feat: getters for ctc extradata (#204)

* feat: getters for ctc extradata

* contracts: lint fix

* contracts: fix build

packages/contracts/contracts/optimistic-ethereum/OVM/chain/OVM_CanonicalTransactionChain.sol

@@ -158,10 +158,42 @@ contract OVM_CanonicalTransactionChain is iOVM_CanonicalTransactionChain, Lib_Ad
             uint40
         )
     {
-        (, uint40 nextQueueIndex,,) = _getBatchExtraData();
+        (,uint40 nextQueueIndex,,) = _getBatchExtraData();
         return nextQueueIndex;
     }
 
+    /**
+     * Returns the timestamp of the last transaction.
+     * @return Timestamp for the last transaction.
+     */
+    function getLastTimestamp()
+        override
+        public
+        view
+        returns (
+            uint40
+        )
+    {
+        (,,uint40 lastTimestamp,) = _getBatchExtraData();
+        return lastTimestamp;
+    }
+
+    /**
+     * Returns the blocknumber of the last transaction.
+     * @return Blocknumber for the last transaction.
+     */
+    function getLastBlockNumber()
+        override
+        public
+        view
+        returns (
+            uint40
+        )
+    {
+        (,,,uint40 lastBlockNumber) = _getBatchExtraData();
+        return lastBlockNumber;
+    }
+
     /**
      * Gets the queue element at a particular index.
      * @param _index Index of the queue element to access.

packages/contracts/contracts/optimistic-ethereum/iOVM/chain/iOVM_CanonicalTransactionChain.sol

@@ -133,6 +133,28 @@ interface iOVM_CanonicalTransactionChain {
             Lib_OVMCodec.QueueElement memory _element
         );
 
+    /**
+     * Returns the timestamp of the last transaction.
+     * @return Timestamp for the last transaction.
+     */
+    function getLastTimestamp()
+        external
+        view
+        returns (
+            uint40
+        );
+
+    /**
+     * Returns the blocknumber of the last transaction.
+     * @return Blocknumber for the last transaction.
+     */
+    function getLastBlockNumber()
+        external
+        view
+        returns (
+            uint40
+        );
+
     /**
      * Get the number of queue elements which have not yet been included.
      * @return Number of pending queue elements.