/* SPDX-License-Identifier: GPL-2.0 */

  #ifndef _LINUX_NLS_H
  #define _LINUX_NLS_H
  
  #include <linux/init.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   * wchar_t values is now outdated.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;

  
  struct nls_table {

  	const char *charset;
  	const char *alias;

  	int (*uni2char) (wchar_t uni, unsigned char *out, int boundlen);
  	int (*char2uni) (const unsigned char *rawstring, int boundlen,
  			 wchar_t *uni);

  	const unsigned char *charset2lower;
  	const unsigned char *charset2upper;

  	struct module *owner;
  	struct nls_table *next;
  };
  
  /* 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 __register_nls(struct nls_table *, struct module *);

  extern int unregister_nls(struct nls_table *);
  extern struct nls_table *load_nls(char *);
  extern void unload_nls(struct nls_table *);
  extern struct nls_table *load_nls_default(void);

  #define register_nls(nls) __register_nls((nls), THIS_MODULE)

  extern int utf8_to_utf32(const u8 *s, int len, unicode_t *pu);
  extern int utf32_to_utf8(unicode_t u, u8 *s, int maxlen);

  extern int utf8s_to_utf16s(const u8 *s, int len,
  		enum utf16_endian endian, wchar_t *pwcs, int maxlen);

  extern int utf16s_to_utf8s(const wchar_t *pwcs, int len,
  		enum utf16_endian endian, u8 *s, int maxlen);

  
  static inline unsigned char nls_tolower(struct nls_table *t, unsigned char c)
  {
  	unsigned char nc = t->charset2lower[c];
  
  	return nc ? nc : c;
  }
  
  static inline unsigned char nls_toupper(struct nls_table *t, unsigned char c)
  {
  	unsigned char nc = t->charset2upper[c];
  
  	return nc ? nc : c;
  }
  
  static inline int nls_strnicmp(struct nls_table *t, const unsigned char *s1,
  		const unsigned char *s2, int len)
  {
  	while (len--) {
  		if (nls_tolower(t, *s1++) != nls_tolower(t, *s2++))
  			return 1;
  	}
  
  	return 0;
  }

  /*
   * nls_nullsize - return length of null character for codepage
   * @codepage - codepage for which to return length of NULL terminator
   *
   * Since we can't guarantee that the null terminator will be a particular
   * length, we have to check against the codepage. If there's a problem
   * determining it, assume a single-byte NULL terminator.
   */
  static inline int
  nls_nullsize(const struct nls_table *codepage)
  {
  	int charlen;
  	char tmp[NLS_MAX_CHARSET_SIZE];
  
  	charlen = codepage->uni2char(0, tmp, NLS_MAX_CHARSET_SIZE);
  
  	return charlen > 0 ? charlen : 1;
  }

  #define MODULE_ALIAS_NLS(name)	MODULE_ALIAS("nls_" __stringify(name))
  
  #endif /* _LINUX_NLS_H */