module std+, utf8 {

    private import rt::c;

    var utf8table() int = { 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 1, 1 };

    // See Copyright Notice at the end of this file.
    func utf8decode(o. char, val. int = null) .char {
        define {
            MAXUNICODE = 0x10ffff;
        }
        static limits() uint = { 0xff, 0x7f, 0x7ff, 0xffff };
        var s. char = o;
        var c uint = s[0];
        var res uint = 0;
        if c < 0x80 {
            res = c;
        else
            var count int = 0;
            while c & 0x40 {
                var cc int = s[++count];
                if (cc & 0xc0) ~= 0x80;
                    return null;
                res = (res << 6) | (cc & 0x3f);
                c <<= 1;
            }
            res |= ((c & 0x7f) << (count * 5));
            if count > 3 or res > MAXUNICODE or res <= limits[count];
                return null;
            s += count;
        }
        if val ~= null;
            .val = res;
        return s + 1;
    }

    func utf8len_s(s. char, size int, tail. int = null) int {
        func = 0;
        if tail ~= null;
            .tail = 0;
        forvar pos int = 0; pos < size; func++ {
            var s1. char = utf8decode(s + pos);
            if s1 == null;
                return -1;
            if tail ~= null;
                .tail = s1 - (s + pos);
            pos = s1 - s;
        }
    }

    inline utf8chk(s. char, size int) bool {
        return utf8len_s(s, size) ~= -1;
    }

    func utf8len(s. char, tail. int = null) int {
        if tail ~= null;
            .tail = 0;
        for func = 0;; func++ {
            var val int;
            var s1. char = utf8decode(s, &val);
            if s1 == null;
                return -1;
            if !val;
                return;
            if tail ~= null;
                .tail = s1 - s;
            s = s1;
        }
    }

    func utf8size(s. char, tail. int = null) int {
        var o. char = s;
        if tail ~= null;
            .tail = 0;
        for ;; {
            var val int;
            var s1. char = utf8decode(s, &val);
            if s1 == null;
                return -1;
            if !val;
                return (s1 - 1) - o;
            if tail ~= null;
                .tail = s1 - s;
            s = s1;
        }
    }

    func utf8at(s. char, idx int, c. uint32) int {
        forvar i int = 0;; i++ {
            var val int;
            var s1. char = utf8decode(s, &val);
            if s1 == null;
                return -1;
            if i >= idx {
                .c = val;
                return s1 - s;
            }
            s = s1;
        }
    }

    func utf8cmp(s1. char, s2. char) bool {
        var ss1 int = utf8size(s1);
        var ss2 int = utf8size(s2);
        if ss1 ~= -1 and ss1 == ss2 and !memcmp(s1, s2, ss1);
            return true;
        return false;
    }

    func utf8str(s. char, sub. char) .char {
        var s1 int = utf8size(s),
            s2 int = utf8size(sub);
        if s1 == -1 or s2 == -1;
            return null;
        return memmem(s, s1, sub, s2);
    }

}

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*
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