Fix #38 - support rust_decimal. (#42)

Author: finnbear

Cargo.toml

@@ -19,6 +19,7 @@ arrayvec = { version = "0.7", default-features = false, optional = true }
 bitcode_derive = { version = "=0.6.5", path = "./bitcode_derive", optional = true }
 bytemuck = { version = "1.14", features = [ "min_const_generics", "must_cast" ] }
 glam = { version = ">=0.21", default-features = false, optional = true }
+rust_decimal = { version = "1.36", default-features = false, optional = true }
 serde = { version = "1.0", default-features = false, features = [ "alloc" ], optional = true }
 time = { version = "0.3", default-features = false, optional = true }
 uuid = { version = "1.10", default-features = false, optional = true }

fuzz/Cargo.toml

@@ -10,8 +10,9 @@ cargo-fuzz = true
 
 [dependencies]
 arrayvec = { version = "0.7", features = ["serde"] }
-bitcode = { path = "..", features = [ "arrayvec", "serde", "time" ] }
+bitcode = { path = "..", features = [ "arrayvec", "rust_decimal", "serde", "time" ] }
 libfuzzer-sys = "0.4"
+rust_decimal = "1.36.0"
 serde = { version ="1.0", features = [ "derive" ] }
 time = { version = "0.3", features = ["serde"]}
 

fuzz/fuzz_targets/fuzz.rs

@@ -10,6 +10,7 @@ use std::fmt::Debug;
 use std::num::NonZeroU32;
 use std::time::Duration;
 use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
+use rust_decimal::Decimal;
 
 #[inline(never)]
 fn test_derive<T: Debug + PartialEq + Encode + DecodeOwned>(data: &[u8]) {
@@ -209,6 +210,7 @@ fuzz_target!(|data: &[u8]| {
         ArrayString<70>,
         ArrayVec<u8, 5>,
         ArrayVec<u8, 70>,
+        Decimal,
         Duration,
         Ipv4Addr,
         Ipv6Addr,

src/ext/mod.rs

@@ -3,6 +3,8 @@ mod arrayvec;
 #[cfg(feature = "glam")]
 #[rustfmt::skip] // Makes impl_struct! calls way longer.
 mod glam;
+#[cfg(feature = "rust_decimal")]
+mod rust_decimal;
 #[cfg(feature = "time")]
 mod time;
 #[cfg(feature = "uuid")]

src/ext/rust_decimal.rs

@@ -0,0 +1,80 @@
+use crate::{
+    convert::{impl_convert, ConvertFrom},
+    int::ranged_int,
+};
+use rust_decimal::Decimal;
+
+type Mantissa = [u8; 12];
+ranged_int!(Scale, u8, 0, Decimal::MAX_SCALE as u8);
+type DecimalEncode = (Mantissa, bool, u8);
+type DecimalDecode = (Mantissa, bool, Scale);
+
+impl ConvertFrom<&Decimal> for DecimalEncode {
+    #[inline(always)]
+    fn convert_from(value: &Decimal) -> Self {
+        let unpacked = value.unpack();
+        let [a0, a1, a2, a3] = unpacked.lo.to_le_bytes();
+        let [b0, b1, b2, b3] = unpacked.mid.to_le_bytes();
+        let [c0, c1, c2, c3] = unpacked.hi.to_le_bytes();
+        (
+            [a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, c3],
+            unpacked.negative,
+            unpacked.scale as u8,
+        )
+    }
+}
+
+impl ConvertFrom<DecimalDecode> for Decimal {
+    #[inline(always)]
+    fn convert_from(value: DecimalDecode) -> Self {
+        let [a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, c3] = value.0;
+        let lo = u32::from_le_bytes([a0, a1, a2, a3]);
+        let mid = u32::from_le_bytes([b0, b1, b2, b3]);
+        let hi = u32::from_le_bytes([c0, c1, c2, c3]);
+        let mut ret = Self::from_parts(lo, mid, hi, false, value.2.into_inner() as u32);
+        ret.set_sign_negative(value.1);
+        ret
+    }
+}
+
+impl_convert!(Decimal, DecimalEncode, DecimalDecode);
+
+#[cfg(test)]
+mod tests {
+    use crate::{decode, encode};
+    use rust_decimal::Decimal;
+    use std::str::FromStr;
+
+    #[test]
+    fn rust_decimal() {
+        assert!(Decimal::MAX_SCALE <= u8::MAX as u32);
+
+        let vs = [
+            Decimal::from(0),
+            Decimal::from_f64_retain(-0f64).unwrap(),
+            Decimal::from(-1),
+            Decimal::from(1) / Decimal::from(2),
+            Decimal::from(1),
+            Decimal::from(999999999999999999u64),
+            Decimal::from_str("3.100").unwrap(),
+        ];
+        for v in vs {
+            let d = decode::<Decimal>(&encode(&v)).unwrap();
+            assert_eq!(d, v);
+            assert_eq!(d.is_sign_negative(), v.is_sign_negative());
+            assert_eq!(d.scale(), v.scale());
+        }
+
+        assert!(crate::decode::<Decimal>(&crate::encode(&([42u8; 12], false, 28u8))).is_ok());
+        assert!(crate::decode::<Decimal>(&crate::encode(&([42u8; 12], false, 29u8))).is_err());
+    }
+
+    use alloc::vec::Vec;
+    fn bench_data() -> Vec<Decimal> {
+        crate::random_data(1000)
+            .into_iter()
+            .map(|(n, s): (i64, u32)| Decimal::new(n, s % (Decimal::MAX_SCALE + 1)))
+            .collect()
+    }
+    crate::bench_encode_decode!(decimal_vec: Vec<_>);
+}

src/int.rs

@@ -150,7 +150,9 @@ macro_rules! ranged_int {
             type Bits = $int;
             #[inline(always)]
             fn is_valid_bit_pattern(bits: &Self::Bits) -> bool {
-                ($lower..=$upper).contains(bits)
+                const LOWER: $int = $lower;
+                const UPPER: $int = $upper;
+                (LOWER..=UPPER).contains(bits)
             }
         }
         impl $type {