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  • /*
     *  charset conversion utils
     *
     *  Copyright (c) 2017 Rob Clark
     *
     *  SPDX-License-Identifier:     GPL-2.0+
     */
    
    #ifndef __CHARSET_H_
    #define __CHARSET_H_
    
    #define MAX_UTF8_PER_UTF16 4
    
    /**
     * 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 4 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_ */