PipeWire  0.3.36
SPA Hooks

A SPA Hook is a data structure to keep track of callbacks. More...

Data Structures

struct  spa_hook_list
 A list of hooks. More...
 
struct  spa_hook
 A hook, contains the structure with functions and the data passed to the functions. More...
 

Macros

#define spa_hook_list_call_simple(l, type, method, vers, ...)
 
#define spa_hook_list_do_call(l, start, type, method, vers, once, ...)
 Call all hooks in a list, starting from the given one and optionally stopping after calling the first non-NULL function, returns the number of methods called. More...
 
#define spa_hook_list_call(l, t, m, v, ...)   spa_hook_list_do_call(l,NULL,t,m,v,false,##__VA_ARGS__)
 Call the method named m for each element in list l. More...
 
#define spa_hook_list_call_once(l, t, m, v, ...)   spa_hook_list_do_call(l,NULL,t,m,v,true,##__VA_ARGS__)
 Call the method named m for each element in list l, stopping after the first invocation. More...
 
#define spa_hook_list_call_start(l, s, t, m, v, ...)   spa_hook_list_do_call(l,s,t,m,v,false,##__VA_ARGS__)
 
#define spa_hook_list_call_once_start(l, s, t, m, v, ...)   spa_hook_list_do_call(l,s,t,m,v,true,##__VA_ARGS__)
 

Functions

void spa_hook_list_init (struct spa_hook_list *list)
 Initialize a hook list to the empty list. More...
 
bool spa_hook_list_is_empty (struct spa_hook_list *list)
 
void spa_hook_list_append (struct spa_hook_list *list, struct spa_hook *hook, const void *funcs, void *data)
 Append a hook. More...
 
void spa_hook_list_prepend (struct spa_hook_list *list, struct spa_hook *hook, const void *funcs, void *data)
 Prepend a hook. More...
 
void spa_hook_remove (struct spa_hook *hook)
 Remove a hook. More...
 
void spa_hook_list_clean (struct spa_hook_list *list)
 Remove all hooks from the list. More...
 
void spa_hook_list_isolate (struct spa_hook_list *list, struct spa_hook_list *save, struct spa_hook *hook, const void *funcs, void *data)
 
void spa_hook_list_join (struct spa_hook_list *list, struct spa_hook_list *save)
 

Detailed Description

A SPA Hook is a data structure to keep track of callbacks.

It is similar to the SPA Interfaces and typically used where an implementation allows for multiple external callback functions. For example, an implementation may use a hook list to implement signals with each caller using a hook to register callbacks to be invoked on those signals.

The below (pseudo)code is a minimal example outlining the use of hooks:

// the public interface
struct bar_events {
uint32_t version;
void (*boom)(void *data, const char *msg);
};
// private implementation
struct party {
struct spa_hook_list bar_list;
};
void party_add_event_listener(struct party *p, struct spa_hook *listener,
struct bar_events *events, void *data)
{
spa_hook_list_append(&p->bar_list, listener, events, data);
}
static void party_on(struct party *p)
{
spa_hook_list_call(&p->list, struct bar_events,
boom, // function name
0 // hardcoded version,
"party on, wayne");
}
#define spa_hook_list_call(l, t, m, v,...)
Call the method named m for each element in list l.
Definition: hook.h:407
void spa_hook_list_append(struct spa_hook_list *list, struct spa_hook *hook, const void *funcs, void *data)
Append a hook.
Definition: hook.h:316
user data to add to an object
Definition: filter.c:75
A list of hooks.
Definition: hook.h:284
A hook, contains the structure with functions and the data passed to the functions.
Definition: hook.h:295

In the caller, the hooks can be used like this:

static void boom_cb(void *data, const char *msg) {
// data is userdata from main()
printf("%s", msg);
}
static const struct bar_events {
.boom = boom_cb,
};
void main(void) {
void *userdata = whatever;
struct spa_hook hook;
struct party *p = start_the_party();
party_add_event_listener(p, &hook, boom_cb, userdata);
mainloop();
return 0;
}
int main(int argc, char *argv[])
Definition: media-session.c:2433

Macro Definition Documentation

◆ spa_hook_list_call

#define spa_hook_list_call (   l,
  t,
  m,
  v,
  ... 
)    spa_hook_list_do_call(l,NULL,t,m,v,false,##__VA_ARGS__)

Call the method named m for each element in list l.

t specifies the type of the callback struct.

◆ spa_hook_list_call_once

#define spa_hook_list_call_once (   l,
  t,
  m,
  v,
  ... 
)    spa_hook_list_do_call(l,NULL,t,m,v,true,##__VA_ARGS__)

Call the method named m for each element in list l, stopping after the first invocation.

t specifies the type of the callback struct.

◆ spa_hook_list_call_once_start

#define spa_hook_list_call_once_start (   l,
  s,
  t,
  m,
  v,
  ... 
)    spa_hook_list_do_call(l,s,t,m,v,true,##__VA_ARGS__)

◆ spa_hook_list_call_simple

#define spa_hook_list_call_simple (   l,
  type,
  method,
  vers,
  ... 
)
Value:
({ \
struct spa_hook_list *_l = l; \
struct spa_hook *_h, *_t; \
spa_list_for_each_safe(_h, _t, &_l->list, link) \
spa_callbacks_call(&_h->cb,type,method,vers, ## __VA_ARGS__); \
})

◆ spa_hook_list_call_start

#define spa_hook_list_call_start (   l,
  s,
  t,
  m,
  v,
  ... 
)    spa_hook_list_do_call(l,s,t,m,v,false,##__VA_ARGS__)

◆ spa_hook_list_do_call

#define spa_hook_list_do_call (   l,
  start,
  type,
  method,
  vers,
  once,
  ... 
)
Value:
({ \
struct spa_hook_list *list = l; \
struct spa_list *s = start ? (struct spa_list *)start : &list->list; \
struct spa_hook cursor = { 0 }, *ci; \
int count = 0; \
spa_list_cursor_start(cursor, s, link); \
spa_list_for_each_cursor(ci, cursor, &list->list, link) { \
const type *_f = (const type *)ci->cb.funcs; \
if (SPA_LIKELY(SPA_CALLBACK_CHECK(_f,method,vers))) { \
_f->method(ci->cb.data, ## __VA_ARGS__); \
count++; \
if (once) \
break; \
} \
} \
spa_list_cursor_end(cursor, link); \
count; \
})
#define SPA_CALLBACK_CHECK(c, m, v)
Check if a callback c has method m of version v.
Definition: hook.h:136
#define SPA_LIKELY(x)
Definition: defs.h:241
int(* start)(struct sm_media_session *sess)
Definition: media-session.c:2382
Definition: list.h:37

Call all hooks in a list, starting from the given one and optionally stopping after calling the first non-NULL function, returns the number of methods called.

Function Documentation

◆ spa_hook_list_append()

◆ spa_hook_list_clean()

◆ spa_hook_list_init()

◆ spa_hook_list_is_empty()

bool spa_hook_list_is_empty ( struct spa_hook_list list)
inline

◆ spa_hook_list_isolate()

void spa_hook_list_isolate ( struct spa_hook_list list,
struct spa_hook_list save,
struct spa_hook hook,
const void *  funcs,
void *  data 
)
inline

◆ spa_hook_list_join()

void spa_hook_list_join ( struct spa_hook_list list,
struct spa_hook_list save 
)
inline

◆ spa_hook_list_prepend()

void spa_hook_list_prepend ( struct spa_hook_list list,
struct spa_hook hook,
const void *  funcs,
void *  data 
)
inline

◆ spa_hook_remove()