Add a RAII-friendly DI wrapper for driver instances

1 files changed, 54 insertions, 0 deletions

diff --git a/src/drivers/include/driver_cache.hpp b/src/drivers/include/driver_cache.hpp
new file mode 100644
index 00000000..c56ebc3f
--- /dev/null
+++ b/src/drivers/include/driver_cache.hpp
@@ -0,0 +1,54 @@
+#pragma once
+
+#include <memory>
+#include <mutex>
+
+#include "dac.hpp"
+#include "display.hpp"
+#include "gpio_expander.hpp"
+#include "storage.hpp"
+#include "touchwheel.hpp"
+
+namespace drivers {
+
+class DriverCache {
+ private:
+  std::unique_ptr<GpioExpander> gpios_;
+  std::weak_ptr<AudioDac> dac_;
+  std::weak_ptr<Display> display_;
+  std::weak_ptr<SdStorage> storage_;
+  std::weak_ptr<TouchWheel> touchwheel_;
+  // TODO(jacqueline): Haptics, samd
+
+  std::mutex mutex_;
+
+  template <typename T, typename F>
+  auto Acquire(std::weak_ptr<T> ptr, F factory) -> std::shared_ptr<T> {
+    std::shared_ptr<T> acquired = ptr.lock();
+    if (acquired) {
+      return acquired;
+    }
+
+    std::lock_guard<std::mutex> lock(mutex_);
+
+    acquired = ptr.lock();
+    if (acquired) {
+      return acquired;
+    }
+    acquired.reset(factory());
+    ptr = acquired;
+    return acquired;
+  }
+
+ public:
+  DriverCache();
+  ~DriverCache();
+
+  auto AcquireGpios() -> GpioExpander*;
+  auto AcquireDac() -> std::shared_ptr<AudioDac>;
+  auto AcquireDisplay() -> std::shared_ptr<Display>;
+  auto AcquireStorage() -> std::shared_ptr<SdStorage>;
+  auto AcquireTouchWheel() -> std::shared_ptr<TouchWheel>;
+};
+
+}  // namespace drivers