Initial Vexta Core v0.1.0 release

src/scheduler.cpp

@@ -0,0 +1,205 @@
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2014-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <scheduler.h>
+
+#include <random.h>
+#include <util/time.h>
+
+#include <assert.h>
+#include <functional>
+#include <utility>
+
+CScheduler::CScheduler()
+{
+}
+
+CScheduler::~CScheduler()
+{
+    assert(nThreadsServicingQueue == 0);
+    if (stopWhenEmpty) assert(taskQueue.empty());
+}
+
+
+void CScheduler::serviceQueue()
+{
+    WAIT_LOCK(newTaskMutex, lock);
+    ++nThreadsServicingQueue;
+
+    // newTaskMutex is locked throughout this loop EXCEPT
+    // when the thread is waiting or when the user's function
+    // is called.
+    while (!shouldStop()) {
+        try {
+            while (!shouldStop() && taskQueue.empty()) {
+                // Wait until there is something to do.
+                newTaskScheduled.wait(lock);
+            }
+
+            // Wait until either there is a new task, or until
+            // the time of the first item on the queue:
+
+            while (!shouldStop() && !taskQueue.empty()) {
+                std::chrono::system_clock::time_point timeToWaitFor = taskQueue.begin()->first;
+                if (newTaskScheduled.wait_until(lock, timeToWaitFor) == std::cv_status::timeout) {
+                    break; // Exit loop after timeout, it means we reached the time of the event
+                }
+            }
+
+            // If there are multiple threads, the queue can empty while we're waiting (another
+            // thread may service the task we were waiting on).
+            if (shouldStop() || taskQueue.empty())
+                continue;
+
+            Function f = taskQueue.begin()->second;
+            taskQueue.erase(taskQueue.begin());
+
+            {
+                // Unlock before calling f, so it can reschedule itself or another task
+                // without deadlocking:
+                REVERSE_LOCK(lock);
+                f();
+            }
+        } catch (...) {
+            --nThreadsServicingQueue;
+            throw;
+        }
+    }
+    --nThreadsServicingQueue;
+    newTaskScheduled.notify_one();
+}
+
+void CScheduler::schedule(CScheduler::Function f, std::chrono::system_clock::time_point t)
+{
+    {
+        LOCK(newTaskMutex);
+        taskQueue.insert(std::make_pair(t, f));
+    }
+    newTaskScheduled.notify_one();
+}
+
+void CScheduler::MockForward(std::chrono::seconds delta_seconds)
+{
+    assert(delta_seconds > 0s && delta_seconds <= 1h);
+
+    {
+        LOCK(newTaskMutex);
+
+        // use temp_queue to maintain updated schedule
+        std::multimap<std::chrono::system_clock::time_point, Function> temp_queue;
+
+        for (const auto& element : taskQueue) {
+            temp_queue.emplace_hint(temp_queue.cend(), element.first - delta_seconds, element.second);
+        }
+
+        // point taskQueue to temp_queue
+        taskQueue = std::move(temp_queue);
+    }
+
+    // notify that the taskQueue needs to be processed
+    newTaskScheduled.notify_one();
+}
+
+static void Repeat(CScheduler& s, CScheduler::Function f, std::chrono::milliseconds delta)
+{
+    f();
+    s.scheduleFromNow([=, &s] { Repeat(s, f, delta); }, delta);
+}
+
+void CScheduler::scheduleEvery(CScheduler::Function f, std::chrono::milliseconds delta)
+{
+    scheduleFromNow([=] { Repeat(*this, f, delta); }, delta);
+}
+
+size_t CScheduler::getQueueInfo(std::chrono::system_clock::time_point& first,
+                                std::chrono::system_clock::time_point& last) const
+{
+    LOCK(newTaskMutex);
+    size_t result = taskQueue.size();
+    if (!taskQueue.empty()) {
+        first = taskQueue.begin()->first;
+        last = taskQueue.rbegin()->first;
+    }
+    return result;
+}
+
+bool CScheduler::AreThreadsServicingQueue() const
+{
+    LOCK(newTaskMutex);
+    return nThreadsServicingQueue;
+}
+
+
+void SingleThreadedSchedulerClient::MaybeScheduleProcessQueue()
+{
+    {
+        LOCK(m_cs_callbacks_pending);
+        // Try to avoid scheduling too many copies here, but if we
+        // accidentally have two ProcessQueue's scheduled at once its
+        // not a big deal.
+        if (m_are_callbacks_running) return;
+        if (m_callbacks_pending.empty()) return;
+    }
+    m_pscheduler->schedule(std::bind(&SingleThreadedSchedulerClient::ProcessQueue, this), std::chrono::system_clock::now());
+}
+
+void SingleThreadedSchedulerClient::ProcessQueue()
+{
+    std::function<void()> callback;
+    {
+        LOCK(m_cs_callbacks_pending);
+        if (m_are_callbacks_running) return;
+        if (m_callbacks_pending.empty()) return;
+        m_are_callbacks_running = true;
+
+        callback = std::move(m_callbacks_pending.front());
+        m_callbacks_pending.pop_front();
+    }
+
+    // RAII the setting of fCallbacksRunning and calling MaybeScheduleProcessQueue
+    // to ensure both happen safely even if callback() throws.
+    struct RAIICallbacksRunning {
+        SingleThreadedSchedulerClient* instance;
+        explicit RAIICallbacksRunning(SingleThreadedSchedulerClient* _instance) : instance(_instance) {}
+        ~RAIICallbacksRunning()
+        {
+            {
+                LOCK(instance->m_cs_callbacks_pending);
+                instance->m_are_callbacks_running = false;
+            }
+            instance->MaybeScheduleProcessQueue();
+        }
+    } raiicallbacksrunning(this);
+
+    callback();
+}
+
+void SingleThreadedSchedulerClient::AddToProcessQueue(std::function<void()> func)
+{
+    assert(m_pscheduler);
+
+    {
+        LOCK(m_cs_callbacks_pending);
+        m_callbacks_pending.emplace_back(std::move(func));
+    }
+    MaybeScheduleProcessQueue();
+}
+
+void SingleThreadedSchedulerClient::EmptyQueue()
+{
+    assert(!m_pscheduler->AreThreadsServicingQueue());
+    bool should_continue = true;
+    while (should_continue) {
+        ProcessQueue();
+        LOCK(m_cs_callbacks_pending);
+        should_continue = !m_callbacks_pending.empty();
+    }
+}
+
+size_t SingleThreadedSchedulerClient::CallbacksPending()
+{
+    LOCK(m_cs_callbacks_pending);
+    return m_callbacks_pending.size();
+}