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

  /*
   *  charset conversion utils
   *
   *  Copyright (c) 2017 Rob Clark

   */
  
  #ifndef __CHARSET_H_
  #define __CHARSET_H_

  #include <linux/kernel.h>

  #include <linux/types.h>

  #define MAX_UTF8_PER_UTF16 3

  
  /**

   * console_read_unicode() - read Unicode code point from console
   *
   * @code:	pointer to store Unicode code point
   * Return:	0 = success
   */
  int console_read_unicode(s32 *code);
  
  /**

   * utf8_get() - get next UTF-8 code point from buffer
   *
   * @src:		pointer to current byte, updated to point to next byte
   * Return:		code point, or 0 for end of string, or -1 if no legal
   *			code point is found. In case of an error src points to
   *			the incorrect byte.
   */
  s32 utf8_get(const char **src);
  
  /**
   * utf8_put() - write UTF-8 code point to buffer
   *
   * @code:		code point
   * @dst:		pointer to destination buffer, updated to next position
   * Return:		-1 if the input parameters are invalid
   */
  int utf8_put(s32 code, char **dst);
  
  /**
   * utf8_utf16_strnlen() - length of a truncated utf-8 string after conversion
   *			  to utf-16
   *
   * @src:		utf-8 string
   * @count:		maximum number of code points to convert
   * Return:		length in bytes after conversion to utf-16 without the
   *			trailing \0. If an invalid UTF-8 sequence is hit one
   *			word will be reserved for a replacement character.
   */
  size_t utf8_utf16_strnlen(const char *src, size_t count);
  
  /**
   * utf8_utf16_strlen() - length of a utf-8 string after conversion to utf-16
   *
   * @src:		utf-8 string
   * Return:		length in bytes after conversion to utf-16 without the
   *			trailing \0. -1 if the utf-8 string is not valid.
   */
  #define utf8_utf16_strlen(a) utf8_utf16_strnlen((a), SIZE_MAX)
  
  /**
   * utf8_utf16_strncpy() - copy utf-8 string to utf-16 string
   *
   * @dst:		destination buffer
   * @src:		source buffer
   * @count:		maximum number of code points to copy
   * Return:		-1 if the input parameters are invalid
   */
  int utf8_utf16_strncpy(u16 **dst, const char *src, size_t count);
  
  /**
   * utf8_utf16_strcpy() - copy utf-8 string to utf-16 string
   *
   * @dst:		destination buffer
   * @src:		source buffer
   * Return:		-1 if the input parameters are invalid
   */
  #define utf8_utf16_strcpy(d, s) utf8_utf16_strncpy((d), (s), SIZE_MAX)
  
  /**
   * utf16_get() - get next UTF-16 code point from buffer
   *
   * @src:		pointer to current word, updated to point to next word
   * Return:		code point, or 0 for end of string, or -1 if no legal
   *			code point is found. In case of an error src points to
   *			the incorrect word.
   */
  s32 utf16_get(const u16 **src);
  
  /**
   * utf16_put() - write UTF-16 code point to buffer
   *
   * @code:		code point
   * @dst:		pointer to destination buffer, updated to next position
   * Return:		-1 if the input parameters are invalid
   */
  int utf16_put(s32 code, u16 **dst);
  
  /**
   * utf16_strnlen() - length of a truncated utf-16 string
   *
   * @src:		utf-16 string
   * @count:		maximum number of code points to convert
   * Return:		length in code points. If an invalid UTF-16 sequence is
   *			hit one position will be reserved for a replacement
   *			character.
   */
  size_t utf16_strnlen(const u16 *src, size_t count);
  
  /**
   * utf16_utf8_strnlen() - length of a truncated utf-16 string after conversion
   *			  to utf-8
   *
   * @src:		utf-16 string
   * @count:		maximum number of code points to convert
   * Return:		length in bytes after conversion to utf-8 without the
   *			trailing \0. If an invalid UTF-16 sequence is hit one
   *			byte will be reserved for a replacement character.
   */
  size_t utf16_utf8_strnlen(const u16 *src, size_t count);
  
