C to C++

# Converting a Multithreaded Proxy Server from C to C++ with Minimal Changes

There is not much to do if you want to change this codebase into c++. Here are some recommendations.

---

## 1. File Extensions

- Rename `.c` files to `.cpp`.
- Optionally, rename `.h` files to `.hpp`.

---

## 2. Include Statements

- Replace C headers with C++ counterparts:
  ```cpp
  #include <cstdio>
  #include <cstdlib>
  #include <cstring>
  #include <cerrno>
  ```
- Add necessary C++ headers:
  ```cpp
  #include <iostream>
  #include <string>
  ```

---

## 3. Namespace Usage

- Add `using namespace std;` or prefix standard library elements with `std::`.

---

## 4. String Handling

- Optionally replace `char*` with `std::string` for safer memory management:
  ```cpp
  char buffer[BUFFER_SIZE];
  strcpy(buffer, "Hello");

  // Optional C++ update
  std::string buffer = "Hello";
  ```

---

## 5. Dynamic Memory Allocation

- In C++, you can still use `malloc` and `free`, as C++ maintains backward compatibility with C. However, using `new` and `delete` is recommended:
  ```cpp
  char* str = (char*)malloc(size);
  free(str);

  // Optional C++ update
  char* str = new char[size];
  delete[] str;
  ```

---

## 6. Multithreading

- POSIX threads still work in C++:
  ```cpp
  pthread_t thread_id;
  pthread_create(&thread_id, nullptr, handle_client, (void*)&client_sock);
  pthread_detach(thread_id);
  ```
- Optional C++ update:
  ```cpp
  std::thread t(handle_client, client_sock);
  t.detach();
  ```

---

## 7. Synchronization

- `pthread_mutex_t` works as usual:
  ```cpp
  pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
  pthread_mutex_lock(&mutex);
  pthread_mutex_unlock(&mutex);
  ```
- Optional C++ update:
  ```cpp
  std::mutex mutex;
  mutex.lock();
  mutex.unlock();
  ```

---

## 8. Error Handling

- Traditional error handling with `fprintf` remains valid:
  ```cpp
  if (error) {
      fprintf(stderr, "Error: %s\n", strerror(errno));
      exit(1);
  }
  ```
- Optional C++ exception handling:
  ```cpp
  if (error) {
      std::cerr << "Error: " << strerror(errno) << std::endl;
      throw std::runtime_error("Operation failed");
  }
  ```

---

## 9. I/O Operations

- `printf` and `fprintf` work as usual:
  ```cpp
  printf("Connected to %s\n", address);
  ```
- Optional C++ update:
  ```cpp
  std::cout << "Connected to " << address << std::endl;
  ```

---

## 10. Constants

- `#define` works in C++ but `const` or `constexpr` is safer:
  ```cpp
  #define BUFFER_SIZE 1024

  // Optional C++ update
  const int BUFFER_SIZE = 1024;
  ```

---

## 11. Function Prototypes

- No change required, but inline functions are possible:
  ```cpp
  inline void some_function() {
      // Implementation
  }
  ```

---

## 12. Type Casting

- C-style casts work in C++, but C++ casts are safer:
  ```cpp
  int* p = (int*)malloc(sizeof(int));

  // Optional C++ update
  int* p = static_cast<int*>(malloc(sizeof(int)));
  ```

---

## 13. Structures

- `struct` works the same in C++:
  ```cpp
  struct Cache {
      // members
  };
  ```
- Optional C++ class for encapsulation:
  ```cpp
  class Cache {
  public:
      // public members
  private:
      // private members
  };
  ```

---

## 14. Main Function

- The `main` signature remains valid:
  ```cpp
  int main(void) {
      // ...
  }
  ```
- Optional C++ update:
  ```cpp
  int main() {
      // ...
  }
  ```

---

By following these steps, you can convert a C-based multithreaded proxy server to C++ with minimal effort while taking advantage of modern C++ features.