5 files changed, 295 insertions, 0 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 47418006b..c0d068376 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -547,6 +547,8 @@ add_library(core STATIC
     hle/service/vi/vi_u.h
     hle/service/wlan/wlan.cpp
     hle/service/wlan/wlan.h
+    host_timing.cpp
+    host_timing.h
     loader/deconstructed_rom_directory.cpp
     loader/deconstructed_rom_directory.h
     loader/elf.cpp
diff --git a/src/core/core_timing_util.cpp b/src/core/core_timing_util.cpp
index de50d3b14..f42666b4d 100644
--- a/src/core/core_timing_util.cpp
+++ b/src/core/core_timing_util.cpp
@@ -49,6 +49,11 @@ s64 nsToCycles(std::chrono::nanoseconds ns) {
     return (Hardware::BASE_CLOCK_RATE * ns.count()) / 1000000000;
 }
 
+u64 nsToClockCycles(std::chrono::nanoseconds ns) {
+    const u128 temporal = Common::Multiply64Into128(ns.count(), CNTFREQ);
+    return Common::Divide128On32(temporal, 1000000000).first;
+}
+
 u64 CpuCyclesToClockCycles(u64 ticks) {
     const u128 temporal = Common::Multiply64Into128(ticks, Hardware::CNTFREQ);
     return Common::Divide128On32(temporal, static_cast<u32>(Hardware::BASE_CLOCK_RATE)).first;
diff --git a/src/core/core_timing_util.h b/src/core/core_timing_util.h
index addc72b19..65fb7368b 100644
--- a/src/core/core_timing_util.h
+++ b/src/core/core_timing_util.h
@@ -13,6 +13,7 @@ namespace Core::Timing {
 s64 msToCycles(std::chrono::milliseconds ms);
 s64 usToCycles(std::chrono::microseconds us);
 s64 nsToCycles(std::chrono::nanoseconds ns);
+u64 nsToClockCycles(std::chrono::nanoseconds ns);
 
 inline std::chrono::milliseconds CyclesToMs(s64 cycles) {
     return std::chrono::milliseconds(cycles * 1000 / Hardware::BASE_CLOCK_RATE);
diff --git a/src/core/host_timing.cpp b/src/core/host_timing.cpp
new file mode 100644
index 000000000..c02f571c6
--- /dev/null
+++ b/src/core/host_timing.cpp
@@ -0,0 +1,161 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "core/host_timing.h"
+
+#include <algorithm>
+#include <mutex>
+#include <string>
+#include <tuple>
+
+#include "common/assert.h"
+#include "common/thread.h"
+#include "core/core_timing_util.h"
+
+namespace Core::HostTiming {
+
+std::shared_ptr<EventType> CreateEvent(std::string name, TimedCallback&& callback) {
+    return std::make_shared<EventType>(std::move(callback), std::move(name));
+}
+
+struct CoreTiming::Event {
+    u64 time;
+    u64 fifo_order;
+    u64 userdata;
+    std::weak_ptr<EventType> type;
+
+    // Sort by time, unless the times are the same, in which case sort by
+    // the order added to the queue
+    friend bool operator>(const Event& left, const Event& right) {
+        return std::tie(left.time, left.fifo_order) > std::tie(right.time, right.fifo_order);
+    }
+
+    friend bool operator<(const Event& left, const Event& right) {
+        return std::tie(left.time, left.fifo_order) < std::tie(right.time, right.fifo_order);
+    }
+};
+
+CoreTiming::CoreTiming() = default;
+CoreTiming::~CoreTiming() = default;
+
+void CoreTiming::ThreadEntry(CoreTiming& instance) {
+    instance.Advance();
+}
+
+void CoreTiming::Initialize() {
+    event_fifo_id = 0;
+    const auto empty_timed_callback = [](u64, s64) {};
+    ev_lost = CreateEvent("_lost_event", empty_timed_callback);
+    start_time = std::chrono::system_clock::now();
+    timer_thread = std::make_unique<std::thread>(ThreadEntry, std::ref(*this));
+}
+
+void CoreTiming::Shutdown() {
+    std::unique_lock<std::mutex> guard(inner_mutex);
+    shutting_down = true;
+    if (!is_set) {
+        is_set = true;
+        condvar.notify_one();
+    }
+    inner_mutex.unlock();
+    timer_thread->join();
+    ClearPendingEvents();
+}
+
+void CoreTiming::ScheduleEvent(s64 ns_into_future, const std::shared_ptr<EventType>& event_type,
+                               u64 userdata) {
+    std::lock_guard guard{inner_mutex};
+    const u64 timeout = static_cast<u64>(GetGlobalTimeNs().count() + ns_into_future);
+
+    event_queue.emplace_back(Event{timeout, event_fifo_id++, userdata, event_type});
+
+    std::push_heap(event_queue.begin(), event_queue.end(), std::greater<>());
+    if (!is_set) {
+        is_set = true;
+        condvar.notify_one();
+    }
+}
+
+void CoreTiming::UnscheduleEvent(const std::shared_ptr<EventType>& event_type, u64 userdata) {
+    std::lock_guard guard{inner_mutex};
+
+    const auto itr = std::remove_if(event_queue.begin(), event_queue.end(), [&](const Event& e) {
+        return e.type.lock().get() == event_type.get() && e.userdata == userdata;
+    });
+
+    // Removing random items breaks the invariant so we have to re-establish it.
