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	atnotify.c - 9base - revived minimalist port of Plan 9 userland to Unix
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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 }