1 files changed, 54 insertions, 0 deletions

diff --git a/src/core/hle/service/hid/ring_lifo.h b/src/core/hle/service/hid/ring_lifo.h
new file mode 100644
index 000000000..44c20d967
--- /dev/null
+++ b/src/core/hle/service/hid/ring_lifo.h
@@ -0,0 +1,54 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included
+
+#pragma once
+
+#include <array>
+
+#include "common/common_types.h"
+
+namespace Service::HID {
+
+template <typename State>
+struct AtomicStorage {
+    s64 sampling_number;
+    State state;
+};
+
+template <typename State, std::size_t max_buffer_size>
+struct Lifo {
+    s64 timestamp{};
+    s64 total_buffer_count = static_cast<s64>(max_buffer_size);
+    s64 buffer_tail{};
+    s64 buffer_count{};
+    std::array<AtomicStorage<State>, max_buffer_size> entries{};
+
+    const AtomicStorage<State>& ReadCurrentEntry() const {
+        return entries[buffer_tail];
+    }
+
+    const AtomicStorage<State>& ReadPreviousEntry() const {
+        return entries[GetPreviousEntryIndex()];
+    }
+
+    std::size_t GetPreviousEntryIndex() const {
+        return static_cast<size_t>((buffer_tail + total_buffer_count - 1) % total_buffer_count);
+    }
+
+    std::size_t GetNextEntryIndex() const {
+        return static_cast<size_t>((buffer_tail + 1) % total_buffer_count);
+    }
+
+    void WriteNextEntry(const State& new_state) {
+        if (buffer_count < total_buffer_count - 1) {
+            buffer_count++;
+        }
+        buffer_tail = GetNextEntryIndex();
+        const auto& previous_entry = ReadPreviousEntry();
+        entries[buffer_tail].sampling_number = previous_entry.sampling_number + 1;
+        entries[buffer_tail].state = new_state;
+    }
+};
+
+} // namespace Service::HID