1 files changed, 89 insertions, 0 deletions
diff --git a/lib/isc/utf8.c b/lib/isc/utf8.c
new file mode 100644
index 0000000..a348c5d
--- /dev/null
+++ b/lib/isc/utf8.c
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#include <string.h>
+
+#include <isc/utf8.h>
+#include <isc/util.h>
+
+/*
+ * UTF-8 is defined in "The Unicode Standard -- Version 4.0"
+ * Also see RFC 3629.
+ *
+ * Char. number range  |        UTF-8 octet sequence
+ *    (hexadecimal)    |              (binary)
+ *  --------------------+---------------------------------------------
+ * 0000 0000-0000 007F | 0xxxxxxx
+ * 0000 0080-0000 07FF | 110xxxxx 10xxxxxx
+ * 0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
+ * 0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+ */
+bool
+isc_utf8_valid(const unsigned char *buf, size_t len) {
+	REQUIRE(buf != NULL);
+
+	for (size_t i = 0; i < len; i++) {
+		if (buf[i] <= 0x7f) {
+			continue;
+		}
+		if ((i + 1) < len && (buf[i] & 0xe0) == 0xc0 &&
+		    (buf[i + 1] & 0xc0) == 0x80)
+		{
+			unsigned int w;
+			w = (buf[i] & 0x1f) << 6;
+			w |= (buf[++i] & 0x3f);
+			if (w < 0x80) {
+				return (false);
+			}
+			continue;
+		}
+		if ((i + 2) < len && (buf[i] & 0xf0) == 0xe0 &&
+		    (buf[i + 1] & 0xc0) == 0x80 && (buf[i + 2] & 0xc0) == 0x80)
+		{
+			unsigned int w;
+			w = (buf[i] & 0x0f) << 12;
+			w |= (buf[++i] & 0x3f) << 6;
+			w |= (buf[++i] & 0x3f);
+			if (w < 0x0800) {
+				return (false);
+			}
+			continue;
+		}
+		if ((i + 3) < len && (buf[i] & 0xf8) == 0xf0 &&
+		    (buf[i + 1] & 0xc0) == 0x80 &&
+		    (buf[i + 2] & 0xc0) == 0x80 && (buf[i + 3] & 0xc0) == 0x80)
+		{
+			unsigned int w;
+			w = (buf[i] & 0x07) << 18;
+			w |= (buf[++i] & 0x3f) << 12;
+			w |= (buf[++i] & 0x3f) << 6;
+			w |= (buf[++i] & 0x3f);
+			if (w < 0x10000 || w > 0x10FFFF) {
+				return (false);
+			}
+			continue;
+		}
+		return (false);
+	}
+	return (true);
+}
+
+bool
+isc_utf8_bom(const unsigned char *buf, size_t len) {
+	REQUIRE(buf != NULL);
+
+	if (len >= 3U && !memcmp(buf, "\xef\xbb\xbf", 3)) {
+		return (true);
+	}
+	return (false);
+}