lib: Port basic Linux kernel NLS functions

Port basic Linux kernel NLS functions: utf8_to_utf32() and
utf8s_to_utf16s() in order to support porting kernel code that uses
them.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 40 insertions, 0 deletions

diff --git a/include/linux/nls.h b/include/linux/nls.h
new file mode 100644
index 0000000000..62fb7b5a97
--- /dev/null
+++ b/include/linux/nls.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_NLS_H
+#define _LINUX_NLS_H
+
+/* Unicode has changed over the years.  Unicode code points no longer
+ * fit into 16 bits; as of Unicode 5 valid code points range from 0
+ * to 0x10ffff (17 planes, where each plane holds 65536 code points).
+ *
+ * The original decision to represent Unicode characters as 16-bit
+ * wchar_t values is now outdated.  But plane 0 still includes the
+ * most commonly used characters, so we will retain it.  The newer
+ * 32-bit unicode_t type can be used when it is necessary to
+ * represent the full Unicode character set.
+ */
+
+/* Plane-0 Unicode character */
+typedef u16 wchar_t;
+#define MAX_WCHAR_T	0xffff
+
+/* Arbitrary Unicode character */
+typedef u32 unicode_t;
+
+/* this value hold the maximum octet of charset */
+#define NLS_MAX_CHARSET_SIZE 6 /* for UTF-8 */
+
+/* Byte order for UTF-16 strings */
+enum utf16_endian {
+	UTF16_HOST_ENDIAN,
+	UTF16_LITTLE_ENDIAN,
+	UTF16_BIG_ENDIAN
+};
+
+/* nls_base.c */
+
+extern int utf8_to_utf32(const u8 *s, int len, unicode_t *pu);
+extern int utf8s_to_utf16s(const u8 *s, int len,
+		enum utf16_endian endian, wchar_t *pwcs, int maxlen);
+
+#endif /* _LINUX_NLS_H */
+