sark_core/http/

huffman.rs

pub struct HpackHuffman;

pub const CODES: [(u32, u8); 257] = [
    (0x1ff8, 13),
    (0x7fffd8, 23),
    (0xfffffe2, 28),
    (0xfffffe3, 28),
    (0xfffffe4, 28),
    (0xfffffe5, 28),
    (0xfffffe6, 28),
    (0xfffffe7, 28),
    (0xfffffe8, 28),
    (0xffffea, 24),
    (0x3ffffffc, 30),
    (0xfffffe9, 28),
    (0xfffffea, 28),
    (0x3ffffffd, 30),
    (0xfffffeb, 28),
    (0xfffffec, 28),
    (0xfffffed, 28),
    (0xfffffee, 28),
    (0xfffffef, 28),
    (0xffffff0, 28),
    (0xffffff1, 28),
    (0xffffff2, 28),
    (0x3ffffffe, 30),
    (0xffffff3, 28),
    (0xffffff4, 28),
    (0xffffff5, 28),
    (0xffffff6, 28),
    (0xffffff7, 28),
    (0xffffff8, 28),
    (0xffffff9, 28),
    (0xffffffa, 28),
    (0xffffffb, 28),
    (0x14, 6),
    (0x3f8, 10),
    (0x3f9, 10),
    (0xffa, 12),
    (0x1ff9, 13),
    (0x15, 6),
    (0xf8, 8),
    (0x7fa, 11),
    (0x3fa, 10),
    (0x3fb, 10),
    (0xf9, 8),
    (0x7fb, 11),
    (0xfa, 8),
    (0x16, 6),
    (0x17, 6),
    (0x18, 6),
    (0x0, 5),
    (0x1, 5),
    (0x2, 5),
    (0x19, 6),
    (0x1a, 6),
    (0x1b, 6),
    (0x1c, 6),
    (0x1d, 6),
    (0x1e, 6),
    (0x1f, 6),
    (0x5c, 7),
    (0xfb, 8),
    (0x7ffc, 15),
    (0x20, 6),
    (0xffb, 12),
    (0x3fc, 10),
    (0x1ffa, 13),
    (0x21, 6),
    (0x5d, 7),
    (0x5e, 7),
    (0x5f, 7),
    (0x60, 7),
    (0x61, 7),
    (0x62, 7),
    (0x63, 7),
    (0x64, 7),
    (0x65, 7),
    (0x66, 7),
    (0x67, 7),
    (0x68, 7),
    (0x69, 7),
    (0x6a, 7),
    (0x6b, 7),
    (0x6c, 7),
    (0x6d, 7),
    (0x6e, 7),
    (0x6f, 7),
    (0x70, 7),
    (0x71, 7),
    (0x72, 7),
    (0xfc, 8),
    (0x73, 7),
    (0xfd, 8),
    (0x1ffb, 13),
    (0x7fff0, 19),
    (0x1ffc, 13),
    (0x3ffc, 14),
    (0x22, 6),
    (0x7ffd, 15),
    (0x3, 5),
    (0x23, 6),
    (0x4, 5),
    (0x24, 6),
    (0x5, 5),
    (0x25, 6),
    (0x26, 6),
    (0x27, 6),
    (0x6, 5),
    (0x74, 7),
    (0x75, 7),
    (0x28, 6),
    (0x29, 6),
    (0x2a, 6),
    (0x7, 5),
    (0x2b, 6),
    (0x76, 7),
    (0x2c, 6),
    (0x8, 5),
    (0x9, 5),
    (0x2d, 6),
    (0x77, 7),
    (0x78, 7),
    (0x79, 7),
    (0x7a, 7),
    (0x7b, 7),
    (0x7ffe, 15),
    (0x7fc, 11),
    (0x3ffd, 14),
    (0x1ffd, 13),
    (0xffffffc, 28),
    (0xfffe6, 20),
    (0x3fffd2, 22),
    (0xfffe7, 20),
    (0xfffe8, 20),
    (0x3fffd3, 22),
    (0x3fffd4, 22),
    (0x3fffd5, 22),
    (0x7fffd9, 23),
    (0x3fffd6, 22),
    (0x7fffda, 23),
    (0x7fffdb, 23),
    (0x7fffdc, 23),
    (0x7fffdd, 23),
    (0x7fffde, 23),
    (0xffffeb, 24),
    (0x7fffdf, 23),
    (0xffffec, 24),
    (0xffffed, 24),
    (0x3fffd7, 22),
    (0x7fffe0, 23),
    (0xffffee, 24),
    (0x7fffe1, 23),
    (0x7fffe2, 23),
    (0x7fffe3, 23),
    (0x7fffe4, 23),
    (0x1fffdc, 21),
    (0x3fffd8, 22),
    (0x7fffe5, 23),
    (0x3fffd9, 22),
    (0x7fffe6, 23),
    (0x7fffe7, 23),
    (0xffffef, 24),
    (0x3fffda, 22),
    (0x1fffdd, 21),
    (0xfffe9, 20),
    (0x3fffdb, 22),
    (0x3fffdc, 22),
    (0x7fffe8, 23),
    (0x7fffe9, 23),
    (0x1fffde, 21),
    (0x7fffea, 23),
    (0x3fffdd, 22),
    (0x3fffde, 22),
    (0xfffff0, 24),
    (0x1fffdf, 21),
    (0x3fffdf, 22),
    (0x7fffeb, 23),
    (0x7fffec, 23),
    (0x1fffe0, 21),
    (0x1fffe1, 21),
    (0x3fffe0, 22),
    (0x1fffe2, 21),
    (0x7fffed, 23),
    (0x3fffe1, 22),
    (0x7fffee, 23),
    (0x7fffef, 23),
    (0xfffea, 20),
    (0x3fffe2, 22),
    (0x3fffe3, 22),
    (0x3fffe4, 22),
    (0x7ffff0, 23),
    (0x3fffe5, 22),
    (0x3fffe6, 22),
    (0x7ffff1, 23),
    (0x3ffffe0, 26),
    (0x3ffffe1, 26),
    (0xfffeb, 20),
    (0x7fff1, 19),
    (0x3fffe7, 22),
    (0x7ffff2, 23),
    (0x3fffe8, 22),
    (0x1ffffec, 25),
    (0x3ffffe2, 26),
    (0x3ffffe3, 26),
    (0x3ffffe4, 26),
    (0x7ffffde, 27),
    (0x7ffffdf, 27),
    (0x3ffffe5, 26),
    (0xfffff1, 24),
    (0x1ffffed, 25),
    (0x7fff2, 19),
    (0x1fffe3, 21),
    (0x3ffffe6, 26),
    (0x7ffffe0, 27),
    (0x7ffffe1, 27),
    (0x3ffffe7, 26),
    (0x7ffffe2, 27),
    (0xfffff2, 24),
    (0x1fffe4, 21),
    (0x1fffe5, 21),
    (0x3ffffe8, 26),
    (0x3ffffe9, 26),
    (0xffffffd, 28),
    (0x7ffffe3, 27),
    (0x7ffffe4, 27),
    (0x7ffffe5, 27),
    (0xfffec, 20),
    (0xfffff3, 24),
    (0xfffed, 20),
    (0x1fffe6, 21),
    (0x3fffe9, 22),
    (0x1fffe7, 21),
    (0x1fffe8, 21),
    (0x7ffff3, 23),
    (0x3fffea, 22),
    (0x3fffeb, 22),
    (0x1ffffee, 25),
    (0x1ffffef, 25),
    (0xfffff4, 24),
    (0xfffff5, 24),
    (0x3ffffea, 26),
    (0x7ffff4, 23),
    (0x3ffffeb, 26),
    (0x7ffffe6, 27),
    (0x3ffffec, 26),
    (0x3ffffed, 26),
    (0x7ffffe7, 27),
    (0x7ffffe8, 27),
    (0x7ffffe9, 27),
    (0x7ffffea, 27),
    (0x7ffffeb, 27),
    (0xffffffe, 28),
    (0x7ffffec, 27),
    (0x7ffffed, 27),
    (0x7ffffee, 27),
    (0x7ffffef, 27),
    (0x7fffff0, 27),
    (0x3ffffee, 26),
    (0x3fffffff, 30),
];

