From 2aa4600c57edb7a887e336c9061a8fed06cbaf9c Mon Sep 17 00:00:00 2001
From: Stephen Seo <seo.disparate@gmail.com>
Date: Thu, 6 Jun 2019 16:40:04 +0900
Subject: [PATCH] Create Thread-Safe-Queue (untested)

---
 cpp_impl/.gitignore      |  1 +
 cpp_impl/CMakeLists.txt  |  1 +
 cpp_impl/src/TSQueue.cpp | 72 ++++++++++++++++++++++++++++++++++++++++
 cpp_impl/src/TSQueue.hpp | 37 +++++++++++++++++++++
 4 files changed, 111 insertions(+)
 create mode 100644 cpp_impl/src/TSQueue.cpp
 create mode 100644 cpp_impl/src/TSQueue.hpp

diff --git a/cpp_impl/.gitignore b/cpp_impl/.gitignore
index 5c322f8..97008fa 100644
--- a/cpp_impl/.gitignore
+++ b/cpp_impl/.gitignore
@@ -1,3 +1,4 @@
 build*/
+.clangd/
 compile_commands.json
 *.o
diff --git a/cpp_impl/CMakeLists.txt b/cpp_impl/CMakeLists.txt
index f8b89d9..196674a 100644
--- a/cpp_impl/CMakeLists.txt
+++ b/cpp_impl/CMakeLists.txt
@@ -5,6 +5,7 @@ set(UDPConnection_VERSION 1.0)
 
 set(UDPConnection_SOURCES
     src/UDPConnection.cpp
+    src/TSQueue.cpp
 )
 
 set(CMAKE_CXX_FLAGS "-Wall -Wextra -Wpedantic -Wno-missing-braces")
diff --git a/cpp_impl/src/TSQueue.cpp b/cpp_impl/src/TSQueue.cpp
new file mode 100644
index 0000000..a5e836b
--- /dev/null
+++ b/cpp_impl/src/TSQueue.cpp
@@ -0,0 +1,72 @@
+#include "TSQueue.hpp"
+
+#include <cstring>
+
+TSQueue::TSQueue(unsigned int elemSize, unsigned int capacity)
+    : elemSize(elemSize), capacity(capacity), head(0), tail(0), isEmpty(true),
+      spinLock(false) {
+    if (elemSize == 0) {
+        this->elemSize = 1;
+    }
+    if (capacity == 0) {
+        this->capacity = UDPC_TSQUEUE_DEFAULT_CAPACITY * this->elemSize;
+    }
+
+    this->buffer =
+        std::unique_ptr<unsigned char[]>(new unsigned char[this->capacity]);
+}
+
+TSQueue::~TSQueue() {}
+
+bool TSQueue::push(void *data) {
+    while (spinLock.exchange(true) == true) {
+    }
+    if (!isEmpty && head == tail) {
+        spinLock.store(false);
+        return false;
+    }
+
+    memcpy(buffer.get() + tail, data, elemSize);
+    tail = (tail + elemSize) % capacity;
+
+    isEmpty = false;
+
+    spinLock.store(false);
+    return true;
+}
+
+std::unique_ptr<unsigned char[]> TSQueue::top() {
+    while (spinLock.exchange(true) == true) {
+    }
+    if (isEmpty) {
+        spinLock.store(false);
+        return std::unique_ptr<unsigned char[]>();
+    }
+
+    auto data = std::unique_ptr<unsigned char[]>(new unsigned char[elemSize]);
+    if (tail != 0) {
+        memcpy(data.get(), buffer.get() + (tail - elemSize), elemSize);
+    } else {
+        memcpy(data.get(), buffer.get() + (capacity - elemSize), elemSize);
+    }
+    spinLock.store(false);
+    return data;
+}
+
+bool TSQueue::pop() {
+    while (spinLock.exchange(true) == true) {
+    }
+    if (isEmpty) {
+        spinLock.store(false);
+        return false;
+    }
+    head += elemSize;
+    if (head >= capacity) {
+        head = 0;
+    }
+    if (head == tail) {
+        isEmpty = true;
+    }
+    spinLock.store(false);
+    return true;
+}
diff --git a/cpp_impl/src/TSQueue.hpp b/cpp_impl/src/TSQueue.hpp
new file mode 100644
index 0000000..b1626c4
--- /dev/null
+++ b/cpp_impl/src/TSQueue.hpp
@@ -0,0 +1,37 @@
+#ifndef UDPC_THREADSAFE_QUEUE_HPP
+#define UDPC_THREADSAFE_QUEUE_HPP
+
+#define UDPC_TSQUEUE_DEFAULT_CAPACITY 32
+
+#include <atomic>
+#include <cstdlib>
+#include <memory>
+
+class TSQueue {
+  public:
+    TSQueue(unsigned int elemSize,
+            unsigned int capacity = UDPC_TSQUEUE_DEFAULT_CAPACITY);
+    ~TSQueue();
+
+    // disable copy
+    TSQueue(const TSQueue &other) = delete;
+    TSQueue &operator=(const TSQueue &other) = delete;
+    // disable move
+    TSQueue(TSQueue &&other) = delete;
+    TSQueue &operator=(TSQueue &&other) = delete;
+
+    bool push(void *data);
+    std::unique_ptr<unsigned char[]> top();
+    bool pop();
+
+  private:
+    unsigned int elemSize;
+    unsigned int capacity;
+    unsigned int head;
+    unsigned int tail;
+    bool isEmpty;
+    std::unique_ptr<unsigned char[]> buffer;
+    std::atomic_bool spinLock;
+};
+
+#endif