nls.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_NLS_H
  3#define _LINUX_NLS_H
  4
  5#include <linux/init.h>
  6
  7/* Unicode has changed over the years.  Unicode code points no longer
  8 * fit into 16 bits; as of Unicode 5 valid code points range from 0
  9 * to 0x10ffff (17 planes, where each plane holds 65536 code points).
 10 *
 11 * The original decision to represent Unicode characters as 16-bit
 12 * wchar_t values is now outdated.  But plane 0 still includes the
 13 * most commonly used characters, so we will retain it.  The newer
 14 * 32-bit unicode_t type can be used when it is necessary to
 15 * represent the full Unicode character set.
 16 */
 17
 18/* Plane-0 Unicode character */
 19typedef u16 wchar_t;
 20#define MAX_WCHAR_T	0xffff
 21
 22/* Arbitrary Unicode character */
 23typedef u32 unicode_t;
 24
 25struct nls_table {
 26	const char *charset;
 27	const char *alias;
 28	int (*uni2char) (wchar_t uni, unsigned char *out, int boundlen);
 29	int (*char2uni) (const unsigned char *rawstring, int boundlen,
 30			 wchar_t *uni);
 31	const unsigned char *charset2lower;
 32	const unsigned char *charset2upper;
 33	struct module *owner;
 34	struct nls_table *next;
 35};
 36
 37/* this value hold the maximum octet of charset */
 38#define NLS_MAX_CHARSET_SIZE 6 /* for UTF-8 */
 39
 40/* Byte order for UTF-16 strings */
 41enum utf16_endian {
 42	UTF16_HOST_ENDIAN,
 43	UTF16_LITTLE_ENDIAN,
 44	UTF16_BIG_ENDIAN
 45};
 46
 47/* nls_base.c */
 48extern int __register_nls(struct nls_table *, struct module *);
 49extern int unregister_nls(struct nls_table *);
 50extern struct nls_table *load_nls(const char *charset);
 51extern void unload_nls(struct nls_table *);
 52extern struct nls_table *load_nls_default(void);
 53#define register_nls(nls) __register_nls((nls), THIS_MODULE)
 54
 55extern int utf8_to_utf32(const u8 *s, int len, unicode_t *pu);
 56extern int utf32_to_utf8(unicode_t u, u8 *s, int maxlen);
 57extern int utf8s_to_utf16s(const u8 *s, int len,
 58		enum utf16_endian endian, wchar_t *pwcs, int maxlen);
 59extern int utf16s_to_utf8s(const wchar_t *pwcs, int len,
 60		enum utf16_endian endian, u8 *s, int maxlen);
 61
 62static inline unsigned char nls_tolower(struct nls_table *t, unsigned char c)
 63{
 64	unsigned char nc = t->charset2lower[c];
 65
 66	return nc ? nc : c;
 67}
 68
 69static inline unsigned char nls_toupper(struct nls_table *t, unsigned char c)
 70{
 71	unsigned char nc = t->charset2upper[c];
 72
 73	return nc ? nc : c;
 74}
 75
 76static inline int nls_strnicmp(struct nls_table *t, const unsigned char *s1,
 77		const unsigned char *s2, int len)
 78{
 79	while (len--) {
 80		if (nls_tolower(t, *s1++) != nls_tolower(t, *s2++))
 81			return 1;
 82	}
 83
 84	return 0;
 85}
 86
 87/*
 88 * nls_nullsize - return length of null character for codepage
 89 * @codepage - codepage for which to return length of NULL terminator
 90 *
 91 * Since we can't guarantee that the null terminator will be a particular
 92 * length, we have to check against the codepage. If there's a problem
 93 * determining it, assume a single-byte NULL terminator.
 94 */
 95static inline int
 96nls_nullsize(const struct nls_table *codepage)
 97{
 98	int charlen;
 99	char tmp[NLS_MAX_CHARSET_SIZE];
100
101	charlen = codepage->uni2char(0, tmp, NLS_MAX_CHARSET_SIZE);
102
103	return charlen > 0 ? charlen : 1;
104}
105
106#define MODULE_ALIAS_NLS(name)	MODULE_ALIAS("nls_" __stringify(name))
107
108#endif /* _LINUX_NLS_H */
109