Add immutable get_extension, and clean up mod

token/program-2022/src/extension/memo_transfer/mod.rs

@@ -25,8 +25,8 @@ impl Extension for MemoTransfer {
 }
 
 /// Determine if a memo is required for transfers into this account
-pub fn memo_required(mut account_state: StateWithExtensionsMut<Account>) -> bool {
-    if let Ok(extension) = account_state.get_extension_mut::<MemoTransfer>() {
+pub fn memo_required(account_state: &StateWithExtensionsMut<Account>) -> bool {
+    if let Ok(extension) = account_state.get_extension::<MemoTransfer>() {
         return extension.require_incoming_transfer_memos.into();
     }
     false

token/program-2022/src/extension/mod.rs

@@ -434,11 +434,30 @@ impl<'data, S: BaseState> StateWithExtensionsMut<'data, S> {
         }
     }
 
-    /// Unpack a portion of the TLV data as the desired type
+    /// Unpack a portion of the TLV data as the desired type that allows modifying the type
     pub fn get_extension_mut<V: Extension>(&mut self) -> Result<&mut V, ProgramError> {
         self.init_or_get_extension(false)
     }
 
+    /// Unpack a portion of the TLV data as the desired type
+    pub fn get_extension<V: Extension>(&self) -> Result<&V, ProgramError> {
+        if V::TYPE.get_account_type() != S::ACCOUNT_TYPE {
+            return Err(ProgramError::InvalidAccountData);
+        }
+        let TlvIndices {
+            type_start,
+            length_start,
+            value_start,
+        } = get_extension_indices::<V>(self.tlv_data, false)?;
+
+        if self.tlv_data[type_start..].len() < V::TYPE.get_tlv_len() {
+            return Err(ProgramError::InvalidAccountData);
+        }
+        let length = pod_from_bytes::<Length>(&self.tlv_data[length_start..value_start])?;
+        let value_end = value_start.saturating_add(usize::from(*length));
+        pod_from_bytes::<V>(&self.tlv_data[value_start..value_end])
+    }
+
     /// Packs base state data into the base data portion
     pub fn pack_base(&mut self) {
         S::pack_into_slice(&self.base, self.base_data);

token/program-2022/src/processor.rs

@@ -8,7 +8,7 @@ use {
             confidential_transfer::{self, ConfidentialTransferAccount},
             default_account_state::{self, DefaultAccountState},
             immutable_owner::ImmutableOwner,
-            memo_transfer::{self, MemoTransfer},
+            memo_transfer::{self, memo_required},
             mint_close_authority::MintCloseAuthority,
             reallocate,
             transfer_fee::{self, TransferFeeAmount, TransferFeeConfig},
@@ -373,10 +373,8 @@ impl Processor {
             return Err(TokenError::MintMismatch.into());
         }
 
-        if let Ok(extension) = dest_account.get_extension_mut::<MemoTransfer>() {
-            if extension.require_incoming_transfer_memos.into() {
-                // TODO: use get_processed_instructions syscall to check for memo
-            }
+        if memo_required(&dest_account) {
+            // TODO: use get_processed_instructions syscall to check for memo
         }
 
         source_account.base.amount = source_account