From 5ed4eb72b631bb85be1e0e738904ceec005d0053 Mon Sep 17 00:00:00 2001
From: bcumming <bcumming@cscs.ch>
Date: Tue, 2 Aug 2016 17:15:06 +0200
Subject: [PATCH] add double_buffer type
---
src/util/double_buffer.hpp | 57 ++++++++++++++++++++++++++++++
tests/unit/CMakeLists.txt | 1 +
tests/unit/test_double_buffer.cpp | 58 +++++++++++++++++++++++++++++++
3 files changed, 116 insertions(+)
create mode 100644 src/util/double_buffer.hpp
create mode 100644 tests/unit/test_double_buffer.cpp
diff --git a/src/util/double_buffer.hpp b/src/util/double_buffer.hpp
new file mode 100644
index 00000000..34dceb7f
--- /dev/null
+++ b/src/util/double_buffer.hpp
@@ -0,0 +1,57 @@
+#pragma once
+
+#include <array>
+#include <atomic>
+
+#include <util/debug.hpp>
+
+namespace nest {
+namespace mc {
+namespace util {
+
+template <typename T>
+class double_buffer {
+private:
+ std::atomic<int> index_;
+ std::array<T, 2> buffers_;
+
+ int other_index() {
+ return index_ ? 0 : 1;
+ }
+
+public:
+ using value_type = T;
+
+ double_buffer() :
+ index_(0)
+ {}
+
+ double_buffer(double_buffer&&) = delete;
+ double_buffer(const double_buffer&) = delete;
+ double_buffer& operator=(const double_buffer&) = delete;
+ double_buffer& operator=(double_buffer&&) = delete;
+
+ void exchange() {
+ index_ ^= 1;
+ }
+
+ value_type& get() {
+ return buffers_[index_];
+ }
+
+ const value_type& get() const {
+ return buffers_[index_];
+ }
+
+ value_type& other() {
+ return buffers_[other_index()];
+ }
+
+ const value_type& other() const {
+ return buffers_[other_index()];
+ }
+};
+
+} // namespace util
+} // namespace mc
+} // namespace nest
diff --git a/tests/unit/CMakeLists.txt b/tests/unit/CMakeLists.txt
index a3a2d553..81976dd2 100644
--- a/tests/unit/CMakeLists.txt
+++ b/tests/unit/CMakeLists.txt
@@ -11,6 +11,7 @@ set(HEADERS
set(TEST_SOURCES
# unit tests
test_algorithms.cpp
+ test_double_buffer.cpp
test_cell.cpp
test_compartments.cpp
test_event_queue.cpp
diff --git a/tests/unit/test_double_buffer.cpp b/tests/unit/test_double_buffer.cpp
new file mode 100644
index 00000000..1689cc2f
--- /dev/null
+++ b/tests/unit/test_double_buffer.cpp
@@ -0,0 +1,58 @@
+#include "gtest.h"
+
+#include <util/double_buffer.hpp>
+
+// not much to test here: just test that values passed into the constructor
+// are correctly stored in members
+TEST(double_buffer, exchange_and_get)
+{
+ using namespace nest::mc::util;
+
+ double_buffer<int> buf;
+
+ buf.get() = 2134;
+ buf.exchange();
+ buf.get() = 8990;
+ buf.exchange();
+
+ EXPECT_EQ(buf.get(), 2134);
+ EXPECT_EQ(buf.other(), 8990);
+ buf.exchange();
+ EXPECT_EQ(buf.get(), 8990);
+ EXPECT_EQ(buf.other(), 2134);
+ buf.exchange();
+ EXPECT_EQ(buf.get(), 2134);
+ EXPECT_EQ(buf.other(), 8990);
+}
+
+TEST(double_buffer, assign_get_other)
+{
+ using namespace nest::mc::util;
+
+ double_buffer<std::string> buf;
+
+ buf.get() = "1";
+ buf.other() = "2";
+
+ EXPECT_EQ(buf.get(), "1");
+ EXPECT_EQ(buf.other(), "2");
+}
+
+TEST(double_buffer, non_pod)
+{
+ using namespace nest::mc::util;
+
+ double_buffer<std::string> buf;
+
+ buf.get() = "1";
+ buf.other() = "2";
+
+ EXPECT_EQ(buf.get(), "1");
+ EXPECT_EQ(buf.other(), "2");
+ buf.exchange();
+ EXPECT_EQ(buf.get(), "2");
+ EXPECT_EQ(buf.other(), "1");
+ buf.exchange();
+ EXPECT_EQ(buf.get(), "1");
+ EXPECT_EQ(buf.other(), "2");
+}
--
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