From 6367268b255ff6abd45d8c8eca23296301d15c0c Mon Sep 17 00:00:00 2001
From: Jonathan Lifflander <jliffla@sandia.gov>
Date: Tue, 6 Sep 2022 15:11:37 -0700
Subject: [PATCH] #1950: utils: implement circular buffer with fixed size

---
 src/vt/utils/container/circular_buffer.h | 116 +++++++++++++++++++++++
 1 file changed, 116 insertions(+)
 create mode 100644 src/vt/utils/container/circular_buffer.h

diff --git a/src/vt/utils/container/circular_buffer.h b/src/vt/utils/container/circular_buffer.h
new file mode 100644
index 0000000000..9e79570da3
--- /dev/null
+++ b/src/vt/utils/container/circular_buffer.h
@@ -0,0 +1,116 @@
+/*
+//@HEADER
+// *****************************************************************************
+//
+//                              circular_buffer.h
+//                       DARMA/vt => Virtual Transport
+//
+// Copyright 2019-2021 National Technology & Engineering Solutions of Sandia, LLC
+// (NTESS). Under the terms of Contract DE-NA0003525 with NTESS, the U.S.
+// Government retains certain rights in this software.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+//
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+//
+// * Neither the name of the copyright holder nor the names of its
+//   contributors may be used to endorse or promote products derived from this
+//   software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Questions? Contact darma@sandia.gov
+//
+// *****************************************************************************
+//@HEADER
+*/
+
+#if !defined INCLUDED_VT_UTILS_CONTAINER_CIRCULAR_BUFFER_H
+#define INCLUDED_VT_UTILS_CONTAINER_CIRCULAR_BUFFER_H
+
+#include "vt/config.h"
+
+namespace vt { namespace util { namespace container {
+
+template <typename T, int size>
+struct CircularBuffer {
+
+  CircularBuffer() = default;
+
+private:
+  int getNextEntry() const {
+    int next_entry = head_ + 1;
+    if (next_entry == size) {
+      next_entry = 0;
+    }
+    return next_entry;
+  }
+
+public:
+  template <typename... Args>
+  void emplace(Args&&... args) {
+    int const next_entry = getNextEntry();
+    elms_[head_] = T{std::forward<Args>(args)...};
+    head_ = next_entry;
+  }
+
+  void push(T&& t) {
+    int const next_entry = getNextEntry();
+    elms_[head_] = std::move(t);
+    head_ = next_entry;
+  }
+
+  void push(T const& t) {
+    int const next_entry = getNextEntry();
+    elms_[head_] = t;
+    head_ = next_entry;
+  }
+
+  T pop() {
+    T elm = std::move(elms_[tail_]);
+    ++tail_;
+    if (tail_ == size) {
+      tail_ = 0;
+    }
+    return elm;
+  }
+
+  int numFree() const {
+    if (head_ == tail_) {
+      return size - 1;
+    } else if (head_ < tail_) {
+      return tail_ - head_ - 1;
+    } else {
+      return size + tail_ - head_ - 1;
+    }
+  }
+
+  bool empty() const { return head_ == tail_; }
+  bool full() const { return numFree() == 0; }
+  int len() const { return size - 1 - numFree(); }
+
+private:
+  int head_ = 0;
+  int tail_ = 0;
+  std::array<T, size> elms_;
+};
+
+}}} /* end namespace vt::util::container */
+
+#endif /*INCLUDED_VT_UTILS_CONTAINER_CIRCULAR_BUFFER_H*/