feat: add support for fastrlp@0.4

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Support for sqlx @ 0.8 ([#400])
+- Support for fastrlp @ 0.4 ([#401])
 - Added support for [`subtle`](https://docs.rs/subtle) and [`der`](https://docs.rs/der) ([#399])
 
 ### Removed
@@ -21,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 [#399]: https://github.com/recmo/uint/pull/399
 [#400]: https://github.com/recmo/uint/pull/400
+[#401]: https://github.com/recmo/uint/pull/401
 
 ## [1.12.3] - 2024-06-03
 

Cargo.toml

@@ -52,7 +52,10 @@ arbitrary = { version = "1", optional = true, default-features = false }
 ark-ff-03 = { version = "0.3.0", package = "ark-ff", optional = true, default-features = false }
 ark-ff-04 = { version = "0.4.0", package = "ark-ff", optional = true, default-features = false }
 bn-rs = { version = "0.2", optional = true, default-features = true }
-fastrlp = { version = "0.3", optional = true, default-features = false, features = [
+fastrlp-03 = { version = "0.3", package = "fastrlp", optional = true, default-features = false, features = [
+    "alloc",
+] }
+fastrlp-04 = { version = "0.4", package = "fastrlp", optional = true, default-features = false, features = [
     "alloc",
 ] }
 num-bigint = { version = "0.4", optional = true, default-features = false }
@@ -110,7 +113,8 @@ std = [
     "ark-ff-03?/std",
     "ark-ff-04?/std",
     "bytes?/std",
-    "fastrlp?/std",
+    "fastrlp-03?/std",
+    "fastrlp-04?/std",
     "num-bigint?/std",
     "num-integer?/std",
     "num-traits?/std",
@@ -144,7 +148,8 @@ ark-ff-04 = ["dep:ark-ff-04"]
 bn-rs = ["dep:bn-rs", "std"]
 bytemuck = ["dep:bytemuck"]
 der = ["dep:der", "alloc"]                                             # TODO: also have alloc free der impls.
-fastrlp = ["dep:fastrlp", "alloc"]
+fastrlp = ["dep:fastrlp-03", "alloc"]
+fastrlp-04 = ["dep:fastrlp-04", "alloc"]
 num-bigint = ["dep:num-bigint", "alloc"]
 num-integer = ["dep:num-integer", "num-traits", "alloc"]
 num-traits = ["dep:num-traits", "alloc"]

src/support/fastrlp.rs → src/support/fastrlp_03.rs

@@ -4,7 +4,7 @@
 #![cfg_attr(docsrs, doc(cfg(feature = "fastrlp")))]
 
 use crate::Uint;
-use fastrlp::{
+use fastrlp_03::{
     length_of_length, BufMut, Decodable, DecodeError, Encodable, Header, MaxEncodedLen,
     MaxEncodedLenAssoc, EMPTY_STRING_CODE,
 };

