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git.proxmox.com Git - mirror_frr.git/blob - lib/hook.h
2 * Copyright (c) 2016 David Lamparter, for NetDEF, Inc.
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31 /* type-safe subscribable hook points
33 * where "type-safe" applies to the function pointers used for subscriptions
40 * DECLARE_HOOK (some_update_event, (struct eventinfo *info), (info))
43 * DEFINE_HOOK (some_update_event, (struct eventinfo *info), (info))
45 * hook_call (some_update_event, info)
47 * Note: the second and third macro args must be the hook function's
48 * parameter list, with the same names for each parameter. The second
49 * macro arg is with types (used for defining things), the third arg is
50 * just the names (used for passing along parameters).
52 * Do not use parameter names starting with "hook", these can collide with
53 * names used by the hook code itself.
55 * The return value is always "int" for now; hook_call will sum up the
56 * return values from each registered user. Default is 0.
58 * There are no pre-defined semantics for the value, in most cases it is
59 * ignored. For success/failure indication, 0 should be success, and
60 * handlers should make sure to only return 0 or 1 (not -1 or other values).
63 * - to use a hook / create a handler:
65 * #include "mydaemon.h"
66 * int event_handler (struct eventinfo *info) { ... }
67 * hook_register (some_update_event, event_handler);
69 * or, if you need an argument to be passed along (addonptr will be added
70 * as first argument when calling the handler):
72 * #include "mydaemon.h"
73 * int event_handler (void *addonptr, struct eventinfo *info) { ... }
74 * hook_register_arg (some_update_event, event_handler, addonptr);
76 * (addonptr isn't typesafe, but that should be manageable.)
80 * - hook_unregister_all_module()
81 * - introspection / CLI / debug
84 * For loadable modules, the idea is that hooks could be automatically
85 * unregistered when a module is unloaded.
87 * It's also possible to add a constructor (MTYPE style) to DEFINE_HOOK,
88 * which would make it possible for the CLI to show all hooks and all
89 * registered handlers.
94 void *hookfn
; /* actually a function pointer */
97 struct frrmod_runtime
*module
;
103 struct hookent
*entries
;
106 /* subscribe/add callback function to a hook
108 * always use hook_register(), which uses the static inline helper from
109 * DECLARE_HOOK in order to get type safety
111 extern void _hook_register(struct hook
*hook
, void *funcptr
, void *arg
,
112 bool has_arg
, struct frrmod_runtime
*module
,
113 const char *funcname
);
114 #define hook_register(hookname, func) \
115 _hook_register(&_hook_ ## hookname, \
116 _hook_typecheck_ ## hookname (func), \
117 NULL, false, THIS_MODULE, #func)
118 #define hook_register_arg(hookname, func, arg) \
119 _hook_register(&_hook_ ## hookname, \
120 _hook_typecheck_arg_ ## hookname (func), \
121 arg, true, THIS_MODULE, #func)
123 extern void _hook_unregister(struct hook
*hook
, void *funcptr
, void *arg
,
125 #define hook_unregister(hookname, func) \
126 _hook_unregister(&_hook_ ## hookname, \
127 _hook_typecheck_ ## hookname (func), NULL, false)
128 #define hook_unregister_arg(hookname, func, arg) \
129 _hook_unregister(&_hook_ ## hookname, \
130 _hook_typecheck_arg_ ## hookname (func), arg, true)
133 * this is private (static) to the file that has the DEFINE_HOOK statement
135 #define hook_call(hookname, ...) \
136 hook_call_ ## hookname (__VA_ARGS__)
138 /* helpers to add the void * arg */
139 #define HOOK_ADDDEF(...) (void *hookarg , ## __VA_ARGS__)
140 #define HOOK_ADDARG(...) (hookarg , ## __VA_ARGS__)
142 /* use in header file - declares the hook and its arguments
143 * usage: DECLARE_HOOK(my_hook, (int arg1, struct foo *arg2), (arg1, arg2))
144 * as above, "passlist" must use the same order and same names as "arglist"
146 * theoretically passlist is not neccessary, but let's keep things simple and
147 * use exact same args on DECLARE and DEFINE.
149 #define DECLARE_HOOK(hookname, arglist, passlist) \
150 extern struct hook _hook_ ## hookname; \
151 __attribute__((unused)) \
152 static void *_hook_typecheck_ ## hookname ( \
153 int (*funcptr) arglist) { \
154 return (void *)funcptr; } \
155 __attribute__((unused)) \
156 static void *_hook_typecheck_arg_ ## hookname ( \
157 int (*funcptr) HOOK_ADDDEF arglist) { \
158 return (void *)funcptr; }
160 /* use in source file - contains hook-related definitions.
162 #define DEFINE_HOOK(hookname, arglist, passlist) \
163 struct hook _hook_ ## hookname = { \
167 static int hook_call_ ## hookname arglist { \
169 struct hookent *he = _hook_ ## hookname .entries; \
173 int (*fptr) arglist; \
174 int (*farg) HOOK_ADDDEF arglist; \
176 for (; he; he = he->next) { \
177 hookarg = he->hookarg; \
178 hookp.voidptr = he->hookfn; \
180 hooksum += hookp.fptr passlist; \
182 hooksum += hookp.farg HOOK_ADDARG passlist; \
187 #endif /* _FRR_HOOK_H */