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use crate::descriptor::DescriptorError;
use alloc::string::String;
const INPUT_CHARSET: &[u8] = b"0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ ";
const CHECKSUM_CHARSET: &[u8] = b"qpzry9x8gf2tvdw0s3jn54khce6mua7l";
fn poly_mod(mut c: u64, val: u64) -> u64 {
let c0 = c >> 35;
c = ((c & 0x7ffffffff) << 5) ^ val;
if c0 & 1 > 0 {
c ^= 0xf5dee51989
};
if c0 & 2 > 0 {
c ^= 0xa9fdca3312
};
if c0 & 4 > 0 {
c ^= 0x1bab10e32d
};
if c0 & 8 > 0 {
c ^= 0x3706b1677a
};
if c0 & 16 > 0 {
c ^= 0x644d626ffd
};
c
}
pub fn calc_checksum_bytes(mut desc: &str) -> Result<[u8; 8], DescriptorError> {
let mut c = 1;
let mut cls = 0;
let mut clscount = 0;
let mut original_checksum = None;
if let Some(split) = desc.split_once('#') {
desc = split.0;
original_checksum = Some(split.1);
}
for ch in desc.as_bytes() {
let pos = INPUT_CHARSET
.iter()
.position(|b| b == ch)
.ok_or(DescriptorError::InvalidDescriptorCharacter(*ch))? as u64;
c = poly_mod(c, pos & 31);
cls = cls * 3 + (pos >> 5);
clscount += 1;
if clscount == 3 {
c = poly_mod(c, cls);
cls = 0;
clscount = 0;
}
}
if clscount > 0 {
c = poly_mod(c, cls);
}
(0..8).for_each(|_| c = poly_mod(c, 0));
c ^= 1;
let mut checksum = [0_u8; 8];
for j in 0..8 {
checksum[j] = CHECKSUM_CHARSET[((c >> (5 * (7 - j))) & 31) as usize];
}
if let Some(original_checksum) = original_checksum {
if original_checksum.as_bytes() != checksum {
return Err(DescriptorError::InvalidDescriptorChecksum);
}
}
Ok(checksum)
}
pub fn calc_checksum(desc: &str) -> Result<String, DescriptorError> {
calc_checksum_bytes(desc).map(|b| unsafe { String::from_utf8_unchecked(b.to_vec()) })
}
#[cfg(test)]
mod test {
use super::*;
use crate::descriptor::calc_checksum;
use assert_matches::assert_matches;
#[test]
fn test_calc_checksum() {
let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)";
assert_eq!(calc_checksum(desc).unwrap(), "tqz0nc62");
let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)";
assert_eq!(calc_checksum(desc).unwrap(), "lasegmfs");
}
#[test]
fn test_calc_checksum_with_checksum_hash() {
let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)#tqz0nc62";
assert_eq!(calc_checksum(desc).unwrap(), "tqz0nc62");
let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)#lasegmfs";
assert_eq!(calc_checksum(desc).unwrap(), "lasegmfs");
let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)#tqz0nc26";
assert_matches!(
calc_checksum(desc),
Err(DescriptorError::InvalidDescriptorChecksum)
);
let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)#lasegmsf";
assert_matches!(
calc_checksum(desc),
Err(DescriptorError::InvalidDescriptorChecksum)
);
}
#[test]
fn test_calc_checksum_invalid_character() {
let sparkle_heart = unsafe { core::str::from_utf8_unchecked(&[240, 159, 146, 150]) };
let invalid_desc = format!("wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcL{}fjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)", sparkle_heart);
assert_matches!(
calc_checksum(&invalid_desc),
Err(DescriptorError::InvalidDescriptorCharacter(invalid_char)) if invalid_char == sparkle_heart.as_bytes()[0]
);
}
}