Apache Portable Runtime
apr_optional.h
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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
26 extern "C" {
27 #endif
28 
29 /**
30  * @defgroup APR_Util_Opt Optional Functions
31  * @ingroup APR
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) \
51 typedef 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 
59 typedef void (apr_opt_fn_t)(void);
60 /** @internal */
61 APR_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  */
78 APR_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 */
void( apr_opt_fn_t)(void)
Definition: apr_optional.h:59
#define APR_DECLARE(type)
Definition: apr.h:500
#define APR_DECLARE_NONSTD(type)
Definition: apr.h:513