src/support/fastrlp_04.rs

@@ -0,0 +1,171 @@
+//! Support for the [`fastrlp`](https://crates.io/crates/fastrlp) crate.
+
+#![cfg(feature = "fastrlp-04")]
+#![cfg_attr(docsrs, doc(cfg(feature = "fastrlp-04")))]
+
+use crate::Uint;
+use fastrlp_04::{
+    length_of_length, BufMut, Decodable, DecodeError, Encodable, Header, MaxEncodedLen,
+    MaxEncodedLenAssoc, EMPTY_STRING_CODE,
+};
+
+const MAX_BITS: usize = 55 * 8;
+
+/// Allows a [`Uint`] to be serialized as RLP.
+///
+/// See <https://ethereum.org/en/developers/docs/data-structures-and-encoding/rlp/>
+impl<const BITS: usize, const LIMBS: usize> Encodable for Uint<BITS, LIMBS> {
+    #[inline]
+    fn length(&self) -> usize {
+        let bits = self.bit_len();
+        if bits <= 7 {
+            1
+        } else {
+            let bytes = (bits + 7) / 8;
+            bytes + length_of_length(bytes)
+        }
+    }
+
+    #[inline]
+    fn encode(&self, out: &mut dyn BufMut) {
+        // fast paths, avoiding allocation due to `to_be_bytes_vec`
+        match LIMBS {
+            0 => return out.put_u8(EMPTY_STRING_CODE),
+            1 => return self.limbs[0].encode(out),
+            #[allow(clippy::cast_lossless)]
+            2 => return (self.limbs[0] as u128 | ((self.limbs[1] as u128) << 64)).encode(out),
+            _ => {}
+        }
+
+        match self.bit_len() {
+            0 => out.put_u8(EMPTY_STRING_CODE),
+            1..=7 => {
+                #[allow(clippy::cast_possible_truncation)] // self < 128
+                out.put_u8(self.limbs[0] as u8);
+            }
+            bits => {
+                // avoid heap allocation in `to_be_bytes_vec`
+                // SAFETY: we don't re-use `copy`
+                #[cfg(target_endian = "little")]
+                let mut copy = *self;
+                #[cfg(target_endian = "little")]
+                let bytes = unsafe { copy.as_le_slice_mut() };
+                #[cfg(target_endian = "little")]
+                bytes.reverse();
+
+                #[cfg(target_endian = "big")]
+                let bytes = self.to_be_bytes_vec();
+
+                let leading_zero_bytes = Self::BYTES - (bits + 7) / 8;
+                let trimmed = &bytes[leading_zero_bytes..];
+                if bits > MAX_BITS {
+                    trimmed.encode(out);
+                } else {
+                    #[allow(clippy::cast_possible_truncation)] // bytes.len() < 56 < 256
+                    out.put_u8(EMPTY_STRING_CODE + trimmed.len() as u8);
+                    out.put_slice(trimmed);
+                }
+            }
+        }
+    }
+}
+
+/// Allows a [`Uint`] to be deserialized from RLP.
+///
+/// See <https://ethereum.org/en/developers/docs/data-structures-and-encoding/rlp/>
+impl<const BITS: usize, const LIMBS: usize> Decodable for Uint<BITS, LIMBS> {
+    #[inline]
+    fn decode(buf: &mut &[u8]) -> Result<Self, DecodeError> {
+        // let bytes = Header::decode_bytes(buf, false)?;
+        let header = Header::decode(buf)?;
+        if header.list {
+            return Err(DecodeError::UnexpectedList);
+        }
+
+        let bytes = &buf[..header.payload_length];
+        *buf = &buf[header.payload_length..];
+
+        // The RLP spec states that deserialized positive integers with leading zeroes
+        // get treated as invalid.
+        //
+        // See:
+        // https://ethereum.org/en/developers/docs/data-structures-and-encoding/rlp/
+        //
+        // To check this, we only need to check if the first byte is zero to make sure
+        // there are no leading zeros
+        if !bytes.is_empty() && bytes[0] == 0 {
+            return Err(DecodeError::LeadingZero);
+        }
+
+        Self::try_from_be_slice(bytes).ok_or(DecodeError::Overflow)
+    }
+}
+
+#[cfg(feature = "generic_const_exprs")]
+unsafe impl<const BITS: usize, const LIMBS: usize>
+    MaxEncodedLen<{ Self::BYTES + length_of_length(Self::BYTES) }> for Uint<BITS, LIMBS>
+{
+}
+
+#[cfg(not(feature = "generic_const_exprs"))]
+const _: () = {
+    crate::const_for!(BITS in [0, 1, 2, 8, 16, 32, 64, 128, 160, 192, 256, 384, 512, 4096] {
+        const LIMBS: usize = crate::nlimbs(BITS);
+        const BYTES: usize = Uint::<BITS, LIMBS>::BYTES;
+        unsafe impl MaxEncodedLen<{ BYTES + length_of_length(BYTES) }> for Uint<BITS, LIMBS> {}
+    });
+};
+
+unsafe impl<const BITS: usize, const LIMBS: usize> MaxEncodedLenAssoc for Uint<BITS, LIMBS> {
+    const LEN: usize = Self::BYTES + length_of_length(Self::BYTES);
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::{
+        aliases::{U0, U256},
+        const_for, nlimbs,
+    };
+    use hex_literal::hex;
+    use proptest::proptest;
+
+    fn encode<T: Encodable>(value: T) -> Vec<u8> {
+        let mut buf = vec![];
+        value.encode(&mut buf);
+        buf
+    }
+
+    #[test]
+    fn test_rlp() {
+        // See <https://github.com/paritytech/parity-common/blob/436cb0827f0e3238ccb80d7d453f756d126c0615/rlp/tests/tests.rs#L214>
+        assert_eq!(encode(U0::from(0))[..], hex!("80"));
+        assert_eq!(encode(U256::from(0))[..], hex!("80"));
+        assert_eq!(encode(U256::from(15))[..], hex!("0f"));
+        assert_eq!(encode(U256::from(1024))[..], hex!("820400"));
+        assert_eq!(encode(U256::from(0x1234_5678))[..], hex!("8412345678"));
+    }
+
+    #[test]
+    fn test_roundtrip() {
+        const_for!(BITS in SIZES {
+            const LIMBS: usize = nlimbs(BITS);
+            proptest!(|(value: Uint<BITS, LIMBS>)| {
+                let serialized = encode(value);
+
+                #[cfg(feature = "rlp")]
+                {
+                    use rlp::Encodable as _;
+                    let serialized_rlp = value.rlp_bytes();
+                    assert_eq!(serialized, serialized_rlp.freeze()[..]);
+                }
+
+                assert_eq!(serialized.len(), value.length());
+                let mut reader = &serialized[..];
+                let deserialized = Uint::decode(&mut reader).unwrap();
+                assert_eq!(reader.len(), 0);
+                assert_eq!(value, deserialized);
+            });
+        });
+    }
+}

src/support/mod.rs

@@ -9,7 +9,8 @@ mod ark_ff_04;
 mod bn_rs;
 mod bytemuck;
 mod der;
-mod fastrlp;
+mod fastrlp_03;
+mod fastrlp_04;
 mod num_bigint;
 mod num_integer;
 mod num_traits;