Using seekp( ) and seekg( ) to reverse characters in a file. - C++ File Stream

C++ examples for File Stream:stream

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Description

Using seekp( ) and seekg( ) to reverse characters in a file.

Demo Code

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
int main(int argc, char *argv[])
{
   long n, i, j;/*  ww  w  . java  2  s  . co  m*/
   char ch1, ch2;
   // Open the file for binary input and output operations.
   fstream finout("main.cpp", ios::in | ios::out | ios::binary);
   
   if(!finout) {
      cout << "Cannot open input file.\n";
      return 1;
   }
   n = 2;
   // Use random access to reverse the characters.
   for(i=0, j=n; i < j; ++i, --j) {
      // First, get the two characters.
      finout.seekg(i, ios::beg);
      finout.get(ch1);
      finout.seekg(j, ios::beg);
      finout.get(ch2);
      // Now, write them to the opposite locations.
      finout.seekp(i, ios::beg);
      finout.put(ch2);
      finout.seekp(j, ios::beg);
      finout.put(ch1);
      // Confirm the success of each read/write cycle.
      if(!finout.good()) {
         cout << "Error reading or writing characters.";
         finout.clear();
         break;
      }
   }
   finout.close();
   // Confirm that no errors occurred when closing the file.
   if(!finout.good()) {
      cout << "A file error occurred.";
      return 1;
   }
   return 0;
}

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