Get permain and check if it's prewarm

LaunchTracker.swift

/// iOS 15+
func isPrewarm() -> Bool {
    if let prewawrmEnv = ProcessInfo.processInfo.environment["ActivePrewarm"],
       prewawrmEnv == "1" {
        return true
    } else {
        return false
    }
}


/// Call this at main()
/// return: time in milliseconds
func getPreMainDuration() -> Double {
    let currentTimeIntervalInMilliSecond = Date().timeIntervalSince1970 * 1000.0
    var procInfo = kinfo_proc()
    let pid = ProcessInfo.processInfo.processIdentifier
    var cmd: [Int32] = [CTL_KERN, KERN_PROC, KERN_PROC_PID, pid]
    var size = MemoryLayout.stride(ofValue: procInfo)
    // Retrieve information of current process
    if sysctl(&cmd, UInt32(cmd.count), &procInfo, &size, nil, 0) == 0 {
        // tv_sec -> timestamp in second; tv_usec -> rest fraction part in microsecond
        let tvSecInMilliseconds = Double(procInfo.kp_proc.p_un.__p_starttime.tv_sec) * 1000.0
        let tvUsecInMilliseconds = Double(procInfo.kp_proc.p_un.__p_starttime.tv_usec) / 1000.0
        let processCreationTime = tvSecInMilliseconds + tvUsecInMilliseconds
        var premainTime = currentTimeIntervalInMilliSecond - processCreationTime
        premainTime.round()
        return premainTime
    } else {
        print("Can't retrieve information of exeuction process")
        return 0
    }
}