fully refactored, all tests pass

Author: Bengt Lofgren

solana/programs/matching-engine/src/fallback/processor/prepare_order_response.rs

@@ -226,9 +226,9 @@ pub fn prepare_order_response_cctp_shim(
     let receive_message_args = data.to_receive_message_args();
     let finalized_vaa_message = data.finalized_vaa_message;
     // Load accounts
+    let fast_market_order_account_data = fast_market_order.data.borrow();
     let fast_market_order_zero_copy =
-        FastMarketOrderState::try_deserialize(&mut &fast_market_order.data.borrow()[..])
-            .map(Box::new)?;
+        FastMarketOrderState::try_read(&fast_market_order_account_data[..])?;
     // Create pdas for addresses that need to be created
     // Check the prepared order response account is valid
     // TODO: Pass the digest so it isn't recomputed

solana/programs/matching-engine/src/state/fast_market_order.rs

@@ -1,4 +1,5 @@
 use anchor_lang::prelude::*;
+use anchor_lang::Discriminator;
 use solana_program::keccak;
 
 /// An account that represents a fast market order vaa. It is created by the signer of the transaction, and owned by the matching engine program.
@@ -139,4 +140,18 @@ impl FastMarketOrder {
             .try_into()
             .unwrap()
     }
+
+    /// Read from an account info
+    pub fn try_read(data: &[u8]) -> Result<&Self> {
+        if data.len() < 8 {
+            return Err(ErrorCode::AccountDiscriminatorNotFound.into());
+        }
+        let discriminator: [u8; 8] = data[0..8].try_into().unwrap();
+        if discriminator != Self::discriminator() {
+            return Err(ErrorCode::AccountDiscriminatorMismatch.into());
+        }
+        let byte_muck_data = &data[8..];
+        let fast_market_order = bytemuck::from_bytes::<Self>(byte_muck_data);
+        Ok(fast_market_order)
+    }
 }