Factor out readrune and writerune

libutf/writerune.c

@@ -0,0 +1,23 @@
+/* See LICENSE file for copyright and license details. */
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "../utf.h"
+
+void
+writerune(Rune *r)
+{
+	char buf[UTFmax];
+	int n;
+
+	if ((n = runetochar(buf, r)) > 0) {
+		fwrite(buf, n, 1, stdout);
+		if (ferror(stdout)) {
+			fprintf(stderr, "stdout: write error: %s\n",
+				strerror(errno));
+			exit(1);
+		}
+	}
+}