+    if (itr != event_queue.end()) {
+        event_queue.erase(itr, event_queue.end());
+        std::make_heap(event_queue.begin(), event_queue.end(), std::greater<>());
+    }
+}
+
+u64 CoreTiming::GetCPUTicks() const {
+    std::chrono::nanoseconds time_now = GetGlobalTimeNs();
+    return Core::Timing::nsToCycles(time_now);
+}
+
+u64 CoreTiming::GetClockTicks() const {
+    std::chrono::nanoseconds time_now = GetGlobalTimeNs();
+    return Core::Timing::nsToClockCycles(time_now);
+}
+
+void CoreTiming::ClearPendingEvents() {
+    event_queue.clear();
+}
+
+void CoreTiming::RemoveEvent(const std::shared_ptr<EventType>& event_type) {
+    std::lock_guard guard{inner_mutex};
+
+    const auto itr = std::remove_if(event_queue.begin(), event_queue.end(), [&](const Event& e) {
+        return e.type.lock().get() == event_type.get();
+    });
+
+    // Removing random items breaks the invariant so we have to re-establish it.
+    if (itr != event_queue.end()) {
+        event_queue.erase(itr, event_queue.end());
+        std::make_heap(event_queue.begin(), event_queue.end(), std::greater<>());
+    }
+}
+
+void CoreTiming::Advance() {
+    while (true) {
+        std::unique_lock<std::mutex> guard(inner_mutex);
+
+        global_timer = GetGlobalTimeNs().count();
+
+        while (!event_queue.empty() && event_queue.front().time <= global_timer) {
+            Event evt = std::move(event_queue.front());
+            std::pop_heap(event_queue.begin(), event_queue.end(), std::greater<>());
+            event_queue.pop_back();
+            inner_mutex.unlock();
+
+            if (auto event_type{evt.type.lock()}) {
+                event_type->callback(evt.userdata, global_timer - evt.time);
+            }
+
+            inner_mutex.lock();
+        }
+        auto next_time = std::chrono::nanoseconds(event_queue.front().time - global_timer);
+        condvar.wait_for(guard, next_time, [this] { return is_set; });
+        is_set = false;
+        if (shutting_down) {
+            break;
+        }
+    }
+}
+
+std::chrono::nanoseconds CoreTiming::GetGlobalTimeNs() const {
+    sys_time_point current = std::chrono::system_clock::now();
+    auto elapsed = current - start_time;
+    return std::chrono::duration_cast<std::chrono::nanoseconds>(elapsed);
+}
+
+std::chrono::microseconds CoreTiming::GetGlobalTimeUs() const {
+    sys_time_point current = std::chrono::system_clock::now();
+    auto elapsed = current - start_time;
+    return std::chrono::duration_cast<std::chrono::microseconds>(elapsed);
+}
+
+} // namespace Core::Timing
diff --git a/src/core/host_timing.h b/src/core/host_timing.h
new file mode 100644
index 000000000..a3a32e087
--- /dev/null
+++ b/src/core/host_timing.h
@@ -0,0 +1,126 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <chrono>
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <optional>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include "common/common_types.h"
+#include "common/threadsafe_queue.h"
+
+namespace Core::HostTiming {
+
+/// A callback that may be scheduled for a particular core timing event.
