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use std::iter::FromIterator;
use crate::descriptor::Error;
const INPUT_CHARSET: &str = "0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ ";
const CHECKSUM_CHARSET: &str = "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 get_checksum(desc: &str) -> Result<String, Error> {
let mut c = 1;
let mut cls = 0;
let mut clscount = 0;
for ch in desc.chars() {
let pos = INPUT_CHARSET
.find(ch)
.ok_or(Error::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 chars = Vec::with_capacity(8);
for j in 0..8 {
chars.push(
CHECKSUM_CHARSET
.chars()
.nth(((c >> (5 * (7 - j))) & 31) as usize)
.unwrap(),
);
}
Ok(String::from_iter(chars))
}
#[cfg(test)]
mod test {
use super::*;
use crate::descriptor::get_checksum;
#[test]
fn test_get_checksum() {
let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)";
assert_eq!(get_checksum(desc).unwrap(), "tqz0nc62");
let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)";
assert_eq!(get_checksum(desc).unwrap(), "lasegmfs");
}
#[test]
fn test_get_checksum_invalid_character() {
let sparkle_heart = vec![240, 159, 146, 150];
let sparkle_heart = std::str::from_utf8(&sparkle_heart)
.unwrap()
.chars()
.next()
.unwrap();
let invalid_desc = format!("wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcL{}fjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)", sparkle_heart);
assert!(matches!(
get_checksum(&invalid_desc).err(),
Some(Error::InvalidDescriptorCharacter(invalid_char)) if invalid_char == sparkle_heart
));
}
}