millis64()

fl::u64 fl::millis64

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64-bit millisecond timer - returns milliseconds since system startup without wraparound

This function provides a 64-bit millisecond counter that never wraps around in any practical timeframe (584 million years). It's built on top of fl::millis() and automatically detects and corrects for 32-bit wraparound.

The implementation uses a function-local static for thread-safe accumulation on platforms that support it. On platforms with native 64-bit timers, this function may be optimized to use the native implementation directly.

Returns

Number of milliseconds since system startup as a 64-bit value

Note

Thread-safe on platforms with proper static initialization guards

No wraparound in practical usage (584+ million years)

Slightly higher overhead than millis() due to wraparound detection

Examples

// Long-running timing without wraparound concerns
fl::u64 start = fl::millis64();
long_running_operation();
fl::u64 elapsed = fl::millis64() - start;
 
// Safe duration tracking across 49+ day boundaries
static fl::u64 session_start = fl::millis64();
fl::u64 uptime = fl::millis64() - session_start; // Never wraps
 
// Timestamps for logging and analytics
fl::u64 event_time = fl::millis64();
log_event("operation_complete", event_time);

Definition at line 173 of file chrono.cpp.hpp.

                              {
    Millis64State& state = get_millis64_state();
    fl::u32 current_millis = fl::millis();
    fl::unique_lock<fl::mutex> lock(state.mutex);
 
    if (!state.initialized) {
        // First call, set initial value
        state.accumulated = current_millis;
        state.last_millis = current_millis;
        state.initialized = true;
        return state.accumulated;
    }
 
    // Detect wraparound: current < last means 32-bit counter wrapped
    // Delta calculation handles wraparound correctly via unsigned arithmetic
    fl::u32 delta = current_millis - state.last_millis;
 
    // Accumulate the delta into 64-bit counter
    state.accumulated += delta;
 
    // Update last value for next call
    state.last_millis = current_millis;
 
    return state.accumulated;
}

References FL_NO_EXCEPT, millis(), and state.

Referenced by time().

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