Implement Bluetooth Multiplex.

PiperOrigin-RevId: 651921709

internal/platform/array_blocking_queue.h

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+// Copyright 2024 Google LLC
+//
+// 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
+//
+//     https://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 PLATFORM_PUBLIC_ARRAY_BLOCKING_QUEUE_H_
+#define PLATFORM_PUBLIC_ARRAY_BLOCKING_QUEUE_H_
+
+#include <cstddef>
+#include <optional>
+#include <queue>
+
+#include "internal/platform/condition_variable.h"
+#include "internal/platform/logging.h"
+#include "internal/platform/mutex.h"
+#include "internal/platform/mutex_lock.h"
+
+namespace nearby {
+
+/**
+ * Payload from different services/clients will be put into an
+ * ArrayBlockingQueue before sending to ensure each client has equal chance to
+ * send its data. Since C++ doesn't provide ArrayBlockingQueue as Java, we
+ * implement one here.
+ */
+template <typename T>
+class ArrayBlockingQueue {
+ public:
+  explicit ArrayBlockingQueue(size_t capacity) : capacity_(capacity) {}
+
+  void Put(const T& value) {
+    MutexLock lock(&queue_mutex_);
+    if (queue_.size() >= capacity_) {
+      has_space_.Wait();
+    }
+    queue_.push(value);
+    NEARBY_LOGS(INFO) << "ArrayBlockingQueue::Put()";
+    has_data_.Notify();
+  }
+
+  T Take() {
+    MutexLock lock(&queue_mutex_);
+    if (queue_.empty()) {
+      has_data_.Wait();
+    }
+    T front = queue_.front();
+    queue_.pop();
+    NEARBY_LOGS(INFO) << "ArrayBlockingQueue::Take()";
+    has_space_.Notify();
+    return front;
+  }
+
+  bool TryPut(const T& value) {
+    MutexLock lock(&queue_mutex_);
+    if (queue_.size() < capacity_) {
+      queue_.push(value);
+      has_data_.Notify();
+      return true;
+    }
+    return false;
+  }
+
+  // Returns std::nullopt if the queue is empty.
+  std::optional<T> TryTake() {
+    MutexLock lock(&queue_mutex_);
+    if (!queue_.empty()) {
+      T front = queue_.front();
+      queue_.pop();
+      has_space_.Notify();
+      return front;
+    }
+    return std::nullopt;
+  }
+
+  size_t Size() const {
+    MutexLock lock(&queue_mutex_);
+    return queue_.size();
+  }
+
+  bool Empty() const {
+    MutexLock lock(&queue_mutex_);
+    return queue_.empty();
+  }
+
+ private:
+  std::queue<T> queue_;
+  mutable Mutex queue_mutex_;
+  ConditionVariable has_data_{&queue_mutex_};
+  ConditionVariable has_space_{&queue_mutex_};
+  const size_t capacity_;
+};
+
+}  // namespace nearby
+
+#endif  // PLATFORM_PUBLIC_ARRAY_BLOCKING_QUEUE_H_