Thread-Safe File Writing

To ensure thread-safe file writing in a multi-threaded application, you must control access to the file so that only one thread can write at a time. This can be achieved using mutexes (mutual exclusions), which prevent multiple threads from writing to the file simultaneously.

Here’s an example using C++’s standard library std::mutex:

1#include <SDL.h>
2#include <iostream>
3#include <mutex>
4#include <cstring>
5
6std::mutex FileMutex; 
7
8namespace File {
9void Write(const std::string& Path,
10           const char* Content) {
11  std::lock_guard<std::mutex> Lock(
12    FileMutex 
13  );
14
15  SDL_RWops* Handle{
16    SDL_RWFromFile(Path.c_str(), "ab")
17  };
18
19  if (!Handle) {
20    std::cout << "Error opening file: "
21      << SDL_GetError();
22    return;
23  }
24
25  size_t Length{strlen(Content)};
26  SDL_RWwrite(Handle, Content,
27    sizeof(char), Length); 
28
29  SDL_RWclose(Handle);
30}
31}

In this code:

1. We define a std::mutex named FileMutex that will be shared among the threads.
2. The std::lock_guard automatically locks the mutex when a thread enters the Write() function and unlocks it when the thread leaves. This ensures that only one thread can execute the critical section (file writing) at a time.

Why Mutexes Matter

In a multi-threaded environment, if multiple threads try to write to the same file at the same time, the file could become corrupted or the data could be incomplete. Mutexes ensure that these write operations are serialized, meaning they occur one after another in a safe manner.

Alternative Approaches

While mutexes are a simple and effective solution, other approaches like using thread-safe queues or asynchronous I/O can also be used, depending on the complexity and performance requirements of your application.