  /**
   * utf16_utf8_strlen() - length of a utf-16 string after conversion to utf-8
   *
   * @src:		utf-16 string
   * Return:		length in bytes after conversion to utf-8 without the
   *			trailing \0. -1 if the utf-16 string is not valid.
   */
  #define utf16_utf8_strlen(a) utf16_utf8_strnlen((a), SIZE_MAX)
  
  /**
   * utf16_utf8_strncpy() - copy utf-16 string to utf-8 string
   *
   * @dst:		destination buffer
   * @src:		source buffer
   * @count:		maximum number of code points to copy
   * Return:		-1 if the input parameters are invalid
   */
  int utf16_utf8_strncpy(char **dst, const u16 *src, size_t count);
  
  /**
   * utf16_utf8_strcpy() - copy utf-16 string to utf-8 string
   *
   * @dst:		destination buffer
   * @src:		source buffer
   * Return:		-1 if the input parameters are invalid
   */
  #define utf16_utf8_strcpy(d, s) utf16_utf8_strncpy((d), (s), SIZE_MAX)
  
  /**

   * utf_to_lower() - convert a Unicode letter to lower case
   *
   * @code:		letter to convert
   * Return:		lower case letter or unchanged letter
   */
  s32 utf_to_lower(const s32 code);
  
  /**
   * utf_to_upper() - convert a Unicode letter to upper case
   *
   * @code:		letter to convert
   * Return:		upper case letter or unchanged letter
   */
  s32 utf_to_upper(const s32 code);
  
  /**

   * u16_strlen - count non-zero words

   *

   * This function matches wsclen() if the -fshort-wchar compiler flag is set.
   * In the EFI context we explicitly need a function handling u16 strings.

   *

   * @in:			null terminated u16 string
   * ReturnValue:		number of non-zero words.
   *			This is not the number of utf-16 letters!

   */

  size_t u16_strlen(const u16 *in);

  
  /**

   * u16_strlen - count non-zero words

   *

   * This function matches wscnlen_s() if the -fshort-wchar compiler flag is set.
   * In the EFI context we explicitly need a function handling u16 strings.

   *

   * @in:			null terminated u16 string
   * @count:		maximum number of words to count
   * ReturnValue:		number of non-zero words.
   *			This is not the number of utf-16 letters!

   */

  size_t u16_strnlen(const u16 *in, size_t count);

  
  /**

   * u16_strcpy() - copy u16 string
   *
   * Copy u16 string pointed to by src, including terminating null word, to
   * the buffer pointed to by dest.
   *
   * @dest:		destination buffer
   * @src:		source buffer (null terminated)
   * Return:		'dest' address
   */
  u16 *u16_strcpy(u16 *dest, const u16 *src);
  
  /**
   * u16_strdup() - duplicate u16 string
   *
   * Copy u16 string pointed to by src, including terminating null word, to a
   * newly allocated buffer.
   *
   * @src:		source buffer (null terminated)
   * Return:		allocated new buffer on success, NULL on failure
   */
  u16 *u16_strdup(const u16 *src);
  
  /**

   * utf16_to_utf8() - Convert an utf16 string to utf8
   *
   * Converts 'size' characters of the utf16 string 'src' to utf8
   * written to the 'dest' buffer.
   *

   * NOTE that a single utf16 character can generate up to 3 utf8

   * characters.  See MAX_UTF8_PER_UTF16.
   *
   * @dest   the destination buffer to write the utf8 characters
   * @src    the source utf16 string
   * @size   the number of utf16 characters to convert
   * @return the pointer to the first unwritten byte in 'dest'
   */
  uint8_t *utf16_to_utf8(uint8_t *dest, const uint16_t *src, size_t size);
  
  #endif /* __CHARSET_H_ */