// SPDX-License-Identifier: GPL-2.0

  #include <linux/ucs2_string.h>
  #include <linux/module.h>
  
  /* Return the number of unicode characters in data */
  unsigned long
  ucs2_strnlen(const ucs2_char_t *s, size_t maxlength)
  {
          unsigned long length = 0;
  
          while (*s++ != 0 && length < maxlength)
                  length++;
          return length;
  }
  EXPORT_SYMBOL(ucs2_strnlen);
  
  unsigned long
  ucs2_strlen(const ucs2_char_t *s)
  {
          return ucs2_strnlen(s, ~0UL);
  }
  EXPORT_SYMBOL(ucs2_strlen);
  
  /*
   * Return the number of bytes is the length of this string
   * Note: this is NOT the same as the number of unicode characters
   */
  unsigned long
  ucs2_strsize(const ucs2_char_t *data, unsigned long maxlength)
  {
          return ucs2_strnlen(data, maxlength/sizeof(ucs2_char_t)) * sizeof(ucs2_char_t);
  }
  EXPORT_SYMBOL(ucs2_strsize);
  
  int
  ucs2_strncmp(const ucs2_char_t *a, const ucs2_char_t *b, size_t len)
  {
          while (1) {
                  if (len == 0)
                          return 0;
                  if (*a < *b)
                          return -1;
                  if (*a > *b)
                          return 1;
                  if (*a == 0) /* implies *b == 0 */
                          return 0;
                  a++;
                  b++;
                  len--;
          }
  }
  EXPORT_SYMBOL(ucs2_strncmp);

  
  unsigned long
  ucs2_utf8size(const ucs2_char_t *src)
  {
  	unsigned long i;
  	unsigned long j = 0;

  	for (i = 0; src[i]; i++) {

  		u16 c = src[i];

  		if (c >= 0x800)

  			j += 3;

  		else if (c >= 0x80)

  			j += 2;
  		else
  			j += 1;
  	}
  
  	return j;
  }
  EXPORT_SYMBOL(ucs2_utf8size);
  
  /*
   * copy at most maxlength bytes of whole utf8 characters to dest from the
   * ucs2 string src.
   *
   * The return value is the number of characters copied, not including the
   * final NUL character.
   */
  unsigned long
  ucs2_as_utf8(u8 *dest, const ucs2_char_t *src, unsigned long maxlength)
  {
  	unsigned int i;
  	unsigned long j = 0;
  	unsigned long limit = ucs2_strnlen(src, maxlength);
  
  	for (i = 0; maxlength && i < limit; i++) {
  		u16 c = src[i];

  		if (c >= 0x800) {

  			if (maxlength < 3)
  				break;
  			maxlength -= 3;
  			dest[j++] = 0xe0 | (c & 0xf000) >> 12;

  			dest[j++] = 0x80 | (c & 0x0fc0) >> 6;

  			dest[j++] = 0x80 | (c & 0x003f);

  		} else if (c >= 0x80) {

  			if (maxlength < 2)
  				break;
  			maxlength -= 2;

  			dest[j++] = 0xc0 | (c & 0x7c0) >> 6;
  			dest[j++] = 0x80 | (c & 0x03f);

  		} else {
  			maxlength -= 1;
  			dest[j++] = c & 0x7f;
  		}
  	}
  	if (maxlength)
  		dest[j] = '\0';
  	return j;
  }
  EXPORT_SYMBOL(ucs2_as_utf8);

  
  MODULE_LICENSE("GPL v2");