elaspsed() - Time elapsed down to milliseconds

string elapsed(string sTime)
----------------------------
Chromal Brodsky - 2005-01-05

elapsed() uses the highest precision clock available in LSL, llGetTimestamp(), to implement a timer with greater than one-second precision.

Typical use:

string sStart = elapsed("";
some_function();
string sElapsed = elapsed(sStart);

At the end of the above example, sElapsed is in the format of hh:mms.ssssss, e.g.: "00:01:10.605000"

// string elapsed(string sTime)
// ----------------------------
// Chromal Brodsky - 2005-01-05
//
// elapsed() uses the highest precision clock available in LSL, llGetTimestamp(),
// to implement a timer with greater than one-second precision.
//
// Typical use:
//
//      string sStart = elapsed("");
//      some_function();
//      string sElapsed = elapsed(sStart);
//
// At the end of the above example, sElapsed is in the format of hh:mm:ss.ssssss,
// e.g.: "00:01:10.605000"
//
// On Lusk running at 1000 FPS on sim367.agni.lindenlab.com,
// I sampled the following times for { sTime = elapsed(""); llWhisper(0, elapsed(sTime) );}
//
//      00:00:00.010000     00:00:00.003000     00:00:00.003000     00:00:00.003998
//      00:00:00.002998     00:00:00.003002     00:00:00.012000     00:00:00.004001
//      00:00:00.004000     00:00:00.005001     00:00:00.003000     00:00:00.004999
// YMMV

string elapsed(string sTime)
{
    if (sTime == "" )
    {
        sTime = llGetTimestamp();                          
    }
    else
    {
        string sH;
        string sM;
        string sS;
        
        string sTimeEnd = llGetTimestamp();
        
        integer iHour = (integer)llGetSubString( sTimeEnd, 11, 12 );
        integer iMin =  (integer)llGetSubString( sTimeEnd, 14, 15 );
        float fSec =      (float)llGetSubString( sTimeEnd, 17, 22 );
        
        integer iHour_start =   (integer)llGetSubString( sTime, 11, 12 );
        integer iMin_start =    (integer)llGetSubString( sTime, 14, 15 );
        float fSec_start =        (float)llGetSubString( sTime, 17, 22 );
        
        if (iHour < iHour_start) 
        {
            iHour += 24;
        }
        if (iMin < iMin_start)
        {
            iMin += 60;
        }
        if (fSec < fSec_start)
        {
            fSec += 60.0;
        }

        iHour = iHour - iHour_start;
        iMin = iMin - iMin_start;
        fSec = fSec - fSec_start;

        if (iHour < 10)
        {
            sH = "0";
        }
        if (iMin < 10)
        {
            sM = "0";
        }
        if (fSec < 10.0)
        {
            sS = "0";
        }
                                                    
        sTime = sM + (string)iHour + ":" + sM + (string)iMin + ":" + sS + (string)fSec;        
    }
    
    return sTime;
}