Optimisations in the sequencer inbox

src/bridge/AbsBridge.sol

@@ -14,11 +14,15 @@ import {
     NotSequencerInbox,
     NotOutbox,
     InvalidOutboxSet,
-    BadSequencerMessageNumber
+    BadSequencerMessageNumber,
+    EmptyDelayedMessagesRead,
+    DelayedBackwards,
+    DelayedTooFar
 } from "../libraries/Error.sol";
 import "./IBridge.sol";
 import "./Messages.sol";
 import "../libraries/DelegateCallAware.sol";
+import "./ISequencerInbox.sol";
 
 import {L1MessageType_batchPostingReport} from "../libraries/MessageTypes.sol";
 
@@ -55,8 +59,25 @@ abstract contract AbsBridge is Initializable, DelegateCallAware, IBridge {
 
     uint256 public override sequencerReportedSubMessageCount;
 
+    uint256 public totalDelayedMessagesRead;
+
     address internal constant EMPTY_ACTIVEOUTBOX = address(type(uint160).max);
 
+    event SequencerBatchDelivered(
+        uint256 indexed batchSequenceNumber,
+        bytes32 indexed beforeAcc,
+        bytes32 indexed afterAcc,
+        bytes32 delayedAcc,
+        uint256 afterDelayedMessagesRead,
+        ICommon.TimeBounds timeBounds,
+        ICommon.BatchDataLocation dataLocation
+    );
+
+    function postUpgradeInit() external onlyDelegated onlyProxyOwner {
+        totalDelayedMessagesRead = ISequencerInbox(sequencerInbox).totalDelayedMessagesRead();
+        if (totalDelayedMessagesRead == 0) revert EmptyDelayedMessagesRead();
+    }
+
     modifier onlyRollupOrOwner() {
         if (msg.sender != address(rollup)) {
             address rollupOwner = rollup.owner();
@@ -101,7 +122,9 @@ abstract contract AbsBridge is Initializable, DelegateCallAware, IBridge {
         bytes32 dataHash,
         uint256 afterDelayedMessagesRead,
         uint256 prevMessageCount,
-        uint256 newMessageCount
+        uint256 newMessageCount,
+        ICommon.TimeBounds memory timeBounds,
+        ICommon.BatchDataLocation batchDataLocation
     )
         external
         onlySequencerInbox
@@ -119,6 +142,9 @@ abstract contract AbsBridge is Initializable, DelegateCallAware, IBridge {
         ) {
             revert BadSequencerMessageNumber(sequencerReportedSubMessageCount, prevMessageCount);
         }
+        if (afterDelayedMessagesRead > delayedInboxAccs.length) revert DelayedTooFar();
+        if (afterDelayedMessagesRead < totalDelayedMessagesRead) revert DelayedBackwards();
+
         sequencerReportedSubMessageCount = newMessageCount;
         seqMessageIndex = sequencerInboxAccs.length;
         if (sequencerInboxAccs.length > 0) {
@@ -129,6 +155,17 @@ abstract contract AbsBridge is Initializable, DelegateCallAware, IBridge {
         }
         acc = keccak256(abi.encodePacked(beforeAcc, dataHash, delayedAcc));
         sequencerInboxAccs.push(acc);
+        totalDelayedMessagesRead = afterDelayedMessagesRead;
+
+        emit SequencerBatchDelivered(
+            seqMessageIndex,
+            beforeAcc,
+            acc,
+            delayedAcc,
+            afterDelayedMessagesRead,
+            timeBounds,
+            batchDataLocation
+        );
     }
 
     /// @inheritdoc IBridge
@@ -304,5 +341,5 @@ abstract contract AbsBridge is Initializable, DelegateCallAware, IBridge {
      * variables without shifting down storage in the inheritance chain.
      * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
      */
-    uint256[40] private __gap;
+    uint256[39] private __gap;
 }

src/bridge/IBridge.sol

@@ -6,6 +6,7 @@
 pragma solidity >=0.6.9 <0.9.0;
 
 import "./IOwnable.sol";
+import "./ICommon.sol";
 
 interface IBridge {
     event MessageDelivered(
@@ -66,13 +67,17 @@ interface IBridge {
 
     function sequencerMessageCount() external view returns (uint256);
 
+    function totalDelayedMessagesRead() external view returns (uint256);
+
     // ---------- onlySequencerInbox functions ----------
 
     function enqueueSequencerMessage(
         bytes32 dataHash,
         uint256 afterDelayedMessagesRead,
         uint256 prevMessageCount,
-        uint256 newMessageCount
+        uint256 newMessageCount,
+        ICommon.TimeBounds memory timeBounds,
+        ICommon.BatchDataLocation dataLocation
     )
         external
         returns (

src/bridge/ICommon.sol

@@ -0,0 +1,21 @@
+// Copyright 2021-2022, Offchain Labs, Inc.
+// For license information, see https://github.com/OffchainLabs/nitro-contracts/blob/main/LICENSE
+// SPDX-License-Identifier: BUSL-1.1
+
+// solhint-disable-next-line compiler-version
+pragma solidity >=0.6.9 <0.9.0;
+
+interface ICommon {
+    enum BatchDataLocation {
+        TxInput,
+        SeparateBatchEvent,
+        NoData
+    }
+
+    struct TimeBounds {
+        uint64 minTimestamp;
+        uint64 maxTimestamp;
+        uint64 minBlockNumber;
+        uint64 maxBlockNumber;
+    }
+}

src/bridge/ISequencerInbox.sol

@@ -9,6 +9,7 @@ pragma experimental ABIEncoderV2;
 import "../libraries/IGasRefunder.sol";
 import "./IDelayedMessageProvider.sol";
 import "./IBridge.sol";
+import "./ICommon.sol";
 
 interface ISequencerInbox is IDelayedMessageProvider {
     /// @notice The maximum amount of time variatin between a message being posted on the L1 and being executed on the L2
@@ -23,29 +24,6 @@ interface ISequencerInbox is IDelayedMessageProvider {
         uint256 futureSeconds;
     }
 
-    struct TimeBounds {
-        uint64 minTimestamp;
-        uint64 maxTimestamp;
-        uint64 minBlockNumber;
-        uint64 maxBlockNumber;
-    }
-
-    enum BatchDataLocation {
-        TxInput,
-        SeparateBatchEvent,
-        NoData
-    }
-
-    event SequencerBatchDelivered(
-        uint256 indexed batchSequenceNumber,
-        bytes32 indexed beforeAcc,
-        bytes32 indexed afterAcc,
-        bytes32 delayedAcc,
-        uint256 afterDelayedMessagesRead,
-        TimeBounds timeBounds,
-        BatchDataLocation dataLocation
-    );
-
     event OwnerFunctionCalled(uint256 indexed id);
 
     /// @dev a separate event that emits batch data when this isn't easily accessible in the tx.input
@@ -57,6 +35,8 @@ interface ISequencerInbox is IDelayedMessageProvider {
     /// @dev a keyset was invalidated
     event InvalidateKeyset(bytes32 indexed keysetHash);
 
+    /// @notice The total number of delated messages read in the bridge
+    /// @dev    We surface this here for backwards compatibility
     function totalDelayedMessagesRead() external view returns (uint256);
 
     function bridge() external view returns (IBridge);