Add a triple_buffer class that allows publishing data in a wait-free manner from a real-time thread to another thread.

It's largely inspired from the crate cubeb-coreaudio-rs uses, but ported to
C++.

1 files changed, 67 insertions, 0 deletions

diff --git a/test/test_triple_buffer.cpp b/test/test_triple_buffer.cpp
new file mode 100644
index 0000000..a6e0049
--- /dev/null
+++ b/test/test_triple_buffer.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright © 2022 Mozilla Foundation
+ *
+ * This program is made available under an ISC-style license.  See the
+ * accompanying file LICENSE for details.
+ */
+
+/* cubeb_triple_buffer test  */
+#include "gtest/gtest.h"
+#if !defined(_XOPEN_SOURCE)
+#define _XOPEN_SOURCE 600
+#endif
+#include "cubeb/cubeb.h"
+#include "cubeb_triple_buffer.h"
+#include <atomic>
+#include <math.h>
+#include <memory>
+#include <stdio.h>
+#include <stdlib.h>
+#include <thread>
+
+#include "common.h"
+
+TEST(cubeb, triple_buffer)
+{
+  struct AB {
+    uint64_t a;
+    uint64_t b;
+  };
+  triple_buffer<AB> buffer;
+
+  std::atomic<bool> finished = {false};
+
+  ASSERT_TRUE(!buffer.updated());
+
+  auto t = std::thread([&finished, &buffer] {
+    AB ab;
+    ab.a = 0;
+    ab.b = UINT64_MAX;
+    uint64_t counter = 0;
+    do {
+      buffer.write(ab);
+      ab.a++;
+      ab.b--;
+    } while (counter++ < 1e6 && ab.a <= UINT64_MAX && ab.b != 0);
+    finished.store(true);
+  });
+
+  AB ab;
+  AB old_ab;
+  old_ab.a = 0;
+  old_ab.b = UINT64_MAX;
+
+  // Wait to have at least one value produced.
+  while (!buffer.updated()) {
+  }
+
+  // Check that the values are increasing (resp. descreasing) monotonically.
+  while (!finished) {
+    ab = buffer.read();
+    ASSERT_GE(ab.a, old_ab.a);
+    ASSERT_LE(ab.b, old_ab.b);
+    old_ab = ab;
+  }
+
+  t.join();
+}