feat: add Bytes31 type

starknet-core/src/types/bytes31.rs

@@ -0,0 +1,74 @@
+use crate::types::Felt;
+
+pub const BYTES31_UPPER_BOUND: Felt = Felt::from_raw([
+    18446744062762287109,
+    20123647,
+    18446744073709514624,
+    576460566199926936,
+]);
+
+/// A 31 byte array primitive used mostly for [`ByteArray`].
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Bytes31(Felt);
+
+mod errors {
+    use core::fmt::{Display, Formatter, Result};
+
+    #[derive(Debug)]
+    pub struct FromFieldElementError;
+
+    #[cfg(feature = "std")]
+    impl std::error::Error for FromFieldElementError {}
+
+    impl Display for FromFieldElementError {
+        fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+            write!(f, "Felt value out of range for Bytes31")
+        }
+    }
+}
+pub use errors::FromFieldElementError;
+
+impl From<Bytes31> for Felt {
+    fn from(value: Bytes31) -> Self {
+        value.0
+    }
+}
+
+impl TryFrom<Felt> for Bytes31 {
+    type Error = FromFieldElementError;
+
+    fn try_from(value: Felt) -> Result<Self, Self::Error> {
+        if value < BYTES31_UPPER_BOUND {
+            Ok(Self(value))
+        } else {
+            Err(FromFieldElementError)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Bytes31, Felt, FromFieldElementError, BYTES31_UPPER_BOUND};
+
+    #[test]
+    #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
+    fn test_bytes31_from_felt_out_of_range() {
+        match Bytes31::try_from(Felt::MAX) {
+            Err(FromFieldElementError) => {}
+            _ => {
+                panic!("Expected Bytes31::try_from(Felt::MAX) to return Err(FromFieldElementError)")
+            }
+        }
+    }
+
+    #[test]
+    #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
+    fn test_bytes31_from_felt() {
+        let expected_felt = BYTES31_UPPER_BOUND - Felt::ONE;
+
+        match Bytes31::try_from(expected_felt) {
+            Ok(bytes31) => assert_eq!(Felt::from(bytes31), expected_felt),
+            _ => panic!("Expected Bytes31 from Felt to be valid"),
+        }
+    }
+}

starknet-core/src/types/mod.rs

@@ -56,6 +56,9 @@ pub use execution_result::ExecutionResult;
 mod receipt_block;
 pub use receipt_block::ReceiptBlock;
 
+mod bytes31;
+pub use bytes31::Bytes31;
+
 mod msg;
 pub use msg::MsgToL2;