Add operator support to collision guard

Fixed a bug that caused a race between ~Thread and Thread::Runner receiving a new job from the threadpool

CMakeLists.txt

@@ -9,7 +9,15 @@ file(GLOB_RECURSE HEADERS "include/*.h" "include/*.hpp")
 file(GLOB_RECURSE SOURCES "src/*.c" "src/*.cpp")
 set(CMAKE_CXX_STANDARD 20)
 
-add_library(MultiThreading SHARED ${SOURCES})
+if (UNIX AND NOT APPLE)
+    add_library(MultiThreading SHARED ${SOURCES} "include/MultiThreading/CollisionGuard.h")
+endif()
+
+if(WIN32)
+    add_library(MultiThreading STATIC ${SOURCES} "include/MultiThreading/CollisionGuard.h")
+endif()
+
 target_include_directories(MultiThreading PUBLIC ${PROJECT_SOURCE_DIR}/include)
+
 add_executable(MultiThreadingDemo main.cpp)
 target_link_libraries(MultiThreadingDemo PUBLIC MultiThreading)

README.md

@@ -0,0 +1,46 @@
+# Redacted Software MultiThreading 
+
+Yet Another C++ Threading Library
+
+[![License: Unlicense](https://img.shields.io/badge/license-Unlicense-blue.svg)](http://unlicense.org/) ![Static Badge](https://img.shields.io/badge/Lit-Based-%20)
+
+## Features
+
+* Easily utilize maximum parallelization of the hardware.
+* Overhead < 1% compared to running functions directly.
+* Thread-safe wrappers for common STL data structures.
+* Public Domain Source Code.
+
+## API Overview
+
+## Types
+* CollisionGuard
+* ConcurrentQueue
+* Task
+* Thread
+* ThreadPool
+
+## Usage
+
+Using a thread-pool to execute a large set of tasks, which will utilize as many hardware threads as possible.
+
+## Requirements
+
+* C++ 20
+
+## Compatibility
+
+* Linux (gcc 13.x or newer)
+* Windows 10 (1909 or newer)
+
+## Documentation
+
+Documentation is currently limited to source-code annotations, and the demo program.
+
+## Contributing
+
+Contributions to MultiThreading are welcome! If you find a bug, have a feature request, or would like to contribute code, please submit an issue or pull request.
+
+## Acknowledgements
+
+Developed & Maintained by William @ Redacted Software and contributors. 

include/MultiThreading/CollisionGuard.h

@@ -0,0 +1,113 @@
+#pragma once
+
+#include <concepts>
+#include <shared_mutex>
+
+namespace MultiThreading {
+    template <typename T>
+    class CollisionGuard;
+}
+template <typename T>
+class MultiThreading::CollisionGuard {
+private:
+    mutable std::shared_mutex mutex;
+    T value;
+public:
+
+    class Read {
+    private:
+        std::shared_lock<std::shared_mutex> lock;
+        const T* t_ptr;
+    public:
+        Read(const std::shared_mutex& mtx, const T& val) : t_ptr(&val), lock(mtx) {}
+        const T* operator->() const { return t_ptr; }
+    };
+
+    class Write {
+    private:
+        std::unique_lock<std::shared_mutex> lock;
+        T* t_ptr;
+    public:
+        Write(std::shared_mutex& mtx, T& val) : t_ptr(&val), lock(mtx) {}
+        T* operator->() { return t_ptr; }
+    };
+public:
+    Read operator->() const { return Read(mutex, value); }
+    Write operator->() { return Write(mutex, value); }
+public:
+    template <typename U = T>
+    requires requires(const U& a, const U& b) { a + b; }
+    T operator +(const T& rhs) const {
+        std::shared_lock lock(mutex);
+        return value + rhs;
+    }
+
+    template <typename U = T>
+    requires requires(U& a, const U& b) { a = b; }
+    CollisionGuard& operator =(const T& rhs) {
+        std::unique_lock lock(mutex);
+        value = rhs;
+        return *this;
+    }
+
+    explicit operator T() const requires std::copy_constructible<T> {
+        std::shared_lock lock(mutex);
+        return value;
+    }
+
+    template <typename U = T>
+    requires requires(U& a, const U& b) { a += b; }
+    CollisionGuard& operator +=(const T& rhs) {
+        std::unique_lock lock(mutex);
+        value += rhs;
+        return *this;
+    }
+
+    template <typename U = T>
+    requires requires(U& a, const U& b) { a -= b; }
+    CollisionGuard& operator -=(const T& rhs) {
+        std::unique_lock lock(mutex);
+        value -= rhs;
+        return *this;
+    }
+
+    template <typename U = T>
+    requires requires(U& a, const U& b) { a *= b; }
+    CollisionGuard& operator *=(const T& rhs) {
+        std::unique_lock lock(mutex);
+        value *= rhs;
+        return *this;
+    }
+
+    template <typename U = T>
+    requires requires(U& a, const U& b) { a /= b; }
+    CollisionGuard& operator /=(const T& rhs) {
+        std::unique_lock lock(mutex);
+        value /= rhs;
+        return *this;
+    }
+
+    template <typename U = T>
+    requires requires(const U& a, const U& b) { a - b; }
+    T operator -(const T& rhs) const {
+        std::shared_lock lock(mutex);
+        return value - rhs;
+    }
+
+    template <typename U = T>
+    requires requires(const U& a, const U& b) { a * b; }
+    T operator *(const T& rhs) const {
+        std::shared_lock lock(mutex);
+        return value * rhs;
+    }
+
+    template <typename U = T>
+    requires requires(const U& a, const U& b) { a / b; }
+    T operator /(const T& rhs) const {
+        std::shared_lock lock(mutex);
+        return value / rhs;
+    }
+public:
+    template <typename... Args>
+    explicit CollisionGuard(Args&&... args) : value(std::forward<Args>(args)...) {}
+};

