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|
//! Implements the slightly odd "base32" encoding that's used in Nix.
//!
//! Nix uses a custom alphabet. Contrary to other implementations (RFC4648),
//! encoding to "nix base32" doesn't use any padding, and reads in characters
//! in reverse order.
//!
//! This is also the main reason why `data_encoding::Encoding` can't be used
//! directly, but this module aims to provide a similar interface (with some
//! methods omitted).
use data_encoding::{DecodeError, Encoding, Specification};
use lazy_static::lazy_static;
/// Nixbase32Encoding wraps a data_encoding::Encoding internally.
/// We can't use it directly, as nix also reads in characters in reverse order.
pub struct Nixbase32Encoding {
encoding: Encoding,
}
lazy_static! {
/// Returns a Nixbase32Encoding providing some functions seen on a data_encoding::Encoding.
pub static ref NIXBASE32: Nixbase32Encoding = nixbase32_encoding();
}
/// Populates the Nixbase32Encoding struct with a data_encoding::Encoding,
/// using the nixbase32 alphabet and config.
fn nixbase32_encoding() -> Nixbase32Encoding {
let mut spec = Specification::new();
spec.symbols.push_str("0123456789abcdfghijklmnpqrsvwxyz");
Nixbase32Encoding {
encoding: spec.encoding().unwrap(),
}
}
impl Nixbase32Encoding {
/// Returns encoded input
pub fn encode(&self, input: &[u8]) -> String {
// Reverse the input, reading in the bytes in reverse order.
let reversed: Vec<u8> = input.iter().cloned().rev().collect();
self.encoding.encode(&reversed)
}
/// Returns decoded input
/// Check [data_encoding::Encoding::encode] for the error cases.
pub fn decode(&self, input: &[u8]) -> Result<Vec<u8>, DecodeError> {
// Decode first, then reverse the bytes of the output.
let mut output = self.encoding.decode(&input)?;
output.reverse();
Ok(output)
}
/// Returns the decoded length of an input of length len.
/// Check [data_encoding::Encoding::decode_len] for the error cases.
pub fn decode_len(&self, len: usize) -> Result<usize, DecodeError> {
self.encoding.decode_len(len)
}
/// Returns the encoded length of an input of length len
pub fn encode_len(&self, len: usize) -> usize {
self.encoding.encode_len(len)
}
}
#[cfg(test)]
mod tests {
use crate::nixbase32::NIXBASE32;
use test_case::test_case;
#[test_case("", vec![] ; "empty bytes")]
// FUTUREWORK: b/235
// this seems to encode to 3w?
// #[test_case("0z", vec![0x1f]; "one byte")]
#[test_case("00bgd045z0d4icpbc2yyz4gx48ak44la", vec![
0x8a, 0x12, 0x32, 0x15, 0x22, 0xfd, 0x91, 0xef, 0xbd, 0x60, 0xeb, 0xb2, 0x48, 0x1a,
0xf8, 0x85, 0x80, 0xf6, 0x16, 0x00]; "nixpath")]
fn encode(enc: &str, dec: Vec<u8>) {
assert_eq!(enc, NIXBASE32.encode(&dec));
}
#[test_case("", Some(vec![]) ; "empty bytes")]
// FUTUREWORK: b/235
// this seems to require spec.check_trailing_bits and still fails?
// #[test_case("0z", Some(vec![0x1f]); "one byte")]
#[test_case("00bgd045z0d4icpbc2yyz4gx48ak44la", Some(vec![
0x8a, 0x12, 0x32, 0x15, 0x22, 0xfd, 0x91, 0xef, 0xbd, 0x60, 0xeb, 0xb2, 0x48, 0x1a,
0xf8, 0x85, 0x80, 0xf6, 0x16, 0x00]); "nixpath")]
// this is invalid encoding, because it encodes 10 1-bytes, so the carry
// would be 2 1-bytes
#[test_case("zz", None; "invalid encoding-1")]
// this is an even more specific example - it'd decode as 00000000 11
// FUTUREWORK: b/235
// #[test_case("c0", None; "invalid encoding-2")]
fn decode(enc: &str, dec: Option<Vec<u8>>) {
match dec {
Some(dec) => {
// The decode needs to match what's passed in dec
assert_eq!(dec, NIXBASE32.decode(enc.as_bytes()).unwrap());
}
None => {
// the decode needs to be an error
assert_eq!(true, NIXBASE32.decode(enc.as_bytes()).is_err());
}
}
}
#[test]
fn encode_len() {
assert_eq!(NIXBASE32.encode_len(20), 32)
}
#[test]
fn decode_len() {
assert_eq!(NIXBASE32.decode_len(32).unwrap(), 20)
}
}
|
