include/linux/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  12  * wchar_t values is now outdated.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 */
  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(char *);
  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
  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
  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
  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
  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