+using TimedCallback = std::function<void(u64 userdata, s64 cycles_late)>;
+using sys_time_point = std::chrono::time_point<std::chrono::system_clock>;
+
+/// Contains the characteristics of a particular event.
+struct EventType {
+    EventType(TimedCallback&& callback, std::string&& name)
+        : callback{std::move(callback)}, name{std::move(name)} {}
+
+    /// The event's callback function.
+    TimedCallback callback;
+    /// A pointer to the name of the event.
+    const std::string name;
+};
+
+/**
+ * This is a system to schedule events into the emulated machine's future. Time is measured
+ * in main CPU clock cycles.
+ *
+ * To schedule an event, you first have to register its type. This is where you pass in the
+ * callback. You then schedule events using the type id you get back.
+ *
+ * The int cyclesLate that the callbacks get is how many cycles late it was.
+ * So to schedule a new event on a regular basis:
+ * inside callback:
+ *   ScheduleEvent(periodInCycles - cyclesLate, callback, "whatever")
+ */
+class CoreTiming {
+public:
+    CoreTiming();
+    ~CoreTiming();
+
+    CoreTiming(const CoreTiming&) = delete;
+    CoreTiming(CoreTiming&&) = delete;
+
+    CoreTiming& operator=(const CoreTiming&) = delete;
+    CoreTiming& operator=(CoreTiming&&) = delete;
+
+    /// CoreTiming begins at the boundary of timing slice -1. An initial call to Advance() is
+    /// required to end slice - 1 and start slice 0 before the first cycle of code is executed.
+    void Initialize();
+
+    /// Tears down all timing related functionality.
+    void Shutdown();
+
+    /// Schedules an event in core timing
+    void ScheduleEvent(s64 ns_into_future, const std::shared_ptr<EventType>& event_type,
+                       u64 userdata = 0);
+
+    void UnscheduleEvent(const std::shared_ptr<EventType>& event_type, u64 userdata);
+
+    /// We only permit one event of each type in the queue at a time.
+    void RemoveEvent(const std::shared_ptr<EventType>& event_type);
+
+    /// Returns current time in emulated CPU cycles
+    u64 GetCPUTicks() const;
+
+    /// Returns current time in emulated in Clock cycles
+    u64 GetClockTicks() const;
+
+    /// Returns current time in microseconds.
+    std::chrono::microseconds GetGlobalTimeUs() const;
+
+    /// Returns current time in nanoseconds.
+    std::chrono::nanoseconds GetGlobalTimeNs() const;
+
+private:
+    struct Event;
+
+    /// Clear all pending events. This should ONLY be done on exit.
+    void ClearPendingEvents();
+
+    static void ThreadEntry(CoreTiming& instance);
+    void Advance();
+
+    sys_time_point start_time;
+
+    u64 global_timer = 0;
+
+    std::chrono::nanoseconds start_point;
+
+    // The queue is a min-heap using std::make_heap/push_heap/pop_heap.
+    // We don't use std::priority_queue because we need to be able to serialize, unserialize and
+    // erase arbitrary events (RemoveEvent()) regardless of the queue order. These aren't
+    // accomodated by the standard adaptor class.
+    std::vector<Event> event_queue;
+    u64 event_fifo_id = 0;
+
+    std::shared_ptr<EventType> ev_lost;
+    bool is_set = false;
+    std::condition_variable condvar;
+    std::mutex inner_mutex;
+    std::unique_ptr<std::thread> timer_thread;
+    std::atomic<bool> shutting_down{};
+};
+
+/// Creates a core timing event with the given name and callback.
+///
+/// @param name     The name of the core timing event to create.
+/// @param callback The callback to execute for the event.
+///
+/// @returns An EventType instance representing the created event.
+///
+std::shared_ptr<EventType> CreateEvent(std::string name, TimedCallback&& callback);
+
+} // namespace Core::Timing