lnsocket 0.5.2

// This is a modification of base32 encoding to support the zbase32 alphabet.
// The original piece of software can be found at https://crates.io/crates/base32(v0.4.0)
// The original portions of this software are Copyright (c) 2015 The base32 Developers

// This file is licensed under either of
// Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0) or
// MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT) at your option.

#[allow(unused)]
use crate::prelude::*;

/// RFC4648 encoding table
const RFC4648_ALPHABET: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";

// Zbase encoding alphabet
//const ZBASE_ALPHABET: &[u8] = b"ybndrfg8ejkmcpqxot1uwisza345h769";

/// RFC4648 decoding table
const RFC4648_INV_ALPHABET: [i8; 43] = [
    -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
    9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
];

/*
// Zbase decoding table
const ZBASE_INV_ALPHABET: [i8; 43] = [
    -1, 18, -1, 25, 26, 27, 30, 29, 7, 31, -1, -1, -1, -1, -1, -1, -1, 24, 1, 12, 3, 8, 5, 6, 28,
    21, 9, 10, -1, 11, 2, 16, 13, 14, 4, 22, 17, 19, -1, 20, 15, 0, 23,
];
*/

/// Alphabet used for encoding and decoding.
#[derive(Copy, Clone)]
pub enum Alphabet {
    /// RFC4648 encoding.
    RFC4648 {
        /// Whether to use padding.
        padding: bool,
    },
    // Zbase32 encoding.
    //ZBase32,
}

impl Alphabet {
    /// Encode bytes into a base32 string.
    pub fn encode(&self, data: &[u8]) -> String {
        // output_length is calculated as follows:
        // / 5 divides the data length by the number of bits per chunk (5),
        // * 8 multiplies the result by the number of characters per chunk (8).
        // + 4 rounds up to the nearest character.
        #[allow(clippy::manual_div_ceil)]
        let output_length = (data.len() * 8 + 4) / 5;
        let mut ret = match self {
            Self::RFC4648 { padding } => {
                let mut ret = Self::encode_data(data, RFC4648_ALPHABET);
                if *padding {
                    let len = ret.len();
                    for i in ret.iter_mut().take(len).skip(output_length) {
                        *i = b'=';
                    }

                    return String::from_utf8(ret).expect("Invalid UTF-8");
                }
                ret
            } //Self::ZBase32 => Self::encode_data(data, ZBASE_ALPHABET),
        };
        ret.truncate(output_length);

        String::from_utf8(ret).expect("Invalid UTF-8")
    }

    /// Decode a base32 string into a byte vector.
    pub fn decode(&self, data: &str) -> Result<Vec<u8>, ()> {
        let data = data.as_bytes();
        let (data, alphabet) = match self {
            Self::RFC4648 { padding } => {
                let mut unpadded_data_length = data.len();
                if *padding {
                    if data.len() % 8 != 0 {
                        return Err(());
                    }
                    data.iter().rev().take(6).for_each(|&c| {
                        if c == b'=' {
                            unpadded_data_length -= 1;
                        }
                    });
                }
                (&data[..unpadded_data_length], RFC4648_INV_ALPHABET)
            } //Self::ZBase32 => (data, ZBASE_INV_ALPHABET),
        };
        // If the string has more characters than are required to alphabet_encode the number of bytes
        // decodable, treat the string as invalid.
        match data.len() % 8 {
            1 | 3 | 6 => return Err(()),
            _ => {}
        }
        Self::decode_data(data, alphabet)
    }

    /// Encode a byte slice into a base32 string.
    fn encode_data(data: &[u8], alphabet: &'static [u8]) -> Vec<u8> {
        // cap is calculated as follows:
        // / 5 divides the data length by the number of bits per chunk (5),
        // * 8 multiplies the result by the number of characters per chunk (8).
        // + 4 rounds up to the nearest character.
        let cap = data.len().div_ceil(5);
        let mut ret = Vec::with_capacity(cap);
        for chunk in data.chunks(5) {
            let mut buf = [0u8; 5];
            for (i, &b) in chunk.iter().enumerate() {
                buf[i] = b;
            }
            ret.push(alphabet[((buf[0] & 0xF8) >> 3) as usize]);
            ret.push(alphabet[(((buf[0] & 0x07) << 2) | ((buf[1] & 0xC0) >> 6)) as usize]);
            ret.push(alphabet[((buf[1] & 0x3E) >> 1) as usize]);
            ret.push(alphabet[(((buf[1] & 0x01) << 4) | ((buf[2] & 0xF0) >> 4)) as usize]);
            ret.push(alphabet[(((buf[2] & 0x0F) << 1) | (buf[3] >> 7)) as usize]);
            ret.push(alphabet[((buf[3] & 0x7C) >> 2) as usize]);
            ret.push(alphabet[(((buf[3] & 0x03) << 3) | ((buf[4] & 0xE0) >> 5)) as usize]);
            ret.push(alphabet[(buf[4] & 0x1F) as usize]);
        }

