Port FSTListenSequence (#2322)

Author: Greg Soltis

Firestore/Source/Core/FSTListenSequence.h

@@ -21,7 +21,6 @@
 #include <utility>
 
 #import "FIRFirestoreErrors.h"
-#import "Firestore/Source/Core/FSTListenSequence.h"
 #import "Firestore/Source/Local/FSTLRUGarbageCollector.h"
 #import "Firestore/Source/Local/FSTLevelDBMutationQueue.h"
 #import "Firestore/Source/Remote/FSTSerializerBeta.h"
@@ -35,6 +34,7 @@
 #include "Firestore/core/src/firebase/firestore/local/leveldb_remote_document_cache.h"
 #include "Firestore/core/src/firebase/firestore/local/leveldb_transaction.h"
 #include "Firestore/core/src/firebase/firestore/local/leveldb_util.h"
+#include "Firestore/core/src/firebase/firestore/local/listen_sequence.h"
 #include "Firestore/core/src/firebase/firestore/local/reference_set.h"
 #include "Firestore/core/src/firebase/firestore/local/remote_document_cache.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
@@ -66,6 +66,7 @@
 using firebase::firestore::local::LevelDbQueryCache;
 using firebase::firestore::local::LevelDbRemoteDocumentCache;
 using firebase::firestore::local::LevelDbTransaction;
+using firebase::firestore::local::ListenSequence;
 using firebase::firestore::local::LruParams;
 using firebase::firestore::local::ReferenceSet;
 using firebase::firestore::local::RemoteDocumentCache;
@@ -119,7 +120,8 @@ @implementation FSTLevelDBLRUDelegate {
   __weak FSTLevelDB *_db;
   ReferenceSet *_additionalReferences;
   ListenSequenceNumber _currentSequenceNumber;
-  FSTListenSequence *_listenSequence;
+  // PORTING NOTE: doesn't need to be a pointer once this class is ported to C++.
+  std::unique_ptr<ListenSequence> _listenSequence;
 }
 
 - (instancetype)initWithPersistence:(FSTLevelDB *)persistence lruParams:(LruParams)lruParams {
@@ -133,13 +135,13 @@ - (instancetype)initWithPersistence:(FSTLevelDB *)persistence lruParams:(LruPara
 
 - (void)start {
   ListenSequenceNumber highestSequenceNumber = _db.queryCache->highest_listen_sequence_number();
-  _listenSequence = [[FSTListenSequence alloc] initStartingAfter:highestSequenceNumber];
+  _listenSequence = absl::make_unique<ListenSequence>(highestSequenceNumber);
 }
 
 - (void)transactionWillStart {
   HARD_ASSERT(_currentSequenceNumber == kFSTListenSequenceNumberInvalid,
               "Previous sequence number is still in effect");
-  _currentSequenceNumber = [_listenSequence next];
+  _currentSequenceNumber = _listenSequence->Next();
 }
 
 - (void)transactionWillCommit {

Firestore/Source/Core/FSTListenSequence.mm

@@ -21,7 +21,6 @@
 #include <utility>
 
 #import "FIRTimestamp.h"
-#import "Firestore/Source/Core/FSTListenSequence.h"
 #import "Firestore/Source/Core/FSTQuery.h"
 #import "Firestore/Source/Local/FSTLRUGarbageCollector.h"
 #import "Firestore/Source/Local/FSTLocalDocumentsView.h"

Firestore/Source/Local/FSTLevelDB.mm

@@ -21,11 +21,11 @@
 #include <unordered_set>
 #include <vector>
 
-#import "Firestore/Source/Core/FSTListenSequence.h"
 #import "Firestore/Source/Local/FSTMemoryMutationQueue.h"
 #include "absl/memory/memory.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
+#include "Firestore/core/src/firebase/firestore/local/listen_sequence.h"
 #include "Firestore/core/src/firebase/firestore/local/memory_query_cache.h"
 #include "Firestore/core/src/firebase/firestore/local/memory_remote_document_cache.h"
 #include "Firestore/core/src/firebase/firestore/local/reference_set.h"
@@ -34,6 +34,7 @@
 
 using firebase::firestore::auth::HashUser;
 using firebase::firestore::auth::User;
+using firebase::firestore::local::ListenSequence;
 using firebase::firestore::local::LruParams;
 using firebase::firestore::local::MemoryQueryCache;
 using firebase::firestore::local::MemoryRemoteDocumentCache;
@@ -161,7 +162,8 @@ @implementation FSTMemoryLRUReferenceDelegate {
   std::unordered_map<DocumentKey, ListenSequenceNumber, DocumentKeyHash> _sequenceNumbers;
   ReferenceSet *_additionalReferences;
   FSTLRUGarbageCollector *_gc;
-  FSTListenSequence *_listenSequence;
+  // PORTING NOTE: when this class is ported to C++, this does not need to be a pointer
+  std::unique_ptr<ListenSequence> _listenSequence;
   ListenSequenceNumber _currentSequenceNumber;
   FSTLocalSerializer *_serializer;
 }
@@ -176,7 +178,7 @@ - (instancetype)initWithPersistence:(FSTMemoryPersistence *)persistence
     // Theoretically this is always 0, since this is all in-memory...
     ListenSequenceNumber highestSequenceNumber =
         _persistence.queryCache->highest_listen_sequence_number();
-    _listenSequence = [[FSTListenSequence alloc] initStartingAfter:highestSequenceNumber];
+    _listenSequence = absl::make_unique<ListenSequence>(highestSequenceNumber);
     _serializer = serializer;
   }
   return self;
@@ -210,7 +212,7 @@ - (void)limboDocumentUpdated:(const DocumentKey &)key {
 }
 
 - (void)startTransaction:(absl::string_view)label {
-  _currentSequenceNumber = [_listenSequence next];
+  _currentSequenceNumber = _listenSequence->Next();
 }
 
 - (void)commitTransaction {

Firestore/Source/Local/FSTLocalStore.mm

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2019 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_LOCAL_LISTEN_SEQUENCE_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_LOCAL_LISTEN_SEQUENCE_H_
+
+#include "Firestore/core/src/firebase/firestore/model/types.h"
+
+namespace firebase {
+namespace firestore {
+namespace local {
+
+/**
+ * ListenSequence is a monotonic sequence. It is initialized with a minimum
+ * value to exceed. All subsequent calls to next will return increasing values.
+ */
+class ListenSequence {
+ public:
+  explicit ListenSequence(model::ListenSequenceNumber starting_after)
+      : previous_sequence_number_(starting_after) {
+  }
+
+  model::ListenSequenceNumber Next() {
+    previous_sequence_number_++;
+    return previous_sequence_number_;
+  }
+
+ private:
+  model::ListenSequenceNumber previous_sequence_number_;
+};
+
+}  // namespace local
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_LOCAL_LISTEN_SEQUENCE_H_