Thread: estimating time remaining

PercentDone is a real number (0.0 -> 1.0) telling how much of the file is complete (0.0 = 0%, 1.0 = 100%).
SecondsTaken contains how many seconds have passed so far.

Code:

long int GetTimeLeft(double PercentDone, long int SecondsTaken)
{
   //Prevent division by 0
   if(PercentDone == 0.0) return 0;

   //Calculate the time remaining
   return (long int)(((double)SecondsTaken / PercentDone) - (double)SecondsTaken + 0.99999);
}

EDIT: The last 0.99999 is for rounding perfection (skip it if you like, who cares for a +/- second )

Is there any function that returns the length of a file?
Example:

Code:

int main(){
   
   ifstream inFile("File.txt");

   cout << "The size of the file is " << inFile.size();

   return 0;
}

This function(if exists) could solve all the problem...

Code:

long int GetFileLength(const char* FileName)
{
   ifstream ReadFile;
   long int Size;

   ReadFile.open(FileName, ios::in | ios::nocreate | ios::binary);
   if(ReadFile.fail())
   {
      return -1;
   }

   ReadFile.seekg(0, ios::end);
   Size = ReadFile.tellg();

   ReadFile.close();
   return Size;
}

Time remaining is never going to be accurate, only an estimate. Consider, you start the copy and nothing else is running, part way through, some heavy resource using program starts or resumes running, now your copy could start running much slower, timings will be out.