1 files changed, 58 insertions, 0 deletions
diff --git a/src/lib9/atnotify.c b/src/lib9/atnotify.c
new file mode 100644
index 00000000..60e8ad0c
--- /dev/null
+++ b/src/lib9/atnotify.c
@@ -0,0 +1,58 @@
+#include <u.h>
+#include <libc.h>
+
+#define	NFN	33
+static	int	(*onnot[NFN])(void*, char*);
+static	Lock	onnotlock;
+
+static
+void
+notifier(void *v, char *s)
+{
+	int i;
+
+	for(i=0; i<NFN; i++)
+		if(onnot[i] && ((*onnot[i])(v, s))){
+			noted(NCONT);
+			return;
+		}
+	noted(NDFLT);
+}
+
+int
+atnotify(int (*f)(void*, char*), int in)
+{
+	int i, n, ret;
+	static int init;
+
+	if(!init){
+		notify(notifier);
+		init = 1;		/* assign = */
+	}
+	ret = 0;
+	lock(&onnotlock);
+	if(in){
+		for(i=0; i<NFN; i++)
+			if(onnot[i] == 0) {
+				onnot[i] = f;
+				ret = 1;
+				break;
+			}
+	}else{
+		n = 0;
+		for(i=0; i<NFN; i++)
+			if(onnot[i]){
+				if(ret==0 && onnot[i]==f){
+					onnot[i] = 0;
+					ret = 1;
+				}else
+					n++;
+			}
+		if(n == 0){
+			init = 0;
+			notify(0);
+		}
+	}
+	unlock(&onnotlock);
+	return ret;
+}