RAII and Resource Management

Resource Acquisition Is Initialization

RAII is C++'s most important pattern: tie resource lifetimes to object lifetimes so cleanup happens automatically — even if exceptions are thrown:

class MutexGuard {
    mutex& mtx;
public:
    MutexGuard(mutex& m) : mtx(m) { mtx.lock(); }
    ~MutexGuard()                  { mtx.unlock(); }

    // Non-copyable — unique ownership
    MutexGuard(const MutexGuard&) = delete;
    MutexGuard& operator=(const MutexGuard&) = delete;
};

mutex m;
void criticalSection() {
    MutexGuard guard(m);   // locks
    // ... do work ...
}   // guard's destructor unlocks, no matter what

RAII in the standard library

• unique_ptr / shared_ptr — memory
• lock_guard / unique_lock — mutex locks
• ifstream / ofstream — file handles

Your Task

Implement a Timer RAII class that records the start time in its constructor and provides getElapsedMs() returning elapsed milliseconds as long long.