From bac3da61644515f05663789b122554dc77549286 Mon Sep 17 00:00:00 2001
From: Luca Muscariello <lumuscar+fdio@cisco.com>
Date: Thu, 17 Jan 2019 13:47:57 +0100
Subject: This is the first commit of the hicn project

Change-Id: I6f2544ad9b9f8891c88cc4bcce3cf19bd3cc863f
Signed-off-by: Luca Muscariello <lumuscar+fdio@cisco.com>
---
 .../src/hicn/transport/utils/ring_buffer.h         | 129 +++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100755 libtransport/src/hicn/transport/utils/ring_buffer.h

(limited to 'libtransport/src/hicn/transport/utils/ring_buffer.h')

diff --git a/libtransport/src/hicn/transport/utils/ring_buffer.h b/libtransport/src/hicn/transport/utils/ring_buffer.h
new file mode 100755
index 000000000..52bcd81c4
--- /dev/null
+++ b/libtransport/src/hicn/transport/utils/ring_buffer.h
@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2017-2019 Cisco and/or its affiliates.
+ * 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.
+ */
+
+#pragma once
+
+#include <atomic>
+#include <cstddef>
+
+namespace utils {
+
+/**
+ * NOTE: Single consumer single producer ring buffer
+ */
+template <typename Element, std::size_t Size>
+class CircularFifo {
+ public:
+  enum { Capacity = Size + 1 };
+
+  CircularFifo() : tail_(0), head_(0), size_(0) {}
+  virtual ~CircularFifo() {}
+
+  bool push(const Element& item);
+  bool push(Element&& item);
+  bool pop(Element& item);
+
+  bool wasEmpty() const;
+  bool wasFull() const;
+  bool isLockFree() const;
+  std::size_t size() const;
+
+ private:
+  std::size_t increment(std::size_t idx) const;
+  std::atomic<std::size_t> tail_;  // tail(input) index
+  Element array_[Capacity];
+  std::atomic<std::size_t> head_;  // head(output) index
+  std::atomic<std::size_t> size_;
+};
+
+template <typename Element, std::size_t Size>
+bool CircularFifo<Element, Size>::push(const Element& item) {
+  const auto current_tail = tail_.load(std::memory_order_relaxed);
+  const auto next_tail = increment(current_tail);
+  if (next_tail != head_.load(std::memory_order_acquire)) {
+    array_[current_tail] = item;
+    tail_.store(next_tail, std::memory_order_release);
+    size_++;
+    return true;
+  }
+
+  // full queue
+  return false;
+}
+
+/**
+ * Push by move
+ */
+template <typename Element, std::size_t Size>
+bool CircularFifo<Element, Size>::push(Element&& item) {
+  const auto current_tail = tail_.load(std::memory_order_relaxed);
+  const auto next_tail = increment(current_tail);
+  if (next_tail != head_.load(std::memory_order_acquire)) {
+    array_[current_tail] = std::move(item);
+    tail_.store(next_tail, std::memory_order_release);
+    size_++;
+    return true;
+  }
+
+  // full queue
+  return false;
+}
+
+// Pop by Consumer can only update the head
+// (load with relaxed, store with release)
+// the tail must be accessed with at least acquire
+template <typename Element, std::size_t Size>
+bool CircularFifo<Element, Size>::pop(Element& item) {
+  const auto current_head = head_.load(std::memory_order_relaxed);
+  if (current_head == tail_.load(std::memory_order_acquire)) {
+    return false;  // empty queue
+  }
+
+  item = std::move(array_[current_head]);
+  head_.store(increment(current_head), std::memory_order_release);
+  size_--;
+  return true;
+}
+
+template <typename Element, std::size_t Size>
+bool CircularFifo<Element, Size>::wasEmpty() const {
+  // snapshot with acceptance of that this comparison operation is not atomic
+  return (head_.load() == tail_.load());
+}
+
+// snapshot with acceptance that this comparison is not atomic
+template <typename Element, std::size_t Size>
+bool CircularFifo<Element, Size>::wasFull() const {
+  const auto next_tail =
+      increment(tail_.load());  // acquire, we dont know who call
+  return (next_tail == head_.load());
+}
+
+template <typename Element, std::size_t Size>
+bool CircularFifo<Element, Size>::isLockFree() const {
+  return (tail_.is_lock_free() && head_.is_lock_free());
+}
+
+template <typename Element, std::size_t Size>
+std::size_t CircularFifo<Element, Size>::increment(std::size_t idx) const {
+  return (idx + 1) % Capacity;
+}
+
+template <typename Element, std::size_t Size>
+std::size_t CircularFifo<Element, Size>::size() const {
+  return size_.load(std::memory_order_relaxed);
+}
+
+}  // namespace utils
\ No newline at end of file
-- 
cgit 1.2.3-korg