Optimize array access in ERC1155 (#4300)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Francisco Giordano <fg@frang.io>

contracts/utils/Arrays.sol

@@ -102,4 +102,26 @@ library Arrays {
         }
         return slot.getUint256Slot();
     }
+
+    /**
+     * @dev Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.
+     *
+     * WARNING: Only use if you are certain `pos` is lower than the array length.
+     */
+    function unsafeMemoryAccess(uint256[] memory arr, uint256 pos) internal pure returns (uint256 res) {
+        assembly {
+            res := mload(add(add(arr, 0x20), mul(pos, 0x20)))
+        }
+    }
+
+    /**
+     * @dev Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.
+     *
+     * WARNING: Only use if you are certain `pos` is lower than the array length.
+     */
+    function unsafeMemoryAccess(address[] memory arr, uint256 pos) internal pure returns (address res) {
+        assembly {
+            res := mload(add(add(arr, 0x20), mul(pos, 0x20)))
+        }
+    }
 }