include/MultiThreading/Task.h

@@ -20,6 +20,8 @@ protected:
     std::atomic<bool> complete = false;
     std::mutex mtx;
     void MarkTaskComplete() { std::lock_guard<std::mutex> lock(mtx); complete = true; completed_condition.notify_all(); }
+protected:
+    explicit TaskBase(std::function<void()> task_complete_callback = nullptr) : complete_callback(std::move(task_complete_callback)) {};
 public:
     /// @returns whether the task is finished.
     [[nodiscard]] bool Complete() const { return complete; }
@@ -29,8 +31,6 @@ public:
     void WaitComplete() { std::unique_lock<std::mutex> lock(mtx); completed_condition.wait(lock, [this]() { return complete.load(); }); }
 
     virtual void Run() = 0;
-public:
-    explicit TaskBase(std::function<void()> task_complete_callback = nullptr) : complete_callback(std::move(task_complete_callback)) {};
 };
 
 template <typename T>
@@ -45,8 +45,10 @@ public:
 public:
     /// Create a Task. This is non-negotiable, This ensures that there's no issues related to the stack frame the task is on being popped before or while the job runs.
     /// @param callable The function to run, *usually a lambda or std::bind*
+    /// @param complete_callback A void callable to be run after the task.
     /// @param result If your function returns a value, This is where you want it to go. nullptr for no return value or you don't want it.
-    /// @note this is shared_ptr so you don't have to delete it.
+    /// @note If result is stack allocated your program will probably explode.
+    /// @note this is shared_ptr so that you don't have to delete it.
     static std::shared_ptr<Task<T>> Create(std::function<T()> callable, const std::function<void()>& complete_callback = nullptr, T* result = nullptr) { return std::shared_ptr<Task<T>>(new Task<T>(callable, complete_callback, result)); };
     ~Task() = default;
 };
@@ -62,7 +64,8 @@ public:
 
     /// Create a Task. This is non-negotiable, This ensures that there's no issues related to the stack frame the task is on being popped before or while the job runs.
     /// @param callable The function to run, *usually a lambda or std::bind*
-    /// @note this is shared_ptr so you don't have to delete it.
+    /// @param complete_callback A void callable to be run after the task.
+    /// @note this is shared_ptr so that you don't have to delete it.
     static std::shared_ptr<Task<void>> Create(const std::function<void()>& callable, const std::function<void()>& complete_callback = nullptr) { return std::shared_ptr<Task<void>>(new Task<void>(callable, complete_callback)); }
     ~Task() = default;
 };

include/MultiThreading/ThreadPool.h

@@ -15,6 +15,7 @@ private:
     std::queue<std::shared_ptr<TaskBase>> queue;
     std::condition_variable queue_condition;
     std::mutex queue_mutex;
+    bool destructing = false;
 private:
     /// @returns nullptr if the queue is empty.
     std::shared_ptr<TaskBase> Dequeue();
@@ -22,11 +23,11 @@ private:
 public:
     /// Set a task to be run on the thread-pool.
     /// @param task The task to run.
-    void Enqueue(const std::shared_ptr<MultiThreading::TaskBase>& task);
+    bool Enqueue(const std::shared_ptr<MultiThreading::TaskBase>& task);
 
     /// Set a task to be run on the thread-pool.
     /// @param task The task to run.
-    void Enqueue(const std::function<void()>& task);
+    bool Enqueue(const std::function<void()>& task);
 public:
     /// @returns The number of threads in the thread pool.
     [[nodiscard]] unsigned int ThreadCount() const { return threads.size(); }
@@ -35,7 +36,7 @@ public:
     /// @note this excludes the tasks currently being run.
     [[nodiscard]] unsigned int PendingTasks();
 
-    /// @returns Whether a task you enqueue would have to wait for something else to finish.
+    /// @returns Whether a task you enqueue would have to wait for something else to finish before running.
     [[nodiscard]] bool Busy();
 
