Simplified the Behavior object and partially removed the path for applying non-serialized transactions. (#142)

libs/VersionedStorage-cpp/include/Microsoft/MixedReality/Sharing/VersionedStorage/Behavior.h

@@ -83,16 +83,6 @@ class Behavior {
   // Frees pages previously allocated with AllocateZeroedPages.
   virtual void FreePages(void* address) noexcept = 0;
 
-  // Locks the mutex that restricts concurrent modifications of the storage
-  // where necessary.
-  // This is customizable for the cases where the storage blobs are located in
-  // shared memory and modified by multiple processes (in which case the
-  // implementation can use a cross-process OS mutex).
-  virtual void LockWriterMutex() noexcept = 0;
-
-  // Unlocks the mutex that restricts all modifications of the storage.
-  virtual void UnlockWriterMutex() noexcept = 0;
-
   // Serializes the key associated with the provided handle and returns the
   // number of written bytes.
   // The serialized data doesn't have to contain this size, as it will be saved

libs/VersionedStorage-cpp/include/Microsoft/MixedReality/Sharing/VersionedStorage/Storage.h

@@ -60,22 +60,18 @@ class Storage {
   // Applies the provided transaction and increments the version of the storage
   // (unless it failed to allocate memory for the transaction, see all possible
   // outcomes above).
-  // The operation may call LockWriterMutex()/UnlockWriterMutex() on the
-  // Behavior object, but the callers should not rely on this.
-  // Note that the transactions are generally not reusable, and the state of the
-  // provided object can be irreversibly changed regardless of the success of
-  // the operation.
-  [[nodiscard]] TransactionResult ApplyTransaction(
-      TransactionView& transaction) noexcept;
-
   [[nodiscard]] TransactionResult ApplyTransaction(
       std::string_view serialized_transaction) noexcept;
 
   const auto& behavior() const noexcept { return behavior_; }
 
  private:
+  [[nodiscard]] TransactionResult ApplyTransaction(
+      TransactionView& transaction) noexcept;
+
   std::shared_ptr<Behavior> behavior_;
   Snapshot latest_snapshot_;
+  std::mutex writer_mutex_;
   mutable std::mutex latest_snapshot_reader_mutex_;
 };
 

libs/VersionedStorage-cpp/src/Storage.cpp

@@ -642,18 +642,6 @@ class TransactionApplicator {
   size_t extra_blocks_count_{0};
 };
 
-class WriterMutexGuard {
- public:
-  explicit WriterMutexGuard(Behavior& behavior) noexcept : behavior_{behavior} {
-    behavior.LockWriterMutex();
-  }
-
-  ~WriterMutexGuard() noexcept { behavior_.UnlockWriterMutex(); }
-
- private:
-  Behavior& behavior_;
-};
-
 }  // namespace
 }  // namespace Microsoft::MixedReality::Sharing::VersionedStorage::Detail
 
@@ -676,7 +664,7 @@ Snapshot Storage::GetSnapshot() const noexcept {
 
 Storage::TransactionResult Storage::ApplyTransaction(
     TransactionView& transaction) noexcept {
-  auto writer_mutex_guard = Detail::WriterMutexGuard(*behavior_);
+  auto writer_mutex_lock = std::lock_guard{writer_mutex_};
   // No need to lock latest_snapshot_reader_mutex_ here to perform the read
   // since only the writer thread can modify the latest_snapshot_ field, and
   // this method is called by the writer thread.

libs/VersionedStorage-cpp/tests/TestBehavior.cpp

@@ -147,14 +147,6 @@ void TestBehavior::FreePages(void* address) noexcept {
   Platform::FreePages(address);
 }
 
-void TestBehavior::LockWriterMutex() noexcept {
-  writer_mutex_.lock();
-}
-
-void TestBehavior::UnlockWriterMutex() noexcept {
-  writer_mutex_.unlock();
-}
-
 size_t TestBehavior::Serialize(KeyHandle handle,
                                std::vector<std::byte>& byte_stream) {
   size_t size = byte_stream.size();

libs/VersionedStorage-cpp/tests/TestBehavior.h

@@ -49,9 +49,6 @@ class TestBehavior : public Behavior {
   void* AllocateZeroedPages(size_t pages_count) noexcept override;
   void FreePages(void* address) noexcept override;
 
-  void LockWriterMutex() noexcept override;
-  void UnlockWriterMutex() noexcept override;
-
   size_t Serialize(KeyHandle handle,
                    std::vector<std::byte>& byte_stream) override;