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    // Pulled from std::char until encode_utf8 stabilizes. ---AG

    // UTF-8 ranges and tags for encoding characters
    const TAG_CONT: u8    = 0b1000_0000;
    const TAG_TWO_B: u8   = 0b1100_0000;
    const TAG_THREE_B: u8 = 0b1110_0000;
    const TAG_FOUR_B: u8  = 0b1111_0000;
    const MAX_ONE_B: u32   =     0x80;
    const MAX_TWO_B: u32   =    0x800;
    const MAX_THREE_B: u32 =  0x10000;

    #[inline]
    pub fn encode_utf8(character: char, dst: &mut [u8]) -> Option<usize> {
        let code = character as u32;
        if code < MAX_ONE_B && !dst.is_empty() {
            dst[0] = code as u8;
            Some(1)
        } else if code < MAX_TWO_B && dst.len() >= 2 {
            dst[0] = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
            dst[1] = (code & 0x3F) as u8 | TAG_CONT;
            Some(2)
        } else if code < MAX_THREE_B && dst.len() >= 3  {
            dst[0] = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
            dst[1] = (code >>  6 & 0x3F) as u8 | TAG_CONT;
            dst[2] = (code & 0x3F) as u8 | TAG_CONT;
            Some(3)
        } else if dst.len() >= 4 {
            dst[0] = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
            dst[1] = (code >> 12 & 0x3F) as u8 | TAG_CONT;
            dst[2] = (code >>  6 & 0x3F) as u8 | TAG_CONT;
            dst[3] = (code & 0x3F) as u8 | TAG_CONT;
            Some(4)
        } else {
            None
        }
    }

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