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12  * wchar_t values is now outdated.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 */
19 typedef u16 wchar_t;
20 #define MAX_WCHAR_T	0xffff
21 
22 /* Arbitrary Unicode character */
23 typedef u32 unicode_t;
24 
25 struct 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 */
41 enum utf16_endian {
42 	UTF16_HOST_ENDIAN,
43 	UTF16_LITTLE_ENDIAN,
44 	UTF16_BIG_ENDIAN
45 };
46 
47 /* nls_base.c */
48 extern int __register_nls(struct nls_table *, struct module *);
49 extern int unregister_nls(struct nls_table *);
50 extern struct nls_table *load_nls(const char *charset);
51 extern void unload_nls(struct nls_table *);
52 extern struct nls_table *load_nls_default(void);
53 #define register_nls(nls) __register_nls((nls), THIS_MODULE)
54 
55 extern int utf8_to_utf32(const u8 *s, int len, unicode_t *pu);
56 extern int utf32_to_utf8(unicode_t u, u8 *s, int maxlen);
57 extern int utf8s_to_utf16s(const u8 *s, int len,
58 		enum utf16_endian endian, wchar_t *pwcs, int maxlen);
59 extern int utf16s_to_utf8s(const wchar_t *pwcs, int len,
60 		enum utf16_endian endian, u8 *s, int maxlen);
61 
nls_tolower(struct nls_table * t,unsigned char c)62 static 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 
nls_toupper(struct nls_table * t,unsigned char c)69 static 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 
nls_strnicmp(struct nls_table * t,const unsigned char * s1,const unsigned char * s2,int len)76 static 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  */
95 static inline int
nls_nullsize(const struct nls_table * codepage)96 nls_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 
110