crypto_bigint/uint/encoding/
rlp.rs

1//! Recursive Length Prefix (RLP) encoding support.
2
3use crate::{Encoding, Uint};
4use rlp::{DecoderError, Rlp, RlpStream};
5
6impl<const LIMBS: usize> rlp::Encodable for Uint<LIMBS>
7where
8    Self: Encoding,
9{
10    fn rlp_append(&self, stream: &mut RlpStream) {
11        let bytes = self.to_be_bytes();
12        let mut bytes_stripped = bytes.as_ref();
13
14        while bytes_stripped.first().cloned() == Some(0) {
15            bytes_stripped = &bytes_stripped[1..];
16        }
17
18        stream.encoder().encode_value(bytes_stripped);
19    }
20}
21
22impl<const LIMBS: usize> rlp::Decodable for Uint<LIMBS>
23where
24    Self: Encoding,
25    <Self as Encoding>::Repr: Default,
26{
27    fn decode(rlp: &Rlp<'_>) -> Result<Self, DecoderError> {
28        rlp.decoder().decode_value(|bytes| {
29            if bytes.first().cloned() == Some(0) {
30                Err(DecoderError::RlpInvalidIndirection)
31            } else {
32                let mut repr = <Self as Encoding>::Repr::default();
33                let offset = repr
34                    .as_ref()
35                    .len()
36                    .checked_sub(bytes.len())
37                    .ok_or(DecoderError::RlpIsTooBig)?;
38
39                repr.as_mut()[offset..].copy_from_slice(bytes);
40                Ok(Self::from_be_bytes(repr))
41            }
42        })
43    }
44}
45
46#[cfg(test)]
47#[allow(clippy::unwrap_used)]
48mod tests {
49    use crate::U256;
50    use hex_literal::hex;
51
52    /// U256 test vectors from the `rlp` crate.
53    ///
54    /// <https://github.com/paritytech/parity-common/blob/faad8b6/rlp/tests/tests.rs#L216-L222>
55    const U256_VECTORS: &[(U256, &[u8])] = &[
56        (U256::ZERO, &hex!("80")),
57        (
58            U256::from_be_hex("0000000000000000000000000000000000000000000000000000000001000000"),
59            &hex!("8401000000"),
60        ),
61        (
62            U256::from_be_hex("00000000000000000000000000000000000000000000000000000000ffffffff"),
63            &hex!("84ffffffff"),
64        ),
65        (
66            U256::from_be_hex("8090a0b0c0d0e0f00910203040506077000000000000000100000000000012f0"),
67            &hex!("a08090a0b0c0d0e0f00910203040506077000000000000000100000000000012f0"),
68        ),
69    ];
70
71    #[test]
72    fn round_trip() {
73        for &(uint, expected_bytes) in U256_VECTORS {
74            assert_eq!(rlp::encode(&uint), expected_bytes);
75            assert_eq!(rlp::decode::<U256>(expected_bytes).unwrap(), uint);
76        }
77    }
78}
crypto_bigint/uint/encoding/rlp.rs

crypto_bigint/uint/encoding/
rlp.rs
