From ecacf7f9f750db0cc33dc05753c1ad9210d878e4 Mon Sep 17 00:00:00 2001
From: niansa <anton-sa@web.de>
Date: Mon, 22 May 2023 22:46:30 +0200
Subject: [PATCH] Implemented experimental async mutex

---
 CMakeLists.txt              |  1 +
 include/scheduler_mutex.hpp | 67 +++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 include/scheduler_mutex.hpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 92d0772..e19f192 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,6 +8,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 add_library(cosched SHARED
     scheduler.cpp include/scheduler.hpp
     scheduled_thread.cpp include/scheduled_thread.hpp
+    include/scheduler_mutex.hpp
     basic-coro/SingleEvent.cpp
 )
 target_include_directories(cosched PUBLIC include/ basic-coro/include/)
diff --git a/include/scheduler_mutex.hpp b/include/scheduler_mutex.hpp
new file mode 100644
index 0000000..ed995f5
--- /dev/null
+++ b/include/scheduler_mutex.hpp
@@ -0,0 +1,67 @@
+#ifndef SCHEDULER_MUTEX_HPP
+#define SCHEDULER_MUTEX_HPP
+#include "scheduler.hpp"
+
+#include <queue>
+
+
+namespace CoSched {
+class Mutex {
+    bool held = false;
+    std::queue<Task*> resume_on_unlock;
+
+public:
+    Mutex() {}
+    Mutex(const Mutex&) = delete;
+    Mutex(Mutex&&) = delete;
+    ~Mutex() {
+        unlock();
+    }
+
+    AwaitableTask<void> lock() {
+        // Just hold lock and return if lock isn't currently being held
+        if (!held) {
+            held = true;
+            co_return;
+        }
+        // Lock is already being held, add task to queue and suspend until lock is passed
+        auto& task = Task::get_current();
+        resume_on_unlock.push(&task);
+        task.set_suspended(true);
+        co_await task.yield();
+    }
+    void unlock() {
+        // If nothing is waiting for the lock to release, just release it and we're done
+        if (!resume_on_unlock.empty()) {
+            held = false;
+            return;
+        }
+        // Something is waiting or the lock to be released, just pass it by.
+        resume_on_unlock.front()->set_suspended(false);
+    }
+};
+
+
+class ScopedLock {
+    Mutex& mutex;
+    bool held_by_us = false;
+
+public:
+    ScopedLock(Mutex &m) : mutex(m) {}
+    ScopedLock(const ScopedLock&) = delete;
+    ScopedLock(ScopedLock&&) = delete;
+    ~ScopedLock() {
+        if (held_by_us) unlock();
+    }
+
+    AwaitableTask<void> lock() {
+        co_await mutex.lock();
+        held_by_us = true;
+    }
+    void unlock() {
+        mutex.unlock();
+        held_by_us = false;
+    }
+};
+}
+#endif // SCHEDULER_MUTEX_HPP