LXR linux/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  12 * wchar_t values is now outdated.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 */
  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(char *);
  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
 110