9base

revived minimalist port of Plan 9 userland to Unix
git clone git://git.suckless.org/9base
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atnotify.c (780B)

      1 #include <u.h>
      2 #include <libc.h>
      3 
      4 #define	NFN	33
      5 static	int	(*onnot[NFN])(void*, char*);
      6 static	Lock	onnotlock;
      7 
      8 static
      9 void
     10 notifier(void *v, char *s)
     11 {
     12 	int i;
     13 
     14 	for(i=0; i<NFN; i++)
     15 		if(onnot[i] && ((*onnot[i])(v, s))){
     16 			noted(NCONT);
     17 			return;
     18 		}
     19 	noted(NDFLT);
     20 }
     21 
     22 int
     23 atnotify(int (*f)(void*, char*), int in)
     24 {
     25 	int i, n, ret;
     26 	static int init;
     27 
     28 	if(!init){
     29 		notify(notifier);
     30 		init = 1;		/* assign = */
     31 	}
     32 	ret = 0;
     33 	lock(&onnotlock);
     34 	if(in){
     35 		for(i=0; i<NFN; i++)
     36 			if(onnot[i] == 0) {
     37 				onnot[i] = f;
     38 				ret = 1;
     39 				break;
     40 			}
     41 	}else{
     42 		n = 0;
     43 		for(i=0; i<NFN; i++)
     44 			if(onnot[i]){
     45 				if(ret==0 && onnot[i]==f){
     46 					onnot[i] = 0;
     47 					ret = 1;
     48 				}else
     49 					n++;
     50 			}
     51 		if(n == 0){
     52 			init = 0;
     53 			notify(0);
     54 		}
     55 	}
     56 	unlock(&onnotlock);
     57 	return ret;
     58 }