1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef APR_OPTIONAL_H
18#define APR_OPTIONAL_H
19
20#include "apu.h"
21/**
22 * @file apr_optional.h
23 * @brief APR-UTIL registration of functions exported by modules
24 */
25#ifdef __cplusplus
26extern "C" {
27#endif
28
29/**
30 * @defgroup APR_Util_Opt Optional Functions
31 * @ingroup APR_Util
32 *
33 * Typesafe registration and retrieval of functions that may not be present
34 * (i.e. functions exported by optional modules)
35 * @{
36 */
37
38/**
39 * The type of an optional function.
40 * @param name The name of the function
41 */
42#define APR_OPTIONAL_FN_TYPE(name) apr_OFN_##name##_t
43
44/**
45 * Declare an optional function.
46 * @param ret The return type of the function
47 * @param name The name of the function
48 * @param args The function arguments (including brackets)
49 */
50#define APR_DECLARE_OPTIONAL_FN(ret,name,args) \
51typedef ret (APR_OPTIONAL_FN_TYPE(name)) args
52
53/**
54 * XXX: This doesn't belong here, then!
55 * Private function! DO NOT USE!
56 * @internal
57 */
58
59typedef void (apr_opt_fn_t)(void);
60/** @internal */
61APU_DECLARE_NONSTD(void) apr_dynamic_fn_register(const char *szName,
62                                                  apr_opt_fn_t *pfn);
63
64/**
65 * Register an optional function. This can be later retrieved, type-safely, by
66 * name. Like all global functions, the name must be unique. Note that,
67 * confusingly but correctly, the function itself can be static!
68 * @param name The name of the function
69 */
70#define APR_REGISTER_OPTIONAL_FN(name) do { \
71  APR_OPTIONAL_FN_TYPE(name) *apu__opt = name; \
72  apr_dynamic_fn_register(#name,(apr_opt_fn_t *)apu__opt); \
73} while (0)
74
75/** @internal
76 * Private function! DO NOT USE!
77 */
78APU_DECLARE(apr_opt_fn_t *) apr_dynamic_fn_retrieve(const char *szName);
79
80/**
81 * Retrieve an optional function. Returns NULL if the function is not present.
82 * @param name The name of the function
83 */
84#define APR_RETRIEVE_OPTIONAL_FN(name) \
85	(APR_OPTIONAL_FN_TYPE(name) *)apr_dynamic_fn_retrieve(#name)
86
87/** @} */
88#ifdef __cplusplus
89}
90#endif
91
92#endif /* APR_OPTIONAL_H */
93