM *term);
extern int64_t get_int64 (ETERM *term);
#define ARG(i) (ERL_TUPLE_ELEMENT(message,(i)+1))
";
(* Struct copy functions. *)
let emit_copy_list_function typ =
pr "static ETERM *\n";
pr "make_%s_list (const struct guestfs_%s_list *%ss)\n" typ typ typ;
pr "{\n";
pr " ETERM *t[%ss->len];\n" typ;
pr " size_t i;\n";
pr "\n";
pr " for (i = 0; i < %ss->len; ++i)\n" typ;
pr " t[i] = make_%s (&%ss->val[i]);\n" typ typ;
pr "\n";
pr " return erl_mk_list (t, %ss->len);\n" typ;
pr "}\n";
pr "\n";
in
List.iter (
fun { s_name = typ; s_cols = cols } ->
pr "static ETERM *\n";
pr "make_%s (const struct guestfs_%s *%s)\n" typ typ typ;
pr "{\n";
pr " ETERM *t[%d];\n" (List.length cols);
pr "\n";
iteri (
fun i col ->
(match col with
| name, FString ->
pr " t[%d] = erl_mk_string (%s->%s);\n" i typ name
| name, FBuffer ->
pr " t[%d] = erl_mk_estring (%s->%s, %s->%s_len);\n"
i typ name typ name
| name, FUUID ->
pr " t[%d] = erl_mk_estring (%s->%s, 32);\n" i typ name
| name, (FBytes|FInt64|FUInt64) ->
pr " t[%d] = erl_mk_longlong (%s->%s);\n" i typ name
| name, (FInt32|FUInt32) ->
pr " t[%d] = erl_mk_int (%s->%s);\n" i typ name
| name, FOptPercent ->
pr " if (%s->%s >= 0)\n" typ name;
pr " t[%d] = erl_mk_float (%s->%s);\n" i typ name;
pr " else\n";
pr " t[%d] = erl_mk_atom (\"undefined\");\n" i;
| name, FChar ->
pr " t[%d] = erl_mk_int (%s->%s);\n" i typ name
);
) cols;
pr "\n";
pr " return erl_mk_list (t, %d);\n" (List.length cols);
pr "}\n";
pr "\n";
) external_structs;
(* Emit a copy_TYPE_list function definition only if that function is used. *)
List.iter (
function
| typ, (RStructListOnly | RStructAndList) ->
(* generate the function for typ *)
emit_copy_list_function typ
| typ, _ -> () (* empty *)
) (rstructs_used_by external_functions);
(* The wrapper functions. *)
List.iter (
fun { name = name; style = (ret, args, optargs as style);
c_function = c_function; c_optarg_prefix = c_optarg_prefix } ->
pr "static ETERM *\n";
pr "run_%s (ETERM *message)\n" name;
pr "{\n";
iteri (
fun i ->
function
| Pathname n
| Device n | Mountable n | Dev_or_Path n | Mountable_or_Path n
| String n
| FileIn n
| FileOut n
| Key n
| GUID n ->
pr " CLEANUP_FREE char *%s = erl_iolist_to_string (ARG (%d));\n" n i
| OptString n ->
pr " CLEANUP_FREE char *%s;\n" n;
pr " if (atom_equals (ARG (%d), \"undefined\"))\n" i;
pr " %s = NULL;\n" n;
pr " else\n";
pr " %s = erl_iolist_to_string (ARG (%d));\n" n i
| BufferIn n ->
pr " ETERM *%s_bin = erl_iolist_to_binary (ARG (%d));\n" n i;
pr " const void *%s = ERL_BIN_PTR (%s_bin);\n" n n;
pr " size_t %s_size = ERL_BIN_SIZE (%s_bin);\n" n n
| StringList n | DeviceList n ->
pr " CLEANUP_FREE_STRING_LIST char **%s = get_string_list (ARG (%d));\n" n i
| Bool n ->
pr " int %s = get_bool (ARG (%d));\n" n i
| Int n ->
pr " int %s = get_int (ARG (%d));\n" n i
| Int64 n ->
pr " int64_t %s = get_int64 (ARG (%d));\n" n i
| Pointer (t, n) ->
pr " void * /* %s */ %s = POINTER_NOT_IMPLEMENTED (\"%s\");\n" t n t
) args;
(* Optional arguments. *)
if optargs <> [] then (
pr "\n";
pr " struct %s optargs_s = { .bitmask = 0 };\n" c_function;
pr " struct %s *optargs = &optargs_s;\n" c_function;
pr " ETERM *optargst = ARG (%d);\n" (List.length args);
pr " while (!ERL_IS_EMPTY_LIST (optargst)) {\n";
pr " ETERM *hd = ERL_CONS_HEAD (optargst);\n";
pr " ETERM *hd_name = ERL_TUPLE_ELEMENT (hd, 0);\n";
pr " ETERM *hd_value = ERL_TUPLE_ELEMENT (hd, 1);\n";
pr "\n";
List.iter (
fun argt ->
