--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libutil/hexstdin.c	Sun Feb 21 19:08:14 2021 +0000
@@ -0,0 +1,42 @@
+/*
+ * This module contains the function for reading hex data from stdin.
+ */
+
+#include <sys/types.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+read_hex_from_stdin(databuf, maxlen)
+	u_char *databuf;
+	unsigned maxlen;
+{
+	unsigned count;
+	int c, c2;
+
+	for (count = 0; ; count++) {
+		do
+			c = getchar();
+		while (isspace(c));
+		if (c < 0)
+			break;
+		if (!isxdigit(c)) {
+inv_input:		fprintf(stderr, "error: invalid hex input on stdin\n");
+			return(-1);
+		}
+		c2 = getchar();
+		if (!isxdigit(c2))
+			goto inv_input;
+		if (count >= maxlen) {
+			fprintf(stderr, "error: stdin hex data is too long\n");
+			return(-1);
+		}
+		databuf[count] = (decode_hex_digit(c) << 4) |
+				 decode_hex_digit(c2);
+	}
+	if (!count) {
+		fprintf(stderr, "error: no hex data given on stdin\n");
+		return(-1);
+	}
+	return(count);
+}