/*
   fileio3.cpp
   David Klick
   CIS 250
   1/31/05

   demonstration of random access file I/O
*/
#include <fstream>
#include <iostream>
using std::cout;
using std::endl;
using std::ifstream;
using std::ofstream;
using std::ios;

// this struct defines what the record is in the file
struct recType {
   int n;
   float x;
};

int main(void) {
   int i;
   recType rec;
   rec.x = 0.0f;

   // open output file as binary
   ofstream ofile("testfileio3.bin", ios::binary);
   if (!ofile) {
      cout << "Error: couldn't open output file" << endl;
      return 1;
   }

   // whole record is written at once to disk
   for (i=1; i<10; i++) {
      rec.n = i;
      ofile.write(reinterpret_cast<char *>(&rec), sizeof(rec));
      rec.x += 25;
   }
   ofile.close();

   // open file for input as binary
   ifstream ifile("testfileio3.bin", ios::binary);
   if (!ifile) {
      cout << "Error: couldn't open input file" << endl;
      return 2;
   }

   // find out how many records are in the file
   ifile.seekg(0L, ios::end);
   long numrecs = ifile.tellg() / sizeof(rec);

   // don't forget to get back to start of file
   ifile.seekg(0L, ios::beg);

   // read data in record-size chunks
   for (i=0; i<numrecs; i++) {
      ifile.read(reinterpret_cast<char *>(&rec), sizeof(rec));
      cout << rec.n << ", " << rec.x << endl;
   }
   ifile.close();

   return 0;
}