1 files changed, 140 insertions, 0 deletions
diff --git a/Firestore/core/src/firebase/firestore/util/async_queue.cc b/Firestore/core/src/firebase/firestore/util/async_queue.cc
new file mode 100644
index 0000000..71f5cc5
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/util/async_queue.cc
@@ -0,0 +1,140 @@
+/*
+ * Copyright 2018 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.
+ */
+
+#include "Firestore/core/src/firebase/firestore/util/async_queue.h"
+
+#include <utility>
+
+#include "Firestore/core/src/firebase/firestore/util/firebase_assert.h"
+#include "absl/memory/memory.h"
+
+namespace firebase {
+namespace firestore {
+namespace util {
+
+using internal::Executor;
+
+AsyncQueue::AsyncQueue(std::unique_ptr<Executor> executor)
+    : executor_{std::move(executor)} {
+  is_operation_in_progress_ = false;
+}
+
+void AsyncQueue::VerifyIsCurrentExecutor() const {
+  FIREBASE_ASSERT_MESSAGE(
+      executor_->IsCurrentExecutor(),
+      "Expected to be called by the executor associated with this queue "
+      "(expected executor: '%s', actual executor: '%s')",
+      executor_->Name().c_str(), executor_->CurrentExecutorName().c_str());
+}
+
+void AsyncQueue::VerifyIsCurrentQueue() const {
+  VerifyIsCurrentExecutor();
+  FIREBASE_ASSERT_MESSAGE(
+      is_operation_in_progress_,
+      "VerifyIsCurrentQueue called when no operation is executing "
+      "(expected executor: '%s', actual executor: '%s')",
+      executor_->Name().c_str(), executor_->CurrentExecutorName().c_str());
+}
+
+void AsyncQueue::ExecuteBlocking(const Operation& operation) {
+  VerifyIsCurrentExecutor();
+  FIREBASE_ASSERT_MESSAGE(!is_operation_in_progress_,
+                          "ExecuteBlocking may not be called "
+                          "before the previous operation finishes executing");
+
+  is_operation_in_progress_ = true;
+  operation();
+  is_operation_in_progress_ = false;
+}
+
+void AsyncQueue::Enqueue(const Operation& operation) {
+  VerifySequentialOrder();
+  EnqueueRelaxed(operation);
+}
+
+void AsyncQueue::EnqueueRelaxed(const Operation& operation) {
+  executor_->Execute(Wrap(operation));
+}
+
+DelayedOperation AsyncQueue::EnqueueAfterDelay(const Milliseconds delay,
+                                               const TimerId timer_id,
+                                               const Operation& operation) {
+  VerifyIsCurrentExecutor();
+
+  // While not necessarily harmful, we currently don't expect to have multiple
+  // callbacks with the same timer_id in the queue, so defensively reject
+  // them.
+  FIREBASE_ASSERT_MESSAGE(
+      !IsScheduled(timer_id),
+      "Attempted to schedule multiple operations with id %d", timer_id);
+
+  Executor::TaggedOperation tagged{static_cast<int>(timer_id), Wrap(operation)};
+  return executor_->Schedule(delay, std::move(tagged));
+}
+
+AsyncQueue::Operation AsyncQueue::Wrap(const Operation& operation) {
+  // Decorator pattern: wrap `operation` into a call to `ExecuteBlocking` to
+  // ensure that it doesn't spawn any nested operations.
+
+  // Note: can't move `operation` into lambda until C++14.
+  return [this, operation] { ExecuteBlocking(operation); };
+}
+
+void AsyncQueue::VerifySequentialOrder() const {
+  // This is the inverse of `VerifyIsCurrentQueue`.
+  FIREBASE_ASSERT_MESSAGE(
+      !is_operation_in_progress_ || !executor_->IsCurrentExecutor(),
+      "Enforcing sequential order failed: currently executing operations "
+      "cannot enqueue more operations "
+      "(this queue's executor: '%s', current executor: '%s')",
+      executor_->Name().c_str(), executor_->CurrentExecutorName().c_str());
+}
+
+// Test-only functions
+
+void AsyncQueue::EnqueueBlocking(const Operation& operation) {
+  VerifySequentialOrder();
+  executor_->ExecuteBlocking(Wrap(operation));
+}
+
+bool AsyncQueue::IsScheduled(const TimerId timer_id) const {
+  return executor_->IsScheduled(static_cast<int>(timer_id));
+}
+
+void AsyncQueue::RunScheduledOperationsUntil(const TimerId last_timer_id) {
+  FIREBASE_ASSERT_MESSAGE(
+      !executor_->IsCurrentExecutor(),
+      "RunScheduledOperationsUntil must not be called on the queue");
+
+  executor_->ExecuteBlocking([this, last_timer_id] {
+    FIREBASE_ASSERT_MESSAGE(
+        last_timer_id == TimerId::All || IsScheduled(last_timer_id),
+        "Attempted to run scheduled operations until missing timer id: %d",
+        last_timer_id);
+
+    for (auto next = executor_->PopFromSchedule(); next.has_value();
+         next = executor_->PopFromSchedule()) {
+      next->operation();
+      if (next->tag == static_cast<int>(last_timer_id)) {
+        break;
+      }
+    }
+  });
+}
+
+}  // namespace util
+}  // namespace firestore
+}  // namespace firebase