1 files changed, 67 insertions, 0 deletions
diff --git a/src/async/async.cpp b/src/async/async.cpp
new file mode 100644
index 0000000..7bcebbb
--- /dev/null
+++ b/src/async/async.cpp
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <vector>
+#include <algorithm>
+#include <mutex>
+#include <chrono>
+#include "async.h"
+#include "util/statics.h"
+
+namespace {
+
+// Todo: Replace when C++ gets an .is_ready().
+bool is_ready(std::future<void> const &future)
+{
+    return future.wait_for(std::chrono::seconds(0)) == std::future_status::ready;
+}
+
+// Holds on to asyncs and waits for them to finish at program exit.
+class AsyncBin
+{
+public:
+    static auto const &get()
+    {
+        /*
+         * Using Static<AsyncBin> to ensure destruction before main() exits, so that lifetimes
+         * of background threads are synchronized with the destruction of statics.
+         */
+        static Inkscape::Util::Static<AsyncBin const> instance;
+        return instance.get();
+    }
+
+    void add(std::future<void> &&future) const
+    {
+        auto g = std::lock_guard(mutables);
+        futures.erase(
+            std::remove_if(futures.begin(), futures.end(), [] (auto const &future) {
+                return is_ready(future);
+            }),
+            futures.end());
+        futures.emplace_back(std::move(future));
+    }
+
+    ~AsyncBin() { drain(); }
+
+private:
+    mutable std::mutex mutables;
+    mutable std::vector<std::future<void>> futures;
+
+    auto grab() const
+    {
+        auto g = std::lock_guard(mutables);
+        return std::move(futures);
+    }
+
+    void drain() const { while (!grab().empty()) {} }
+};
+
+} // namespace
+
+namespace Inkscape {
+namespace Async {
+namespace detail {
+
+void extend(std::future<void> &&future) { AsyncBin::get().add(std::move(future)); }
+
+} // namespace detail
+} // namespace Async
+} // namespace Inkscape