decode_utf8.jl

function decode_utf8(x::Char)
    c = reinterpret(UInt32, x)
    if c < 0x00000080
        return c
    end
    if 0x0000C200 <= c & 0x0000FF00 <= 0x0000DF00
        if c & 0xffff0000 == 0 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
            return (c & 0x0000003F) | ((c & 0x00001F00) >> 2)
        end
    end
    if c & 0x00FF0000 == 0x00E00000
        if c & 0xff000000 == 0 && 0x0000A000 <= c & 0x0000FF00 <= 0x0000BF00 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
           return (c & 0x0000003F) | ((c & 0x00003F00) >> 2) | ((c & 0x000F0000) >> 4)
        end
    end
    if 0x00E10000 <= c & 0x00FF0000 <= 0x00EC0000
        if c & 0xff000000 == 0 && 0x00008000 <= c & 0x0000FF00 <= 0x0000BF00 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
           return (c & 0x0000003F) | ((c & 0x00003F00) >> 2) | ((c & 0x000F0000) >> 4)
        end
    end
    if c & 0x00FF0000 == 0x00ED0000
        if c & 0xff000000 == 0 && 0x00008000 <= c & 0x0000FF00 <= 0x00009F00 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
           return (c & 0x0000003F) | ((c & 0x00003F00) >> 2) | ((c & 0x000F0000) >> 4)
        end
    end
    if 0x00EE0000 <= c & 0x00FF0000 <= 0x00EF0000
        if c & 0xff000000 == 0 && 0x00008000 <= c & 0x0000FF00 <= 0x0000BF00 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
           return (c & 0x0000003F) | ((c & 0x00003F00) >> 2) | ((c & 0x000F0000) >> 4)
        end
    end
    if c & 0xFF000000 == 0xF0000000
        if 0x00900000 <= c & 0x00FF0000 <= 0x00BF0000 && 0x00008000 <= c & 0x0000FF00 <= 0x0000BF00 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
            return (c & 0x0000003F) | ((c & 0x00003F00) >> 2) | ((c & 0x003F0000) >> 4) | (c & 0x07000000 >> 6)
        end
    end
    if 0xF1000000 <= c & 0xFF000000 <= 0xF3000000
        if 0x00800000 <= c & 0x00FF0000 <= 0x00BF0000 && 0x00008000 <= c & 0x0000FF00 <= 0x0000BF00 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
            return (c & 0x0000003F) | ((c & 0x00003F00) >> 2) | ((c & 0x003F0000) >> 4) | (c & 0x07000000 >> 6)
        end
    end
    if c & 0xFF000000 == 0xF4000000
        if 0x00800000 <= c & 0x00FF0000 <= 0x008F0000 && 0x00008000 <= c & 0x0000FF00 <= 0x0000BF00 && 0x00000080 <= c & 0x000000FF <= 0x000000BF
            return (c & 0x0000003F) | ((c & 0x00003F00) >> 2) | ((c & 0x003F0000) >> 4) | (c & 0x07000000 >> 6)
        end
    end
    error("invalid UTF-8")
end