     /// Uses a condition variable to wait the calling thread until the queue is empty.
@@ -48,6 +49,5 @@ public:
 
     /// Waits for the threads to empty the queue and destroys the thread pool.
     /// @note This should be one of the very last things your program does before exiting.
-    // TODO make Enqueue fail during destruction to avoid stalls.
     ~ThreadPool();
 };

main.cpp

@@ -1,16 +1,15 @@
 #include <MultiThreading/Task.h>
-#include <MultiThreading/Thread.h>
 #include <MultiThreading/ThreadPool.h>
+#include <MultiThreading/CollisionGuard.h>
 
 #include <iostream>
 
 using namespace MultiThreading;
 
-void cb() { std::cout << "hi" << std::endl; }
-int32_t some_test_func(int32_t hello) {
+//void cb() { std::cout << "hi" << std::endl; }
+void some_test_func() {
     for (unsigned int i = 0; i < 1000000000; i++) {}
-    std::cout << "task " << hello << " finishes." << std::endl;
-    return rand();
+    std::cout << "task finishes." << std::endl;
 }
 
 /*
@@ -42,21 +41,16 @@ int main() {
 }
 */
 
-
-
 int main() {
     srand(time(nullptr));
-
-    int32_t task_completion_count = 0;
-    auto* thread_pool = new ThreadPool(16);
-
+    CollisionGuard<int> task_completion_count(0);
+    auto* thread_pool = new ThreadPool();
 
     for (unsigned int i = 0; i < 128; i++) {
-        auto some_task = Task<int32_t>::Create(([i] { return some_test_func(i); }), cb, &task_completion_count);
+        auto some_task = Task<void>::Create([&task_completion_count]() { task_completion_count += 1; }, [&task_completion_count]() { task_completion_count += 1; });
         thread_pool->Enqueue(some_task);
     }
 
-    /// do stuff after the job.
     delete thread_pool;
-    std::cout << "The returned random value was: " << task_completion_count << std::endl;
+    std::cout << "The number of tasks run was " << (int) task_completion_count << std::endl;
 }

src/Thread.cpp

@@ -1,16 +1,23 @@
-#include <MultiThreading/Thread.h>
 #include <utility>
+#include <MultiThreading/Thread.h>
+
 
 using namespace MultiThreading;
 
 Thread::~Thread() {
-    if (current_task)
-        current_task->WaitComplete();
-    stop = true;
+    std::shared_ptr<TaskBase> task;
 
+    {
+        std::lock_guard<std::mutex> lock(mtx);
+        task = current_task;
+    }
+
+    if (task)
+        task->WaitComplete();
+
+    stop = true;
     cv.notify_one();
     Join();
-    // Thread exits gracefully.
 }
 
 bool Thread::SetTask(std::shared_ptr<TaskBase> task) {
@@ -42,9 +49,10 @@ void Thread::Runner() {
         if (stop)
             break;
 
+        auto task = current_task;
         lock.unlock();
 
-        current_task->Run();
+        task->Run();
 
         lock.lock();
 

src/ThreadPool.cpp

@@ -8,7 +8,10 @@ ThreadPool::ThreadPool(unsigned int thread_count) {
         threads.push_back(new Thread());
 }
 
-void ThreadPool::Enqueue(const std::shared_ptr<MultiThreading::TaskBase>& task) {
+bool ThreadPool::Enqueue(const std::shared_ptr<MultiThreading::TaskBase>& task) {
+    if (destructing)
+        return false;
+
     std::lock_guard<std::mutex> lock(queue_mutex);
 
     // Assign it immediately if there's no wait and a thread open.
@@ -19,12 +22,13 @@ void ThreadPool::Enqueue(const std::shared_ptr<MultiThreading::TaskBase>& task)
 
             if (!t->SetTask( [this, task] (){ Runner(task); } ))
                 throw std::runtime_error("There was a collision while putting the task to the thread.");
-            return;
+            return true;
         }
     }
 
     // Alternatively it goes in-to the queue.
     queue.push(task);
+    return true;
 }
 
 std::shared_ptr<TaskBase> ThreadPool::Dequeue() {
@@ -41,8 +45,8 @@ std::shared_ptr<TaskBase> ThreadPool::Dequeue() {
     return task;
 }
 
-void ThreadPool::Enqueue(const std::function<void()>& task) {
-    Enqueue(Task<void>::Create(task));
+bool ThreadPool::Enqueue(const std::function<void()>& task) {
+    return Enqueue(Task<void>::Create(task));
 }
 
 void ThreadPool::Runner(const std::shared_ptr<TaskBase>& task) {
@@ -62,6 +66,7 @@ unsigned int ThreadPool::PendingTasks() {
 }
 
 ThreadPool::~ThreadPool() {
+    destructing = true;
     // Wait for all queued tasks to be running.
     WaitQueueEmpty();