estimating time remaining

I am working on a c++ program, It basically copys file into another file. I current have the program outputting how many mb it has done and the pecentage of the operation (i.e 5mb out of 50mb 10% complete)

i would also like to add an estimated remaining time and elapsed time if possible. Therefore the output would like like:-

5MB out of 50MB 10% Complete Estimated time remaining 2:21 mins. Total time elapsed 1 min

Any thoughts off how i can do this, please let me know

The sneaky way: just use a random number generator to make up a time.

set a timer for 10 seconds.
after 10 seconds take the percent done. lets say its 10%

you have 9 * 10 seconds left.
divide by 60 to get minutes
% 60 to get seconds

now you just gota find out how to use timers

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.