impl HpackHuffman {
    pub fn encoded_len(input: &[u8]) -> usize {
        let mut bits: u64 = 0;
        for &b in input {
            bits += CODES[b as usize].1 as u64;
        }
        bits.div_ceil(8) as usize
    }

    pub fn encode(input: &[u8], out: &mut Vec<u8>) {
        let mut buffer: u64 = 0;
        let mut bits_in: u32 = 0;
        for &b in input {
            let (code, len) = CODES[b as usize];
            let len = len as u32;
            buffer = (buffer << len) | (code as u64);
            bits_in += len;
            while bits_in >= 8 {
                bits_in -= 8;
                out.push((buffer >> bits_in) as u8);
            }
        }
        if bits_in > 0 {
            let pad_bits = 8 - bits_in;
            buffer = (buffer << pad_bits) | ((1u64 << pad_bits) - 1);
            out.push(buffer as u8);
        }
    }

    pub fn decode(input: &[u8], out: &mut Vec<u8>) -> Result<(), HpackHuffmanError> {
        let mut buffer: u64 = 0;
        let mut bits_in: u32 = 0;
        let total_bits: u64 = (input.len() as u64) * 8;
        let mut consumed_bits: u64 = 0;
        let mut input_pos: usize = 0;
        loop {
            while bits_in < 30 && input_pos < input.len() {
                buffer = (buffer << 8) | (input[input_pos] as u64);
                input_pos += 1;
                bits_in += 8;
            }
            if bits_in == 0 {
                return Ok(());
            }
            let mut matched = false;
            for (sym, &(code, len)) in CODES.iter().take(256).enumerate() {
                let len = len as u32;
                if len > bits_in {
                    continue;
                }
                let candidate = ((buffer >> (bits_in - len)) & ((1u64 << len) - 1)) as u32;
                if candidate == code {
                    if consumed_bits + len as u64 > total_bits {
                        return Err(HpackHuffmanError);
                    }
                    out.push(sym as u8);
                    bits_in -= len;
                    consumed_bits += len as u64;
                    buffer &= (1u64 << bits_in) - 1;
                    matched = true;
                    break;
                }
            }
            if matched {
                continue;
            }
            if input_pos >= input.len() {
                let remaining = bits_in;
                if remaining == 0 {
                    return Ok(());
                }
                if remaining > 7 {
                    return Err(HpackHuffmanError);
                }
                let expected = (1u64 << remaining) - 1;
                let tail = buffer & expected;
                if tail == expected {
                    return Ok(());
                }
                return Err(HpackHuffmanError);
            }
            return Err(HpackHuffmanError);
        }
    }
}

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct HpackHuffmanError;