bs58/alphabet.rs
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//! Support for configurable alphabets
use core::fmt;
/// Prepared Alphabet for
/// [`EncodeBuilder::with_alphabet`](crate::encode::EncodeBuilder::with_alphabet) and
/// [`DecodeBuilder::with_alphabet`](crate::decode::DecodeBuilder::with_alphabet).
#[derive(Clone, Copy)]
pub struct Alphabet {
pub(crate) encode: [u8; 58],
pub(crate) decode: [u8; 128],
}
/// Errors that could occur when preparing a Base58 alphabet.
#[non_exhaustive]
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum Error {
/// The alphabet contained a duplicate character at at least 2 indexes.
DuplicateCharacter {
/// The duplicate character encountered.
character: char,
/// The first index the character was seen at.
first: usize,
/// The second index the character was seen at.
second: usize,
},
/// The alphabet contained a multi-byte (or non-utf8) character.
NonAsciiCharacter {
/// The index at which the non-ASCII character was seen.
index: usize,
},
}
impl Alphabet {
/// Bitcoin's alphabet as defined in their Base58Check encoding.
///
/// See <https://en.bitcoin.it/wiki/Base58Check_encoding#Base58_symbol_chart>
pub const BITCOIN: &'static Self =
&Self::new_unwrap(b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz");
/// Monero's alphabet as defined in this forum post.
///
/// See <https://forum.getmonero.org/4/academic-and-technical/221/creating-a-standard-for-physical-coins>
pub const MONERO: &'static Self =
&Self::new_unwrap(b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz");
/// Ripple's alphabet as defined in their wiki.
///
/// See <https://wiki.ripple.com/Encodings>
pub const RIPPLE: &'static Self =
&Self::new_unwrap(b"rpshnaf39wBUDNEGHJKLM4PQRST7VWXYZ2bcdeCg65jkm8oFqi1tuvAxyz");
/// Flickr's alphabet for creating short urls from photo ids.
///
/// See <https://www.flickr.com/groups/api/discuss/72157616713786392/>
pub const FLICKR: &'static Self =
&Self::new_unwrap(b"123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ");
/// The default alphabet used if none is given. Currently is the
/// [`BITCOIN`](Self::BITCOIN) alphabet.
pub const DEFAULT: &'static Self = Self::BITCOIN;
/// Create prepared alphabet, checks that the alphabet is pure ASCII and that there are no
/// duplicate characters, which would result in inconsistent encoding/decoding
///
/// ```rust
/// let alpha = bs58::Alphabet::new(
/// b" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXY"
/// )?;
///
/// let decoded = bs58::decode("he11owor1d")
/// .with_alphabet(bs58::Alphabet::RIPPLE)
/// .into_vec()?;
/// let encoded = bs58::encode(decoded)
/// .with_alphabet(&alpha)
/// .into_string();
///
/// assert_eq!("#ERRN)N RD", encoded);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
/// ## Errors
///
/// ### Duplicate Character
///
/// ```rust
/// let alpha = b"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
/// assert_eq!(
/// bs58::alphabet::Error::DuplicateCharacter { character: 'a', first: 0, second: 1 },
/// bs58::Alphabet::new(alpha).unwrap_err());
/// ```
///
/// ### Non-ASCII Character
///
/// ```rust
/// let mut alpha = *b"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
/// alpha[1] = 255;
/// assert_eq!(
/// bs58::alphabet::Error::NonAsciiCharacter { index: 1 },
/// bs58::Alphabet::new(&alpha).unwrap_err());
/// ```
pub const fn new(base: &[u8; 58]) -> Result<Self, Error> {
let mut encode = [0x00; 58];
let mut decode = [0xFF; 128];
let mut i = 0;
while i < encode.len() {
if base[i] >= 128 {
return Err(Error::NonAsciiCharacter { index: i });
}
if decode[base[i] as usize] != 0xFF {
return Err(Error::DuplicateCharacter {
character: base[i] as char,
first: decode[base[i] as usize] as usize,
second: i,
});
}
encode[i] = base[i];
decode[base[i] as usize] = i as u8;
i += 1;
}
Ok(Self { encode, decode })
}
/// Same as [`Self::new`], but gives a panic instead of an [`Err`] on bad input.
///
/// Intended to support usage in `const` context until [`Result::unwrap`] is able to be called.
///
/// ```rust
/// const ALPHA: &'static bs58::Alphabet = &bs58::Alphabet::new_unwrap(
/// b" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXY"
/// );
///
/// let decoded = bs58::decode("he11owor1d")
/// .with_alphabet(bs58::Alphabet::RIPPLE)
/// .into_vec()?;
/// let encoded = bs58::encode(decoded)
/// .with_alphabet(ALPHA)
/// .into_string();
///
/// assert_eq!("#ERRN)N RD", encoded);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// If your alphabet is inconsistent then this will fail to compile in a `const` context:
///
/// ```compile_fail
/// const _: &'static bs58::Alphabet = &bs58::Alphabet::new_unwrap(
/// b"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
/// );
/// ```
pub const fn new_unwrap(base: &[u8; 58]) -> Self {
let result = Self::new(base);
#[allow(unconditional_panic)] // https://github.com/rust-lang/rust/issues/78803
[][match result {
Ok(alphabet) => return alphabet,
Err(_) => 0,
}]
}
}
impl fmt::Debug for Alphabet {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if let Ok(s) = core::str::from_utf8(&self.encode) {
f.debug_tuple("Alphabet").field(&s).finish()
} else {
unreachable!()
}
}
}
#[cfg(feature = "std")]
impl std::error::Error for Error {}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
Error::DuplicateCharacter {
character,
first,
second,
} => write!(
f,
"alphabet contained a duplicate character `{}` at indexes {} and {}",
character, first, second,
),
Error::NonAsciiCharacter { index } => {
write!(f, "alphabet contained a non-ascii character at {}", index)
}
}
}
}
// Force evaluation of the associated constants to make sure they don't error
const _: () = {
let _ = Alphabet::BITCOIN;
let _ = Alphabet::MONERO;
let _ = Alphabet::RIPPLE;
let _ = Alphabet::FLICKR;
let _ = Alphabet::DEFAULT;
};
#[test]
#[should_panic]
fn test_new_unwrap_does_panic() {
Alphabet::new_unwrap(b"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
}