// SPDX-License-Identifier: CC0-1.0
//! Bitcoin base58 encoding and decoding.
//!
//! This crate can be used in a no-std environment but requires an allocator.
#![no_std]
// Experimental features we need.
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
#![cfg_attr(bench, feature(test))]
// Coding conventions.
#![warn(missing_docs)]
// Instead of littering the codebase for non-fuzzing code just globally allow.
#![cfg_attr(fuzzing, allow(dead_code, unused_imports))]
// Exclude lints we don't think are valuable.
#![allow(clippy::needless_question_mark)] // https://github.com/rust-bitcoin/rust-bitcoin/pull/2134
#![allow(clippy::manual_range_contains)] // More readable than clippy's format.
#[macro_use]
extern crate alloc;
#[cfg(feature = "std")]
extern crate std;
static BASE58_CHARS: &[u8] = b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
pub mod error;
#[cfg(not(feature = "std"))]
pub use alloc::{string::String, vec::Vec};
use core::{fmt, iter, slice, str};
#[cfg(feature = "std")]
pub use std::{string::String, vec::Vec};
use hashes::{sha256d, Hash};
#[rustfmt::skip] // Keep public re-exports separate.
#[doc(inline)]
pub use self::error::Error;
#[rustfmt::skip]
static BASE58_DIGITS: [Option<u8>; 128] = [
None, None, None, None, None, None, None, None, // 0-7
None, None, None, None, None, None, None, None, // 8-15
None, None, None, None, None, None, None, None, // 16-23
None, None, None, None, None, None, None, None, // 24-31
None, None, None, None, None, None, None, None, // 32-39
None, None, None, None, None, None, None, None, // 40-47
None, Some(0), Some(1), Some(2), Some(3), Some(4), Some(5), Some(6), // 48-55
Some(7), Some(8), None, None, None, None, None, None, // 56-63
None, Some(9), Some(10), Some(11), Some(12), Some(13), Some(14), Some(15), // 64-71
Some(16), None, Some(17), Some(18), Some(19), Some(20), Some(21), None, // 72-79
Some(22), Some(23), Some(24), Some(25), Some(26), Some(27), Some(28), Some(29), // 80-87
Some(30), Some(31), Some(32), None, None, None, None, None, // 88-95
None, Some(33), Some(34), Some(35), Some(36), Some(37), Some(38), Some(39), // 96-103
Some(40), Some(41), Some(42), Some(43), None, Some(44), Some(45), Some(46), // 104-111
Some(47), Some(48), Some(49), Some(50), Some(51), Some(52), Some(53), Some(54), // 112-119
Some(55), Some(56), Some(57), None, None, None, None, None, // 120-127
];
/// Decodes a base58-encoded string into a byte vector.
pub fn decode(data: &str) -> Result<Vec<u8>, Error> {
// 11/15 is just over log_256(58)
let mut scratch = vec![0u8; 1 + data.len() * 11 / 15];
// Build in base 256
for d58 in data.bytes() {
// Compute "X = X * 58 + next_digit" in base 256
if d58 as usize >= BASE58_DIGITS.len() {
return Err(Error::BadByte(d58));
}
let mut carry = match BASE58_DIGITS[d58 as usize] {
Some(d58) => d58 as u32,
None => {
return Err(Error::BadByte(d58));
}
};
for d256 in scratch.iter_mut().rev() {
carry += *d256 as u32 * 58;
*d256 = carry as u8;
carry /= 256;
}
assert_eq!(carry, 0);
}
// Copy leading zeroes directly
let mut ret: Vec<u8> = data.bytes().take_while(|&x| x == BASE58_CHARS[0]).map(|_| 0).collect();
// Copy rest of string
ret.extend(scratch.into_iter().skip_while(|&x| x == 0));
Ok(ret)
}
/// Decodes a base58check-encoded string into a byte vector verifying the checksum.
pub fn decode_check(data: &str) -> Result<Vec<u8>, Error> {
let mut ret: Vec<u8> = decode(data)?;
if ret.len() < 4 {
return Err(Error::TooShort(ret.len()));
}
let check_start = ret.len() - 4;
let hash_check =
sha256d::Hash::hash(&ret[..check_start])[..4].try_into().expect("4 byte slice");
let data_check = ret[check_start..].try_into().expect("4 byte slice");
let expected = u32::from_le_bytes(hash_check);
let actual = u32::from_le_bytes(data_check);
if expected != actual {
return Err(Error::BadChecksum(expected, actual));
}
ret.truncate(check_start);
Ok(ret)
}
/// Encodes `data` as a base58 string (see also `base58::encode_check()`).
pub fn encode(data: &[u8]) -> String { encode_iter(data.iter().cloned()) }
/// Encodes `data` as a base58 string including the checksum.
///
/// The checksum is the first four bytes of the sha256d of the data, concatenated onto the end.
pub fn encode_check(data: &[u8]) -> String {
let checksum = sha256d::Hash::hash(data);
encode_iter(data.iter().cloned().chain(checksum[0..4].iter().cloned()))
}
/// Encodes a slice as base58, including the checksum, into a formatter.
