/*
   *  charset conversion utils
   *
   *  Copyright (c) 2017 Rob Clark
   *
   *  SPDX-License-Identifier:     GPL-2.0+
   */
  
  #ifndef __CHARSET_H_
  #define __CHARSET_H_
  
  #include <linux/types.h>
  
  #define MAX_UTF8_PER_UTF16 3
  
  /**
   * utf16_strlen() - Get the length of an utf16 string
   *
   * Returns the number of 16 bit characters in an utf16 string, not
   * including the terminating NULL character.
   *
   * @in     the string to measure
   * @return the string length
   */
  size_t utf16_strlen(const uint16_t *in);
  
  /**
   * utf16_strnlen() - Get the length of a fixed-size utf16 string.
   *
   * Returns the number of 16 bit characters in an utf16 string,
   * not including the terminating NULL character, but at most
   * 'count' number of characters.  In doing this, utf16_strnlen()
   * looks at only the first 'count' characters.
   *
   * @in     the string to measure
   * @count  the maximum number of characters to count
   * @return the string length, up to a maximum of 'count'
   */
  size_t utf16_strnlen(const uint16_t *in, size_t count);
  
  /**
   * utf16_strcpy() - UTF16 equivalent of strcpy()
   */
  uint16_t *utf16_strcpy(uint16_t *dest, const uint16_t *src);
  
  /**
   * utf16_strdup() - UTF16 equivalent of strdup()
   */
  uint16_t *utf16_strdup(const uint16_t *s);
  
  /**
   * 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);
  
  /**
   * utf8_to_utf16() - Convert an utf8 string to utf16
   *
   * Converts up to 'size' characters of the utf16 string 'src' to utf8
   * written to the 'dest' buffer. Stops at 0x00.
   *
   * @dest   the destination buffer to write the utf8 characters
   * @src    the source utf16 string
   * @size   maximum number of utf16 characters to convert
   * @return the pointer to the first unwritten byte in 'dest'
   */
  uint16_t *utf8_to_utf16(uint16_t *dest, const uint8_t *src, size_t size);
  
  #endif /* __CHARSET_H_ */