let n = name_of_optargt argt in
let uc_n = String.uppercase n in
pr " if (atom_equals (hd_name, \"%s\")) {\n" n;
pr " optargs_s.bitmask |= %s_%s_BITMASK;\n"
c_optarg_prefix uc_n;
pr " optargs_s.%s = " n;
(match argt with
| OBool _ -> pr "get_bool (hd_value)"
| OInt _ -> pr "get_int (hd_value)"
| OInt64 _ -> pr "get_int64 (hd_value)"
| OString _ -> pr "erl_iolist_to_string (hd_value)"
| OStringList n -> pr "get_string_list (hd_value)"
);
pr ";\n";
pr " }\n";
pr " else\n";
) optargs;
pr " return unknown_optarg (\"%s\", hd_name);\n" name;
pr " optargst = ERL_CONS_TAIL (optargst);\n";
pr " }\n";
pr "\n";
);
(match ret with
| RErr -> pr " int r;\n"
| RInt _ -> pr " int r;\n"
| RInt64 _ -> pr " int64_t r;\n"
| RBool _ -> pr " int r;\n"
| RConstString _ | RConstOptString _ ->
pr " const char *r;\n"
| RString _ -> pr " char *r;\n"
| RStringList _ ->
pr " char **r;\n"
| RStruct (_, typ) ->
pr " struct guestfs_%s *r;\n" typ
| RStructList (_, typ) ->
pr " struct guestfs_%s_list *r;\n" typ
| RHashtable _ ->
pr " char **r;\n"
| RBufferOut _ ->
pr " char *r;\n";
pr " size_t size;\n"
);
pr "\n";
pr " r = %s " c_function;
generate_c_call_args ~handle:"g" style;
pr ";\n";
(* Free strings if we copied them above. *)
List.iter (
function
| OBool _ | OInt _ | OInt64 _ -> ()
| OString n ->
let uc_n = String.uppercase n in
pr " if ((optargs_s.bitmask & %s_%s_BITMASK))\n"
c_optarg_prefix uc_n;
pr " free ((char *) optargs_s.%s);\n" n
| OStringList n ->
let uc_n = String.uppercase n in
pr " if ((optargs_s.bitmask & %s_%s_BITMASK))\n"
c_optarg_prefix uc_n;
pr " guestfs___free_string_list ((char **) optargs_s.%s);\n" n
) optargs;
(match errcode_of_ret ret with
| `CannotReturnError -> ()
| `ErrorIsMinusOne ->
pr " if (r == -1)\n";
pr " return make_error (\"%s\");\n" name;
| `ErrorIsNULL ->
pr " if (r == NULL)\n";
pr " return make_error (\"%s\");\n" name;
);
pr "\n";
(match ret with
| RErr -> pr " return erl_mk_atom (\"ok\");\n"
| RInt _ -> pr " return erl_mk_int (r);\n"
| RInt64 _ -> pr " return erl_mk_longlong (r);\n"
| RBool _ -> pr " return make_bool (r);\n"
| RConstString _ -> pr " return erl_mk_string (r);\n"
| RConstOptString _ ->
pr " ETERM *rt;\n";
pr " if (r)\n";
pr " rt = erl_mk_string (r);\n";
pr " else\n";
pr " rt = erl_mk_atom (\"undefined\");\n";
pr " return rt;\n"
| RString _ ->
pr " ETERM *rt = erl_mk_string (r);\n";
pr " free (r);\n";
pr " return rt;\n"
| RStringList _ ->
pr " ETERM *rt = make_string_list (r);\n";
pr " guestfs___free_string_list (r);\n\n";
pr " return rt;\n"
| RStruct (_, typ) ->
pr " ETERM *rt = make_%s (r);\n" typ;
pr " guestfs_free_%s (r);\n" typ;
pr " return rt;\n"
| RStructList (_, typ) ->
pr " ETERM *rt = make_%s_list (r);\n" typ;
pr " guestfs_free_%s_list (r);\n" typ;
pr " return rt;\n"
| RHashtable _ ->
pr " ETERM *rt = make_table (r);\n";
pr " guestfs___free_string_list (r);\n";
pr " return rt;\n"
| RBufferOut _ ->
pr " ETERM *rt = erl_mk_estring (r, size);\n";
pr " free (r);\n";
pr " return rt;\n"
);
pr "}\n";
pr "\n";
) external_functions_sorted;
pr "\
ETERM *
dispatch (ETERM *message)
{
ETERM *fun;
fun = ERL_TUPLE_ELEMENT (message, 0);
/* XXX We should use gperf here. */
";
List.iter (
fun { name = name; style = ret, args, optargs } ->
pr "if (atom_equals (fun, \"%s\"))\n" name;
pr " return run_%s (message);\n" name;
pr " else ";
) external_functions_sorted;
pr "return unknown_function (fun);
}
";
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