Asynchronous Mutex Implementation in Rust

This challenge asks you to implement an asynchronous mutex in Rust using async-std. Asynchronous mutexes are crucial for safely sharing mutable data between multiple asynchronous tasks, preventing race conditions and ensuring data integrity in concurrent environments. This is a fundamental building block for many asynchronous applications.

Problem Description

You are tasked with creating an AsyncMutex struct that provides mutual exclusion capabilities within an asynchronous context. The AsyncMutex should allow multiple asynchronous tasks to safely access and modify shared data. It should provide lock() and try_lock() methods that operate asynchronously, blocking the calling task until the mutex is available.

Key Requirements:

• lock() method: This method should asynchronously acquire the mutex. If the mutex is already locked, the calling task should be suspended until the mutex becomes available. It should return a MutexGuard that provides exclusive access to the protected data.
• try_lock() method: This method should attempt to acquire the mutex asynchronously. If the mutex is already locked, it should immediately return None. If the mutex is available, it should acquire the lock and return a MutexGuard.
• MutexGuard struct: This struct should provide exclusive access to the protected data while the mutex is held. It should automatically release the mutex when it goes out of scope (using Drop).
• Asynchronous Operation: All locking and unlocking operations must be performed asynchronously using async-std.

Expected Behavior:

• Multiple tasks should be able to attempt to acquire the mutex concurrently.
• Only one task should be able to hold the mutex at any given time.
• Tasks waiting for the mutex should be woken up when the mutex becomes available.
• The MutexGuard should ensure exclusive access to the protected data while held.
• The mutex should be automatically released when the MutexGuard goes out of scope.

Edge Cases to Consider:

• What happens if a task tries to lock a mutex it already holds? (Should panic or allow it?) For this challenge, allow it.
• How to handle potential errors or panics within the critical section protected by the mutex? (This challenge doesn't require explicit error handling, but consider it for robustness.)
• Consider the performance implications of the locking mechanism.

Examples

Example 1:

Input: Two asynchronous tasks attempting to lock the mutex sequentially.
Output: Task 1 acquires the mutex, Task 2 waits until Task 1 releases it, then Task 2 acquires it.
Explanation: Demonstrates basic mutex acquisition and release.

Example 2:

Input: Multiple asynchronous tasks attempting to lock the mutex concurrently.
Output: Tasks are queued in FIFO order, and acquire the mutex one at a time.
Explanation: Shows concurrent locking behavior.

Example 3:

Input: A task attempts to `try_lock()` a mutex that is already locked.
Output: `None` is returned immediately.
Explanation: Demonstrates the non-blocking behavior of `try_lock()`.

Constraints

• The implementation must use async-std for asynchronous operations.
• The AsyncMutex should be thread-safe.
• The MutexGuard should provide exclusive access to the protected data.
• The code should be reasonably efficient. While micro-optimizations aren't required, avoid unnecessary overhead.
• The code should be well-documented and easy to understand.

Notes

• You can use async-std::sync::Mutex as a reference for how to structure your code, but you are not allowed to directly use it. The goal is to implement the core logic yourself.
• Consider using an AtomicBool or similar mechanism to track the mutex's locked state.
• Think about how to efficiently queue waiting tasks. async-std::task provides tools for managing tasks.
• The Drop trait on MutexGuard is crucial for automatic mutex release. Ensure it's implemented correctly.
• Focus on correctness and clarity first, then consider performance optimizations if time allows.