///
/// The checksum is the first four bytes of the sha256d of the data, concatenated onto the end.
pub fn encode_check_to_fmt(fmt: &mut fmt::Formatter, data: &[u8]) -> fmt::Result {
let checksum = sha256d::Hash::hash(data);
let iter = data.iter().cloned().chain(checksum[0..4].iter().cloned());
format_iter(fmt, iter)
}
fn encode_iter<I>(data: I) -> String
where
I: Iterator<Item = u8> + Clone,
{
let mut ret = String::new();
format_iter(&mut ret, data).expect("writing into string shouldn't fail");
ret
}
fn format_iter<I, W>(writer: &mut W, data: I) -> Result<(), fmt::Error>
where
I: Iterator<Item = u8> + Clone,
W: fmt::Write,
{
let mut ret = SmallVec::new();
let mut leading_zero_count = 0;
let mut leading_zeroes = true;
// Build string in little endian with 0-58 in place of characters...
for d256 in data {
let mut carry = d256 as usize;
if leading_zeroes && carry == 0 {
leading_zero_count += 1;
} else {
leading_zeroes = false;
}
for ch in ret.iter_mut() {
let new_ch = *ch as usize * 256 + carry;
*ch = (new_ch % 58) as u8;
carry = new_ch / 58;
}
while carry > 0 {
ret.push((carry % 58) as u8);
carry /= 58;
}
}
// ... then reverse it and convert to chars
for _ in 0..leading_zero_count {
ret.push(0);
}
for ch in ret.iter().rev() {
writer.write_char(BASE58_CHARS[*ch as usize] as char)?;
}
Ok(())
}
/// Vector-like object that holds the first 100 elements on the stack. If more space is needed it
/// will be allocated on the heap.
struct SmallVec<T> {
len: usize,
stack: [T; 100],
heap: Vec<T>,
}
impl<T: Default + Copy> SmallVec<T> {
fn new() -> SmallVec<T> { SmallVec { len: 0, stack: [T::default(); 100], heap: Vec::new() } }
fn push(&mut self, val: T) {
if self.len < 100 {
self.stack[self.len] = val;
self.len += 1;
} else {
self.heap.push(val);
}
}
fn iter(&self) -> iter::Chain<slice::Iter<T>, slice::Iter<T>> {
// If len<100 then we just append an empty vec
self.stack[0..self.len].iter().chain(self.heap.iter())
}
fn iter_mut(&mut self) -> iter::Chain<slice::IterMut<T>, slice::IterMut<T>> {
// If len<100 then we just append an empty vec
self.stack[0..self.len].iter_mut().chain(self.heap.iter_mut())
}
}
#[cfg(test)]
mod tests {
use hex::test_hex_unwrap as hex;
use super::*;
#[test]
fn test_base58_encode() {
// Basics
assert_eq!(&encode(&[0][..]), "1");
assert_eq!(&encode(&[1][..]), "2");
assert_eq!(&encode(&[58][..]), "21");
assert_eq!(&encode(&[13, 36][..]), "211");
// Leading zeroes
assert_eq!(&encode(&[0, 13, 36][..]), "1211");
assert_eq!(&encode(&[0, 0, 0, 0, 13, 36][..]), "1111211");
// Long input (>100 bytes => has to use heap)
let res = encode(
"BitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBit\
coinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoinBitcoin"
.as_bytes(),
);
let exp =
"ZqC5ZdfpZRi7fjA8hbhX5pEE96MdH9hEaC1YouxscPtbJF16qVWksHWR4wwvx7MotFcs2ChbJqK8KJ9X\
wZznwWn1JFDhhTmGo9v6GjAVikzCsBWZehu7bm22xL8b5zBR5AsBygYRwbFJsNwNkjpyFuDKwmsUTKvkULCvucPJrN5\
QUdxpGakhqkZFL7RU4yT";
assert_eq!(&res, exp);
// Addresses
let addr = hex!("00f8917303bfa8ef24f292e8fa1419b20460ba064d");
assert_eq!(&encode_check(&addr[..]), "1PfJpZsjreyVrqeoAfabrRwwjQyoSQMmHH");
}
#[test]
fn test_base58_decode() {
// Basics
assert_eq!(decode("1").ok(), Some(vec![0u8]));
assert_eq!(decode("2").ok(), Some(vec![1u8]));
assert_eq!(decode("21").ok(), Some(vec![58u8]));
assert_eq!(decode("211").ok(), Some(vec![13u8, 36]));
// Leading zeroes
assert_eq!(decode("1211").ok(), Some(vec![0u8, 13, 36]));
assert_eq!(decode("111211").ok(), Some(vec![0u8, 0, 0, 13, 36]));
// Addresses
assert_eq!(
decode_check("1PfJpZsjreyVrqeoAfabrRwwjQyoSQMmHH").ok(),
Some(hex!("00f8917303bfa8ef24f292e8fa1419b20460ba064d"))
);
// Non Base58 char.
assert_eq!(decode("ยข").unwrap_err(), Error::BadByte(194));
}
#[test]
fn test_base58_roundtrip() {
let s = "xprv9wTYmMFdV23N2TdNG573QoEsfRrWKQgWeibmLntzniatZvR9BmLnvSxqu53Kw1UmYPxLgboyZQaXwTCg8MSY3H2EU4pWcQDnRnrVA1xe8fs";
let v: Vec<u8> = decode_check(s).unwrap();
assert_eq!(encode_check(&v[..]), s);
assert_eq!(decode_check(&encode_check(&v[..])).ok(), Some(v));
// Check that empty slice passes roundtrip.
assert_eq!(decode_check(&encode_check(&[])), Ok(vec![]));
// Check that `len > 4` is enforced.
assert_eq!(decode_check(&encode(&[1, 2, 3])), Err(Error::TooShort(3)));
}
}