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    mod table;

    use self::table::{DECODE_TABLE, ENCODE_TABLE};
    use crate::hpack::{DecoderError, EncoderError};

    use bytes::{BufMut, BytesMut};

    // Constructed in the generated `table.rs` file
    struct Decoder {
        state: usize,
        maybe_eos: bool,
    }

    // These flags must match the ones in genhuff.rs

    const MAYBE_EOS: u8 = 1;
    const DECODED: u8 = 2;
    const ERROR: u8 = 4;

    pub fn decode(src: &[u8], buf: &mut BytesMut) -> Result<BytesMut, DecoderError> {
        let mut decoder = Decoder::new();

        // Max compression ratio is >= 0.5
        buf.reserve(src.len() << 1);

        for b in src {
            if let Some(b) = decoder.decode4(b >> 4)? {
                buf.put_u8(b);
            }

            if let Some(b) = decoder.decode4(b & 0xf)? {
                buf.put_u8(b);
            }
        }

        if !decoder.is_final() {
            return Err(DecoderError::InvalidHuffmanCode);
        }

        Ok(buf.split())
    }

    // TODO: return error when there is not enough room to encode the value
    pub fn encode<B: BufMut>(src: &[u8], dst: &mut B) -> Result<(), EncoderError> {
        let mut bits: u64 = 0;
        let mut bits_left = 40;
        let mut rem = dst.remaining_mut();

        for &b in src {
            let (nbits, code) = ENCODE_TABLE[b as usize];

            bits |= code << (bits_left - nbits);
            bits_left -= nbits;

            while bits_left <= 32 {
                if rem == 0 {
                    return Err(EncoderError::BufferOverflow);
                }

                dst.put_u8((bits >> 32) as u8);

                bits <<= 8;
                bits_left += 8;
                rem -= 1;
            }
        }

        if bits_left != 40 {
            if rem == 0 {
                return Err(EncoderError::BufferOverflow);
            }

            // This writes the EOS token
            bits |= (1 << bits_left) - 1;
            dst.put_u8((bits >> 32) as u8);
        }

        Ok(())
    }

    impl Decoder {
        fn new() -> Decoder {
            Decoder {
                state: 0,
                maybe_eos: false,
            }
        }

        // Decodes 4 bits
        fn decode4(&mut self, input: u8) -> Result<Option<u8>, DecoderError> {
            // (next-state, byte, flags)
            let (next, byte, flags) = DECODE_TABLE[self.state][input as usize];

            if flags & ERROR == ERROR {
                // Data followed the EOS marker
                return Err(DecoderError::InvalidHuffmanCode);
            }

            let mut ret = None;

            if flags & DECODED == DECODED {
                ret = Some(byte);
            }

            self.state = next;
            self.maybe_eos = flags & MAYBE_EOS == MAYBE_EOS;

            Ok(ret)
        }

        fn is_final(&self) -> bool {
            self.state == 0 || self.maybe_eos
        }
    }

    #[cfg(test)]
    mod test {
        use super::*;

        fn decode(src: &[u8]) -> Result<BytesMut, DecoderError> {
            let mut buf = BytesMut::new();
            super::decode(src, &mut buf)
        }

        #[test]
        fn decode_single_byte() {
            assert_eq!("o", decode(&[0b00111111]).unwrap());
            assert_eq!("0", decode(&[0x0 + 7]).unwrap());
            assert_eq!("A", decode(&[(0x21 << 2) + 3]).unwrap());
        }

        #[test]
        fn single_char_multi_byte() {
            assert_eq!("#", decode(&[255, 160 + 15]).unwrap());
            assert_eq!("$", decode(&[255, 200 + 7]).unwrap());
            assert_eq!("\x0a", decode(&[255, 255, 255, 240 + 3]).unwrap());
        }

        #[test]
        fn multi_char() {
            assert_eq!("!0", decode(&[254, 1]).unwrap());
            assert_eq!(" !", decode(&[0b01010011, 0b11111000]).unwrap());
        }

        #[test]
        fn encode_single_byte() {
            let mut dst = Vec::with_capacity(1);

            encode(b"o", &mut dst).unwrap();
            assert_eq!(&dst[..], &[0b00111111]);

            dst.clear();
            encode(b"0", &mut dst).unwrap();
            assert_eq!(&dst[..], &[0x0 + 7]);

            dst.clear();
            encode(b"A", &mut dst).unwrap();
            assert_eq!(&dst[..], &[(0x21 << 2) + 3]);
        }

        #[test]
        fn encode_decode_str() {
            const DATA: &'static [&'static str] = &[
                "hello world",
                ":method",
                ":scheme",
                ":authority",
                "yahoo.co.jp",
                "GET",
                "http",
                ":path",
                "/images/top/sp2/cmn/logo-ns-130528.png",
                "example.com",
                "hpack-test",
                "xxxxxxx1",
                "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:16.0) Gecko/20100101 Firefox/16.0",
                "accept",
                "Accept",
                "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
                "cookie",
                "B=76j09a189a6h4&b=3&s=0b",
                "TE",
                "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi non bibendum libero. \
                 Etiam ultrices lorem ut.",
            ];

            for s in DATA {
                let mut dst = Vec::with_capacity(s.len());

                encode(s.as_bytes(), &mut dst).unwrap();

                let decoded = decode(&dst).unwrap();

                assert_eq!(&decoded[..], s.as_bytes());
            }
        }

        #[test]
        fn encode_decode_u8() {
            const DATA: &'static [&'static [u8]] =
                &[b"\0", b"\0\0\0", b"\0\x01\x02\x03\x04\x05", b"\xFF\xF8"];

            for s in DATA {
                let mut dst = Vec::with_capacity(s.len());

                encode(s, &mut dst).unwrap();

                let decoded = decode(&dst).unwrap();

                assert_eq!(&decoded[..], &s[..]);
            }
        }
    }