        ret
    }

    fn decode_data(data: &[u8], alphabet: [i8; 43]) -> Result<Vec<u8>, ()> {
        // cap is calculated as follows:
        // / 8 divides the data length by the number of characters per chunk (8),
        // * 5 multiplies the result by the number of bits per chunk (5),
        // + 7 rounds up to the nearest byte.
        let cap = data.len().div_ceil(8);
        let mut ret = Vec::with_capacity(cap);
        for chunk in data.chunks(8) {
            let mut buf = [0u8; 8];
            for (i, &c) in chunk.iter().enumerate() {
                match alphabet.get(c.to_ascii_uppercase().wrapping_sub(b'0') as usize) {
                    Some(&-1) | None => return Err(()),
                    Some(&value) => buf[i] = value as u8,
                };
            }
            ret.push((buf[0] << 3) | (buf[1] >> 2));
            ret.push((buf[1] << 6) | (buf[2] << 1) | (buf[3] >> 4));
            ret.push((buf[3] << 4) | (buf[4] >> 1));
            ret.push((buf[4] << 7) | (buf[5] << 2) | (buf[6] >> 3));
            ret.push((buf[6] << 5) | buf[7]);
        }
        let output_length = data.len() * 5 / 8;
        for c in ret.drain(output_length..) {
            if c != 0 {
                // If the original string had any bits set at positions outside of the encoded data,
                // treat the string as invalid.
                return Err(());
            }
        }

        // Check that our capacity calculation doesn't under-shoot in fuzzing
        Ok(ret)
    }
}

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

    const RFC4648_NON_PADDED_TEST_VECTORS: &[(&[u8], &[u8])] = &[
        (&[0xF8, 0x3E, 0x7F, 0x83, 0xE7], b"7A7H7A7H"),
        (&[0x77, 0xC1, 0xF7, 0x7C, 0x1F], b"O7A7O7A7"),
        (&[0xF8, 0x3E, 0x7F, 0x83, 0xE7], b"7A7H7A7H"),
        (&[0x77, 0xC1, 0xF7, 0x7C, 0x1F], b"O7A7O7A7"),
    ];

    const RFC4648_TEST_VECTORS: &[(&[u8], &str)] = &[
        (b"", ""),
        (b"f", "MY======"),
        (b"fo", "MZXQ===="),
        (b"foo", "MZXW6==="),
        (b"foob", "MZXW6YQ="),
        (b"fooba", "MZXW6YTB"),
        (b"foobar", "MZXW6YTBOI======"),
        (&[0xF8, 0x3E, 0x7F, 0x83], "7A7H7AY="),
    ];

    #[test]
    fn test_rfc4648_encode() {
        for (input, encoded) in RFC4648_TEST_VECTORS {
            assert_eq!(&Alphabet::RFC4648 { padding: true }.encode(input), encoded);
        }

        for (input, encoded) in RFC4648_NON_PADDED_TEST_VECTORS {
            assert_eq!(
                &Alphabet::RFC4648 { padding: false }
                    .encode(input)
                    .as_bytes(),
                encoded
            );
        }
    }

    #[test]
    fn test_rfc4648_decode() {
        for (input, encoded) in RFC4648_TEST_VECTORS {
            let res = &Alphabet::RFC4648 { padding: true }.decode(encoded).unwrap();
            assert_eq!(&res[..], &input[..]);
        }

        for (input, encoded) in RFC4648_NON_PADDED_TEST_VECTORS {
            let res = &Alphabet::RFC4648 { padding: false }
                .decode(std::str::from_utf8(encoded).unwrap())
                .unwrap();
            assert_eq!(&res[..], &input[..]);
        }
    }

    #[test]
    fn padding() {
        let num_padding = [0, 6, 4, 3, 1];
        for i in 1..6 {
            let encoded = Alphabet::RFC4648 { padding: true }
                .encode((0..(i as u8)).collect::<Vec<u8>>().as_ref());
            assert_eq!(encoded.len(), 8);
            for j in 0..(num_padding[i % 5]) {
                assert_eq!(encoded.as_bytes()[encoded.len() - j - 1], b'=');
            }
            for j in 0..(8 - num_padding[i % 5]) {
                assert!(encoded.as_bytes()[j] != b'=');
            }
        }
    }

    #[test]
    fn test_decode_rfc4648_errors() {
        assert!(
            Alphabet::RFC4648 { padding: false }
                .decode("abc2def===")
                .is_err()
        ); // Invalid char because padding is disabled
        assert!(
            Alphabet::RFC4648 { padding: true }
                .decode("abc2def===")
                .is_err()
        ); // Invalid length
        assert!(
            Alphabet::RFC4648 { padding: true }
                .decode("MZX=6YTB")
                .is_err()
        ); // Invalid char
    }
}