Add files via upload

src/util.c

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2022 Yubico AB. All rights reserved.
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file.
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "fido.h"
+
+int
+fido_to_uint64(const char *str, int base, uint64_t *out)
+{
+	char *ep;
+	unsigned long long ull;
+
+	errno = 0;
+	ull = strtoull(str, &ep, base);
+	if (str == ep || *ep != '\0')
+		return -1;
+	else if (ull == ULLONG_MAX && errno == ERANGE)
+		return -1;
+	else if (ull > UINT64_MAX)
+		return -1;
+	*out = (uint64_t)ull;
+
+	return 0;
+}