Function codepoint_to_utf8

3rdparty/lua/lua-cjson/lua_cjson.c:803–836

Converts a Unicode codepoint to UTF-8. * Returns UTF-8 string length, and up to 4 bytes in *utf8 */

/* Converts a Unicode codepoint to UTF-8.
 * Returns UTF-8 string length, and up to 4 bytes in *utf8 */
static int codepoint_to_utf8(char *utf8, int codepoint)
{
    /* 0xxxxxxx */
    if (codepoint <= 0x7F) {
        utf8[0] = codepoint;
        return 1;
    }

    /* 110xxxxx 10xxxxxx */
    if (codepoint <= 0x7FF) {
        utf8[0] = (codepoint >> 6) | 0xC0;
        utf8[1] = (codepoint & 0x3F) | 0x80;
        return 2;
    }

    /* 1110xxxx 10xxxxxx 10xxxxxx */
    if (codepoint <= 0xFFFF) {
        utf8[0] = (codepoint >> 12) | 0xE0;
        utf8[1] = ((codepoint >> 6) & 0x3F) | 0x80;
        utf8[2] = (codepoint & 0x3F) | 0x80;
        return 3;
    }

    /* 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
    if (codepoint <= 0x1FFFFF) {
        utf8[0] = (codepoint >> 18) | 0xF0;
        utf8[1] = ((codepoint >> 12) & 0x3F) | 0x80;
        utf8[2] = ((codepoint >> 6) & 0x3F) | 0x80;
        utf8[3] = (codepoint & 0x3F) | 0x80;
        return 4;
    }

    return 0;
}


/* Called when index pointing to beginning of UTF-16 code escape: \uXXXX