common safe write(2) wrapper

lib/libio.c

@@ -10,9 +10,22 @@ _strlen(char *s){
 	return i;
 }
 
+static int
+_write(int fd, char *s, int n){
+	int i;
+
+	for(
+		i = 0;
+		i < n;
+		i += write(fd, s+i, n-i)
+	);
+
+	return i;
+}
+
 int
 fdprint(int fd, char *s){
-	write(fd, s, _strlen(s));
+	return _write(fd, s, _strlen(s));
 }
 
 /* SLOW. DO NOT USE. */
@@ -45,7 +58,6 @@ fdputs(int fd, char *s){
 	int r;
 
 	i = _strlen(s);
-	r = 0;
 
 	/* RACE CONDITION */
 	/* This leaves s as an invalid string while the write(2) syscall is
@@ -53,11 +65,7 @@ fdputs(int fd, char *s){
 	 * implementation is unsuitable when s is shared between threads or
 	 * whatever the CS term for that is. */
 	s[i] = '\n';
-	for(
-		r = 0;
-		(r += write(fd, s, i + 1)) < i + 1;
-		s += r, i -= r
-	);
+	r = _write(fd, s, i + 1);
 	s[i] = '\0';
 
 	return r;